Milk yields of unimproved Awassi
sheep. The milk yields of unimproved Awassi ewes have been recorded in a
few flocks in Palestine, Lebanon, Syria, Turkey and Iraq under favourable
conditions of feeding and management. Hirsch (1933) estimated the annual milk yield of unimproved Awassi
ewes in bedouin and fellahin flocks in Palestine at 40 kg, to which about 20 kg
consumed by the lamb must be added (Mason, 1967).
In 1928-31 the
mean annual milk yields of Awassi flocks in three Jewish communal settlements
in Palestine (Aiyelet Hashahar, Tel Yosef and Beyt Alfa) ranged from 45 to 52
kg, exclusive of the milk suckled by the lambs, with only slight annual and
local differences. In another flock (in Merhavia), the annual milk yields, recorded
in 1932, varied between 30 and 150 kg, with an average of 63.5 kg.
With improved
feeding in Jewish settlements, the milk yields of unimproved sheep increased.
Thus, four flocks, purchased from Arab breeders, totalling 402 ewes, produced
an average of 128 kg of milk annually with a maximum yield of 320 kg, including
the milk consumption of the lambs.
In Lebanon, the
lactation yields were recorded in the course of six years (1960-65) for two- to
seven-year old ewes of an Awassi flock Trom unknown sources' kept at the Terbol
Animal Breeding Station on a high level of nutrition (Table 4-1).
In Syria the
average milk yield of well-fed Awassi ewes has been reported to be 168 kg
(Khouri, quoted by Mason, 1967). Erokhin (1973) gives an average lactation
yield of only 60 kg for Syrian Awassi ewes, but adds that high-yielding animals
produce 160-180 kg. At the University of Aleppo School of Agriculture, 60
Awassi yearling and 15 adult ewes acquired from bedouin in various parts of the
Syrian desert yielded 108 ±22 kg óf milk on average, with a range of from 30 to
190 kg, in a lactation of 193 ±16 days, in addition to the milk consumed by the
lambs in 16 days of full suckling, followed by 42 days during which they had
access to their dams only during the day. The milk produced at night during
this time was milked in the morning. Throughout the lactation period each ewe received 400 g of concentrates a day in addition to
grazing, and 300 g of
cottonseed hulls (Husnaoui & Fox, 1967).
In Turkey average
lactation yields ranging from 100 to 185 kg have been recorded in îvesi flocks at several experiment
stations. According to Yarkin and Eliçin
(1966), the milk yield, apart from the milk consumed by the lambs, for ívesi ewes of all ages averages
103.8 ±4.54 kg (25-180 kg). At the Çukurova
state farm, 268 îvesi ewes
produced 130 litres on average, including 48 litres consumed by the lambs;
record ewes yielded as much as 390 kg (Köseoğlu & Aytuğ, 1961; Yalçin, 1979). An experimental flock at the Aegean University farm
had an average lactation yield of 185 ±61.6 kg in the period 1959-63. The
record yield of a ewe of this flock was 345 kg (Sönmez & Wassmuth, 1964). At the Ereğli Animal Breeding Research Station in central Anatolia, the
lactation yield of ívesi ewes
averaged 125 kg in 1966/67 and 134 kg in 1967/68. At the same station îvesi ewes yielded 81.4 kg of
saleable milk if their lambs were weaned at 45 days, 72.2 kg with weaning at 60
days, and 54.0 kg at 75 days (Yalçin,
Aktas, & Sandikçioglu, 1968).
In the Ganziantep district, near the border with Syria, 225 îvesi ewes of three village flocks produced
119.5 kg of milk on average for each lactation (Sidal, 1973). The average
lactation yields of 13 different groups of îvesi ewes, reported in 1950-72, ranged from 73.5 to 273.7 kg, with
an overall average of 130.3 kg for each lactation for the 2 205 ewes recorded
(Lischka, 1976).
Yarkin and Eliçin (1966) claim that the
highest annual yield of îvesi ewes
is reached at five years, but in a flock of 83 îvesi ewes Aktas, (1970) found that the maximum lactation yield of
149.8 kg was attained at the age of four years. Of the total yield 65.4 percent
was obtained in the third month of lactation. After the weaning of the lambs at
the age of 75 days, the production of saleable milk came to 61 kg.
In Iraq the Awassi
is bred mainly for mutton and not for milk. The milk is usually consumed by the
farmers as their main source of animal protein. An Iraqi Awassi flock of 19
ewes, two to five years old, produced 105.9 kg of milk on average in a
lactation of 142 days (Eliya & Juma, 1970b). In a test with 31 Awassi ewes
of different ages, the milk yield in a lactation of 134 days averaged 115.7 kg.
The first lactation yield during the suckling period of 90 days, based on a
12-hour milking interval, was 75.3 kg, and with a four-hour milking interval,
86.1 kg. The largest yield was obtained during the third lactation at the age
of four years (Table 4-2).
Increase of milk yields in
improved Awassi. The relatively large lactation yields of unimproved Awassi
ewes maintained on a high plane of nutrition indicate that the improvement of
the Awassi in Palestine was based on the favourable genetic potential of the
foundation stock. Hence, selection for milk, accompanied by superior feeding
and management, led to a speedy increase in average yields and a corresponding
increase in the record yields of individual ewes.
The annual mean
breeding standard yields (Table 4-4) in milk-recorded Awassi flocks from 1937/
38 to 1964/65 as well as the annual mean yields of ewes registered in the flock
book and the record yield of individual ewes are shown in Table 4-3. The steep
increase in yield, figured in the 1955/56 report, resulted from a change in the
system of determining the quantity of milk consumed by the lamb (see pp.
184-186). It was found experimentally that the quantity had hitherto been
underestimated by about 10 percent and the recording has since been brought
into line with the requirements of the Study Commission on Sheep-Breeding of
the European Association for Animal Production.
The breeding
standard or maximum yield refers to the highest lactation yield of a ewe
hitherto attained during her productive life. It may be higher than, or
identical with, the recorded yield in a particular year and may increase in
subsequent years. In the past, the breeding standard or maximum yield served as
the basis for selection in Awassi flocks on the assumption that the maximum
lactation yield of a ewe under similar conditions of feeding and maintenance
prevailing throughout the flock to
which she
belonged indicated her genetic capability. The average of all maximum or
breeding standard yields of a flock expresses its general breeding standard in
any particular year. This is not identical with the mean yield of the flock
during that year, but it serves a useful purpose for comparison with other
flocks. The differences between the maximum or breeding standard yields of
flocks and their actual recorded yields are shown in Table 4-4 which refers to
the milk-recorded flocks for six different years.
In 1965/66, flock
book registration was discontinued and was replaced by the computer recording
of all ewes in milk-recorded flocks (Epstein, 1977). (See Table 4-5.)
In 1979/80 the
average lactation yield of the ewes of all milk-controlled Awassi flocks was
342 1. One ewe attained an annual yield of 1 463 1 (Fái, 1981).
The improvement in
milk production in the course of 30 years is reflected by the number of ewes
with yields above 400 kg. In 1942/43 only two ewes, or 0.08 percent of all
milk-recorded Awassi sheep, yielded more than 400 kg for each
lactation. In 1972/73 such ewes numbered 2 663, or 18.9 percent of all
milk-recorded animals. These are grouped in Table 4-6 according to adult,
two-year-old and yearling ewes and the type of farm where the flocks were
stationed.
In 1953/54 a flock
of 204 ewes attained a mean annual yield of 401 kg of milk for the first time.
In 1969/70 there were already two flocks with average annual yields of more
than 500 kg: one, composed of 780 ewes, with a mean
yield of 510 kg, and another with 1 220 ewes of 550 kg of milk. The dry matter
of the annual milk yield of these ewes represents approximately 150 percent of
their average live weight (Fái, 1972).
In 1971, 86 out of
188 Awassi ewes with maximum milk yields of more than 600 kg for each lactation
were stationed in the highest-yielding stud flock of the country ('Eyn Harod)
and 69 in the second-best one (Sde Nahum), while the remaining 33 ewes were
distributed among 15 other flocks.
In 1973/74 there
were five ewes with maximum lactation yields of over 1 000 kg of milk in the
'Eyn Harod flock, with a record yield of 1 282 kg for a two-year-old ewe. As
many animals lamb three times
|
TABLE 4-6. Number of ewes with
lactation records exceeding 400 kg, 1972/73 |
|||||||||||||
|
Type of farm |
No. of
flocks |
No.
of adult ewes |
No.
of two-year-old ewes |
No.of
yearlingewes |
Total
no. of ewes |
||||||||
|
Total |
Yield
above 400 kg |
% of
total |
Total |
Yield
above 400 kg |
% Of
total |
Total |
Yield
above 400 kg |
% of
total |
Total |
Yield
above 400 kg |
% of
total |
||
|
Communal farms |
23 |
7 463 |
1 835 |
24.59 |
2 869 |
482 |
16.80 |
2 068 |
213 |
10.30 |
12
400 |
2 530 |
20.40 |
|
Experimental farms and schools |
6 |
632 |
40 |
6.33 |
492 |
54 |
10.97 |
204 |
1 |
0.49 |
1 328 |
95 |
7.15 |
|
Private farms |
3 |
242 |
33 |
13.64 |
65 |
5 |
7.69 |
53 |
— |
— |
360 |
38 |
10.56 |
|
Total |
32 |
8 337 |
1 908 |
22.88 |
3 426 |
541 |
15.79 |
2 325 |
214 |
9.20 |
14
088 |
2 663 |
18.90 |
in the course of two years, the number of
ewes with annual milk yields exceeding 1 000 kg was ten. The high quality of
these ewes is illustrated by the consecutive lactation yields of three of them:
1) 1 005, 906 and 1 233 kg; 2) 630,954,1 075 and 1 011
kg; 3) 720,788,978,1 016, 688 and 599 kg. In the course of five years, from
1968/69 to 1973/74, the mean milk yields of the stud flock at 'Eyn Harod
increased by approximately 60 kg for each lactation
(Table 4-7).
| |||||||||||||||||||||||||
Milk yields of improved Awassi
sheep in Cyprus, Iran, Spain and Yugoslavia.
Cyprus. In Cyprus, improved
Awassi ewes imported from Israel or descended from imported Israeli stock had
the average completed lactation yields given in Table 4-8 in 1969/70, 1970/71
and 1971/72 (see also Table 4-78).
Iran. In
1965 and 1966, 42 male and 203 female Awassi lambs were imported into Iran from
improved flocks in Israel for pure-breeding and also for cross-breeding with
local Baluchi and Shal sheep. Table 4-9 gives the lactation yields for the
imported ewes and their descendents in Iran for 1967-70 (Wallach & Eyal, 1974). In 1968-70 the
average peak daily milk yields of two-year-old and adult ewes were as shown in
Table 4-10.
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
A report on the
development of sheep farming in the Qazvin area of Iran gives the data on the
minimum and maximum lactation yields of two-year-old and older Awassi ewes in
1967-69 (Table 4-11).
Spain. In 1971-79, 354 male
Awassi lambs were imported into Spain from a single stud in Israel. In 1971,
150 female Awassi lambs were imported from four different flocks, and in 1975
another 111 female lambs from the same stud that supplied the males.
Of the 150 female
lambs imported in 1971, 120 were pregnant and lambed as yearlings. Their mean
milk yields and length of first lactation in Spain and those of their
contemporary flock-mates in Israel were as given in Table 4-12.
Grouping according
to graduated lactation yields shows the percentages of the yearlings in Spain
(Carasso, personal communication, 1979) (Table 4-13).
The maximum
lactation yields in Spain of yearlings from each of the four flocks of Israeli
origin and their mean were as given in Tables
4-14 and 4-15.
| |||||||||||||||||||||||||
|
TABLE 4-12. Mean milk yields and
lactation lengths of Awassi yearlings in Spain and of their contemporary
flock mates in Israel |
|||||
|
Country |
No.
of yearlings |
No. of
lambings |
Mean
age at lambing (days) |
Mean
lactation yield (kg) |
Mean
length of lactation (days) |
|
Spain |
150 |
120 |
473 |
308 |
192 |
|
Israel |
263 |
146 |
471 |
168 |
149 |
|
Source: Carasso, 1974 |
|||||
| ||||||||||||||||||||||||||||||||||||
TABLE 4-15. Average milk yields of improved Awassi ewes
at different ages in Spain | |||||
|
Age |
Year |
Annual
lambings |
No.
of ewes |
Length
of lactation (days) |
Milk
yield (kg) |
|
Yearling |
1972/73 |
1 |
9 |
180 |
305 |
|
1973/74 |
97 |
191 |
278 |
||
|
1974/75 |
27 |
181 |
261 |
||
|
2-year-old |
1972/73 |
1 |
139 |
246 |
384 |
|
1973/74 |
49 |
219 |
340 |
||
|
1974/75 |
41 |
197 |
275 |
||
|
1972/73 |
2nd |
3 |
199 |
326 |
|
|
1973/74 |
3 |
210 |
346 |
||
|
1974/75 |
– |
– |
– |
||
|
Adult |
1973/74 |
1 |
107 |
214 |
307 |
|
2nd |
28 |
194 |
288 |
||
|
1974/75 |
1 |
72 |
205 |
283 |
|
|
2nd |
2 |
150 |
154 |
||
Yugoslavia. On a state farm
in the socialist sector of Macedonia, Yugoslavia, Awassi ewes imported from
Israel in 1969/70 at the age of eight to ten months on average produced 235 1
(124.9-420.0 1) of milk with a fat content of 6.8 percent (6.1-7.5 percent) in
209 first lactations of 136.5 days (41-230), shortened for managerial reasons.
Of the total production, 150.1 1 were milked and 84.9 1 suckled. The average
monthly percentages of the lactation yield were 24.1, 25.6, 22.0, 20.1 and 8.2,
respectively. The average daily yield was 1.7 1 and the maximum yield 3.1 1. In
summer the ewes were pastured and received an additional ration of
concentrates; in winter they subsisted on hay, straw, silage and concentrates.
As compared with the Awassi ewes' lactation yield of 150.1 1 of saleable milk,
local Pramenka ewes under the same conditions produced only 25 1 in addition to
the milk consumed by the lambs (Todorovski, Ristevski & Popovski, 1973a,
1973e).
On a farm in the
private sector of Macedonia, five Awassi ewes on average produced 224.6 1 of
saleable milk with 7.37 percent fat in the second, third and fourth months of
lactation in 1974. On the basis of this yield, Todorovski, Tanic and
Stojanovski (1975) estimated their total lactation yield at 421 1, a quantity
amounting to seven times the average yield of local Pramenka ewes.
Another farmer in
the private sector of Macedonia acquired seven Awassi ewes and one ram in 1974.
The sheep were kept on mediocre pasture, hay and concentrates. The breeding aim
was not to attain high milk yields but to enlarge the flock quickly. With three
lambings in two years, and in some instances two in one year, the flock
increased to 70 animals in 1977. In this year the milk of nine ewes was tested
in the second, third, fourth and fifth months according to international rules
for milk recording. For technical reasons the tests could not be performed
during the first and the last months of lactation. The milk yields on the
monthly test days were 2.525, 1.492, 1.537 and 1.0851, respectively, giving a
total yield of 199.17 1 with 7.73 percent fat in the four months of testing. On
the basis of this yield, the production of the ewes during the full lactation
period was estimated at 304.8 1 on average (Todorovski, Ristevski &
Popovski, 1979). This figure compares with a lactation yield of 72.5 1 with 5.4
percent fat for Macedonian Ovce Polje
(Pramenka) ewes (Taskovski, 1962), and 57.2 1 with 6.4 percent fat for
Sar Planina (Pramenka) ewes
(Todorovski, 1972).
Length and
course of lactation period. Average lactation lengths in
Awassi flocks throughout the range of the breed vary between 130 and 220 days.
In Syria, 15 adult and 60 yearling Awassi ewes had an average lactation period
of 193 ±16 days, ranging from 116 to 262 days (Husnaoui & Fox, 1967).
In the Ganziantep
district, 225 ívesi ewes
belonging to three village flocks had an average lactation length of 199 days
(Sidal, 1973). In an experimental flock of 268 ívesi ewes at the Çukurova
stock farm in Turkey, the average lactation length was 159 ±1.82 days (Köseoglu and Aytug, 1961), and at
the Ereğli Animal Breeding Research Station 185 days in 1966/67 and 212 days in
1967/68 (Yalçin and Akta§,
1969). In another experimental flock of Ívesi sheep at Izmir, Sönmez
and Wassmuth (1964) recorded an average length of 189.7 ±20.7 days in
162 lactations in 1959-63. While the correlation between length of lactation
and milk yield was positive, it was not high enough to warrant selection for
milk on the basis of lactation length alone, especially since the length of
lactation was greatly influenced by environmental factors, particularly by the
date of lambing. Early lambing Awassi ewes had considerably longer lactation
periods than those lambing late in the season. Yet in an analysis of 1 030
lactation records in the Çukurova
ívesi flock, Özcan and
Kaymaz (1968) found that while the total milk yield was significantly
correlated with lactation length, the date of lambing had no significant effect
on milk production.
In a trial with 19
Awassi ewes from four age groups kept on a high plane of nutrition at the Abu-Ghraib
Experiment Station in Iraq, an average lactation length of 142.0 days, ranging
from 119to 171 days, was recorded. The length of lactation increased from 133.2
days in two-year-old ewes to 157.3 days at four years and fell to 141.6 days in
five-year-old animals (Eliya & Juma, 1970b). As the number of ewes in each
group was very small (four to five), the usual positive correlation between
milk yield and length of lactation in Awassi sheep could not be established.
In a similar test
with 31 Awassi ewes conducted at Abu-Ghraib, the length of the lactation period
also rose from the second to the fourth year of age of the ewes and decreased
in the fifth year. The average lactation period was 134.9 days, varying between
94 and 157 days (Karam et al.,
1971). The duration of lactation had a highly significant effect on the total
milk yield. The daily milk yield, based on a 12-hour milking interval,
gradually declined after the second week of lactation (Fig. 4-1).
Figure 4-1
Average daily milk yields of Awassi ewes in Iraq in the
course of the lactation period. (Source: Karam et
al., 1971)
Awassi ewes
lambing late in the season, in February or March, often have their lactation
cut short by a reduced lambing interval. Vice versa, early lambing lengthens
the period of lactation. In addition, since a significant correlation exists
between the length of lactation and the annual milk yield of the Awassi, the
breeding season in the improved type has come to begin one or two months
earlier than that of the unimproved type.
Improved Awassi
ewes are usually dried off when their daily milk yield drops to below 200 g.
Milking is continued a little longer in only a few flocks in view of the very
high fat content of the milk toward the end of the lactation period.
To ascertain the
average length of lactation in the improved Awassi, Finci (1957) examined 1 718
completed lactations of 235 ewes, representing all age groups up to nearly 11
years. The average lactation period amounted to 200.8 days. Grouped according
to 25-day intervals, the numbers and percentages of lactations are set out in
Table 4-16.
The first
lactation period of two-year-old ewes is the shortest (182.4 days). From then
on it rises to the fifth lactation, which exceeds the first by 15 percent (27.4
days). Thereafter it decreases again, though
only slightly, the length of the seventh, eighth and ninth lactations being
still approximately 12 percent longer than that of the first.
Finci (1957) also
examined the course of 493 lactations at intervals of 30 days in ewes from
three different flocks (Table 4-17). In Cyprus the lengths of first, second and
subsequent lactations were recorded in Awassi ewes of improved dairy type
derived from Israel (Table 4-18).
In Iran, the
lactation lengths of three age groups of improved Awassi dairy ewes, imported
as lambs from Israel or descended from imported stock, were recorded in 1967-70
(Table 4-19).
| |||||||||||||||||||||||||||||
|
TABLE 4-19. Average length of
lactation of improved Awassi dairy ewes in Iran (days) |
|||||
|
Age of ewes |
1967 |
1968 |
1969 |
1970 |
Total |
|
Yearling |
180
(7) |
163
(10) |
203
(7) |
227
(70) |
214.9
(94) |
|
2 years |
227
(35) |
202
(49) |
239
(11) |
230
(34) |
219.3
(129) |
|
Adult |
— |
201
(43) |
240
(66) |
209
(48) |
219.8
(157) |
|
Note. Number of records in
brackets. |
|||||
|
Source: Wallach & Eyal, 1974 |
|||||
In Spain the
average lengths of completed lactation periods of yearling, two-year-old and
adult ewes imported from Israel were as given in Table 4-20. In Yugoslavia the
average length of lactation of 210 Awassi yearling ewes imported from Israel
was 136.5 days, ranging from 41 to 230 days. The lactation was shortened to
prepare the ewes for lambing at an earlier, economically suitable time. The
percentages of the monthly milk yields in the lactation period were as shown in
Table 4-21.
The fact that over
80 percent of the total lactation yield of ewes is produced in the first five
months —in addition to the desirable increase in the number of lambs — accounts
for the endeavour of many flock-masters, noted in recent years in Israel, to
obtain three lambings in two years or two lambings in one year instead of one
lambing a year. In two trials to obtain two crops of lambs in a year, Awassi
ewes that became pregnant soon after lambing without hormone application
yielded only 6-7 percent less milk for each lactation than the ewes that did
not conceive within 100 days after lambing (Morag & Eyal, 1971) (see also
p. 96, and Table 4-15).
In one of these trials,
83 ewes that had lambed during the first fortnight of September were joined by
rams immediately after parturition for a period of 100 days. The ewes were
milked twice a day and, concurrently with milking, suckled their lambs during
the night, until they were weaned at 40 days. Seventy-four of the 83 ewes
conceived in the course of 100 days, while nine did not. The mean milk yields
and lengths of lactation of the two groups were as given in Table 4-22.
In a highly
improved Awassi flock in Israel, three pregnancies in two years reduced the
average lactation length and yield as compared with one lambing a year, but
increased the total annual milk yield. In 107 instances of one full lactation a
year followed by two successive lactations shortened by early pregnancies, the
average lactation lengths and yields, recorded in 1969-74, were as given in
Table 4-23.
The weekly rate of
milk yielded during the first eight weeks after lambing varies with the age of
the ewe. Doron (1954b) recorded the total weekly production, including the milk
yielded to the pail
| |||||||||||||||||
TABLE 4-22. Mean milk yields and lactation lengths for
Awassi ewes | ||||||
|
Group |
Milk
yield (kg) |
Length
of lactation (days) |
||||
|
1st
lactation |
2nd
lactation |
Total |
1st
lactation |
2nd
lactation |
Total |
|
|
A |
249±7.6 |
220±7.1 |
469±10.7 |
151±2.6 |
144±3.1 |
295±5.1 |
|
В |
264±20.4 |
— |
— |
164
±13.1 |
— |
— |
|
Note.
A - those that conceived within 100 days of
lambing. | ||||||
TABLE 4-23. Average
lactation lengths and yields after a single yearly lambing followed by two
lambings in short succession | ||||
|
Lactation sequence |
Lactation
length |
Lactation
yield |
||
|
Days |
% of
preceding full lactation |
Kg |
% of
preceding full lactation |
|
|
Preceding full lactation |
258.4 |
100.0 |
556.7 |
100.0 |
|
1st shortened lactation |
156.2 |
60.4 |
425.0 |
76.3 |
|
2nd shortened lactation |
160.2 |
62.0 |
339.2 |
60.9 |
TABLE 4-24. Milk yields of Awassi ewes in the first eight
weeks after lambing (% of 1 st
week's yields) | |||||||||
|
Age of ewes |
No.
of ewes |
Week |
|||||||
|
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
||
|
2 years (1st lambing) |
12 |
100 |
124 |
142 |
136 |
154 |
154 |
152 |
136 |
|
3 years (2nd lambing) |
8 |
100 |
119 |
128 |
117 |
130 |
134 |
132 |
122 |
|
Over 5 years |
18 |
100 |
103 |
111 |
119 |
121 |
126 |
126 |
109 |
and the
residue suckled by the lambs, at the Acre Experiment Farm in the two seasons of
1952 and 1953. The yields, expressed as percentages of the first week's record,
were as given in Table 4-24.
The height of
production, at every age, is reached in the sixth week, after which weekly
yields decrease. Doron (1954b) concluded from the records that young ewes,
lambing for the first and second time, increase their yields more speedily and
sharply than older ewes. This, of course, may also be expressed the other way
round, namely that older ewes attain a relatively high rate of production soon
after lambing.
After the second
month of lactation the milk yield of Awassi ewes decreases rapidly. In a test
of 350 two- to seven-year-old ewes in 1953-58 and of 145 ewes of the same age
groups in 1959/60, Goot (1966) established that the daily yield of milk falls
in the third month to about 80 percent and in the fourth month to 52 percent of
the mean yields of the first two months. (See Table 4-25 and Fig. 4-2. )
The treatment of
lactating ewes with progesterone and PMS causes a serious depression
in milk yield.
This is attributed to the inhibitory effect of progesterone on lactation and to
the promotive effect of PMS on
follicle development, releasing oestrogen which is also an inhibitor of milk
secretion. Hence, these hormones are but rarely applied to adult ewes in Awassi
dairy flocks. In a trial to obtain two lambings a year in Awassi ewes, hormone
treatment from the twelfth to the eighteenth day after lambing reduced the milk
yield by 17 percent in those ewes that conceived, and by 26 percent in those
that did not conceive (see p. 96, and Tables 4-22 and 4-23) (Morag & Eyal,
1971).
In an Awassi flock
at the Ereğli Animal Breeding Research Station in Turkey, the weaning of İvesi
lambs at 45,60 or 75 days had no effect on lactation
length (Yalçin and Akta§,
1969). However, shorter suckling regimes did influence the length of lactation
of Israeli Awassi ewes in Cyprus, where the lactation lengths under three
different suckling regimes—the removal of lambs immediately after birth,
weaning at two days and weaning at 35 days — were recorded (Table 4-26).
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||
Figure 4-2. Average daily milk yields of 2-and
3-year-old Awassi ewes during first 4 months of lactation period. (Source: Goot, 1966)
Maximum daily milk yields. In Syria the maximum 24-hour milk
production of a ewe with the highest lactation yield in the desert-bred Awassi
flock acquired by the University of Aleppo School of
Agriculture was 1.89 kg (Husnaoui & Fox, 1967).
In an İvesi flock at the
Faculty of Agriculture of the Ege University Izmir in Turkey, the average peak
milk yield in a day was 1.77 kg (Sönmez & Wassmuth, 1964).
In Israel, until
1955/56, the maximum milk yield of improved Awassi ewes in 24 hours was 4.5 kg;
of 989 ewes belonging to four highly improved flocks only 24 (or 2.4 percent)
exceeded a yield of 4 kg in 24 hours. In 1955/56, several ewes attained maximum
yields of up to 6 kg a day (Finci, 1957). In 1973/74 and 1974/75, an improved
flock (I) with an average lactation yield of 310 kg for ewes of all ages, and
another flock (II) with an average yield of 427 kg, recorded in 1973/74,
included the numbers of ewes with maximum yields of 4 kg and more in 24 hours
given in Table 4-27.
TABLE 4-27. Numbers of ewes with maximum milk yields of 4 kg/day and
more in two Awassi flocks | |||||||||||
|
Flock age |
No. of lactations |
Maximum milk yield/day (kg) |
|||||||||
|
4.0-4.9 |
5.0-5.9 |
6.0-6.9 |
7.0 and more |
||||||||
|
No. |
% |
No. |
% |
No. |
% |
No. |
% |
||||
|
I |
Yearling |
138 |
— |
— |
— |
— |
— |
— |
— |
— |
|
|
2-year-old 1st lambing |
93 |
— |
— |
— |
— |
— |
— |
— |
— |
||
|
2-year-old 2nd lambing |
128 |
2 |
1.56 |
— |
— |
— |
— |
— |
— |
||
|
Adult |
658 |
32 |
4.86 |
1 |
0.15 |
— |
— |
— |
— |
||
|
Total/Average |
1 017 |
34 |
3.34 |
1 |
0.10 |
— |
— |
— |
— |
||
|
II |
Yearling |
473 |
59 |
12.47 |
3 |
0.63 |
— |
— |
— |
— |
|
|
2-year-old 1st lambing |
121 |
39 |
32.23 |
13 |
10.74 |
2 |
1.65 |
— |
— |
||
|
2-year-old 2nd lambing |
225 |
78 |
34.67 |
20 |
8.89 |
2 |
0.89 |
— |
— |
||
|
Adult |
853 |
294 |
34.47 |
89 |
10.43 |
12 |
1.41 |
2 |
0.23 |
||
|
Total/Average |
1 672 |
471 |
28.17 |
125 |
7.48 |
16 |
0.96 |
2 |
0.12 |
||
Seventy-five and a
half percent of the total 2 689 maximum milk yields of 4.0 kg and more a day
were attained at the first milk recording of the lactation period, 18.6 percent
at the second, 4.4 percent at the third, and 1.5 percent at the fourth
recording.
In 1977 a
two-year-old stud ewe in her second lactation produced a record yield of 8.0 kg
of milk in 24 hours in the second month of recording. As the breeder doubted
the exactness of this record, the ewe's milk was again weighed the following
day when the yield was 7.8 kg.
From a comparison
of the correlation coefficient between the total lactation yield and the daily
maximum yield with the correlation coefficient between lactation yield and
length of lactation, Finci (1957) arrived at the conclusion that the maximum
yield in 24 hours provided the basis for a more precise estimate of the milking
capacity of an improved Awassi ewe than did the length of the lactation period.
Lifetime milk yields. The
total milk production in the lifetime of Awassi ewes has continuously increased
in Israel in the course of improvement of the breed. Over 20 years ago, Finci
(1957) recorded the life performance of 739 ewes with six to ten completed
lactations chosen at random from 11 flocks and registered in the flock book
(see Chapter 7). At the beginning of their first lactation the ewes had reached
the age of two; at the time of investigation they were 7-11 years old. (See
Table 4-28.) Finci also recorded the lifetime yields of eight selected ewes,
5-12 years old with 4-11 lactations, their average annual performance and their
record daily and annual yields (Table 4-29).
In an Awassi flock
with high milk yields, a total of 151 ewes were culled in 1974 after completion
of one to ten lactations, with an average of 4.22 lactations at culling. The
mean and maximum lifetime yields of these ewes, arranged according to number of
lactations prior to culling, were as given in Table 4-30. The maximum lifetime
yield of 728 kg in one lactation was attained by a ewe
that had lambed at two years; that of a yearling ewe was 675 kg.
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Influence of age on milk
production. The influence on annual milk yields of the age of Awassi ewes
was investigated by Finci (1957) in two highly improved flocks. Ewes with seven
to nine consecutive lactations were classed in nine groups comprising a total
of 1 718 lactations, each age group up to the seventh lactation including over
200, the eighth 124, and the ninth 61 lactations. (See Table 4-31.)
The data show an
increase in milk yields from the first to the fourth lactation and a gradual
decline occurring up to the ninth. However, the older animals, probably owing
to an earlier culling of the poorer milkers, still yielded more on average than
the two-year-old ewes at their first lactation.
In an experimental
flock of improved Awassi sheep, Goot (1966) recorded average lactation yields
in 1953-62 (Table 4-32). These show an increase up to the third lactation and a
gradual decrease thereafter. In contrast with Finci's records, the older ewes
did not reach the yields of the two-year-olds.
In 1973/74,
computer records of 2 669 lactation yields in one of the two highly improved
flocks investigated by Finci (1957) (Table 4-31) — the other one having
meanwhile been crossed with East Friesian—showed a rise in yields from the
first lactation of yearling ewes to the third lactation and a decline in
subsequent yields. Since the computer records do not go back further than the
year 1969/70, the data comprise only a small number of ewes with more than six
completed lactations, the records of which were obtained directly from the flock-master.
In the course of the two decades since Finci's study, the lambing of yearling
ewes was introduced in Awassi flocks in Israel. The first-lambing ewes
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
have
therefore been separated into yearlings, having lambed before the end of their
second year of life, and two-year-old ewes with later lambings. Records of
shortened lactations owing to two lambings in a year have been excluded to
prevent a distortion of the typical sequence. (See Table 4-33.)
Finci (1957) noted
that an Awassi ewe's milking potential may be estimated from her first
lactation yield at the age of two. An age correction factor of 1.47 will
indicate her probable milk yield at the fourth lactation, which, on average, is
the highest one and as such may be used as a basis for selection. Ewes with
high first lactation yields usually retain their high milking capacity up to
the seventh lactation; even the few available eighth and ninth lactation
yields, although considerably lower than earlier ones, still show positive
correlation coefficients with the first lactation yield. More recent records
indicate a markedly smaller age correction factor than that claimed by Finci
for an earlier period.
Body size and milk yield. Taller
ewes on average produce more milk than shorter ones. Finci (1957) found that
the correlation coefficient between height at withers and the maximum (breeding
standard) milk yield of Awassi ewes was significant only at the 5-percent
level, whereas that between withers height and the fourth lactation yield was
significant at the 1-percent level. In Cyprus Fat-tailed sheep the correlation
coefficient between height at withers and milk production was also only
slightly significant (Finci, 1938).
The correlation
between the body weight of Awassi ewes, recorded in November and December in
the course of several years, and the maximum lactation yield was low but still
significant at the 1 -percent level, while that between weight and the fourth
lactation yield was of an insignificant value (Finci, 1957). Goot (1966), in
1960-61, could not find any correlation between the body weight, taken three
days after lambing, of 81, 2- to 7½-year-old
improved Awassi ewes of an experimental flock and their yields of marketable
milk. This is attributed to the variable nutritional and physiological
conditions in the course of the year and in different years.
Yet the fact that
breeding for milk in the improved Awassi for more than four decades has led to
a very large increase in the body weight of ewes, that is, from about 40 kg to
60-80 kg, indicates that higher milk yields require a larger body, more
especially larger heart, lungs and udder and a larger capacity of the digestive
organs, capable of coping with larger quantities of feed. The larger body of
improved Awassi ewes, acompanying increased milk yields, is also indicated by
higher birth weights as compared with those of the unimproved type
(see Fig.
3-16, p. 110).
Fat content of
Awassi milk. The milk of unimproved Awassi ewes contains 7.5
percent fat on average (Mason, 1967). In Anatolia in 1966-68, the milk of an İvesi flock at the
Ereğli Animal Breeding Research Station
contained 7.0 percent fat, while the total average fat production for a
lactation was 9.4 kg (Yalçin and Aktaş, 1969). Eliçin (1964,
quoted by Eliya & Juma, 1970b) recorded a smaller fat percentage in İvesi
milk in Turkey, namely 6.13 percent.
At the Abu-Ghraib
Experiment Station in Iraq, Nejim (1963) tested the fat percentage of the milk
of a flock of Awassi ewes at weekly intervals in the last three months of the
lactation period of 1960/61 (Table 4-34). During these months the average fat
content was 7.7 percent, ranging from 5.3 to 10.0 percent in the different test
weeks. In 1961/62 the fat content of the milk of the same flock was tested
during the whole lactation of 5½ months.
The average was 6.88 percent, ranging from 4.6 to 11.8 percent in the 21 test
days of the period.
Eliya and Juma
(1970b) recorded considerably smaller fat percentages of the milk of two- to
five-year-old Awassi ewes in Iraq (Table 4-35). The effect of a ewe's age on
lactation yield, which ranged from 102.5 to 109.0 kg, was not found to be
significant, but this may be because of the small number of ewes in the test.
In Palestine,
during the period 1928/29-1930/31 when the local Awassi breed was still on the
threshold of improvement, the fat content of the milk of two flocks belonging
to communal settlements ranged from 6 percent to 8 percent (Hirsch, 1933). For the next 20 years it
remained nearly at the same level, although a slight falling off was already
noticeable with the steadily increasing milk yields of the ewes. Since then,
however, breeders of the Awassi in Israel in the selection of breeding stock
have paid all their attention to the quantity of milk and have neglected fat
content. As a result, the latter markedly decreased with increasing milk
yields; yet the total fat output for each lactation
has become larger because the effect of the increased quantity of milk on total
fat production has outweighed the reduction in percentage.
The fat percentage
of 1 740 samples of mixed morning and evening milk (mean = 7.54 percent) tested
at a central collecting station in 1942/43 showed the range given in Table
4-36.
Finci (1957)
reported that in 1950/51 the milk from 612 milk-recorded ewes had a fat content
of 6.98 percent. In 1953/54 the milk of 498 ewes, which had been selected from
11 flocks for the
| |||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||
production of stud rams and which had a maximum lactation yield of
not less than 370 kg, was tested at 7.06 percent on average. The mean annual
butterfat percentage, periodically tested during the entire lactation period,
showed considerable differences between the milk of individual ewes (Table
4-37).
With milking
intervals of unequal length, the fat content of the milk obtained after the
shorter interval is higher than the fat percentage of the milk yielded after
the longer interval.
The effect on fat
percentage of the quantity of milk yielded at the time of testing is shown by a
comparison between ewes giving up to 400 g of milk and others yielding more than 450 g at the primary milking. Of the former,
195 samples tested yielded 6.23 percent, and 212 samples of the latter 5.73
percent on average, a difference of 0.5 percent in favour of the milk from the
ewes with the lower milk yields (Eyal, Volcani & Sharav, 1958).
A test on the
effect of the age of Awassi ewes on the fat content of their milk, made with a
small number of animals at regular intervals during six weeks after weaning the
lambs, showed a lower fat percentage in the milk of first-lambing ewes than in
that from older animals, but the difference was statistically insignificant
(Nitsan & Volcani, 1960) (Table 4-38).
In improved Awassi
sheep in Israel there has been a continuous fall in the fat percentage of milk
over the last 40 years (Table 4-39). The fall from 7.54 percent in
1943/44-1945/46 to 5.44 percent in 1976/77 in the fat content of Awassi milk
delivered to central collecting stations in Israel is not only a result of the
neglect of this economically important element in the selection of breeding
stock. Partly it must also be attributed to the general use of milking machines
in improved flocks and the cessation of secondary hand milking. The rich milk
thus retained in the udders is left to the lambs for residue suckling. In
Yugoslavia the average fat content of the milk of 229 lactations of Awassi ewes
imported from Israel in 1969 and stationed in a socialist cooperative combine
was 6.84 percent, ranging from 6.1 to 7.5 percent (Todorovski, Ristevski &
Popovski, 1973a). On a peasant farm near Skopje in northern Makedonija, the
average fat content recorded in four tests of Awassi milk was 7.4 percent
(Todorovski, Tanić & Stojanovski,
1975). This high fat percentage is attributed to the feed, which in Yugoslavia
consists mainly of high-quality roughage and good grazing, whereas in Israel
pastures are poor and the rations of Awassi sheep contain large portions of
concentrates (Epstein, 1977).
| |||||||||||||
The differences in
fat percentage of the milk between different improved flocks of similar
breeding and feeding are relatively slight. Finci (1957), referring to the
statistically insignificant differences in the mean fat content of the milk
between two flocks—20 milk-recorded animals with a mean of 6.72 percent in one
and 46 similar ewes with 7.37 percent in the other—attributed this to the fact
that no selection for the increased fat content of Awassi milk had been carried
out in Israel. An additional cause, no doubt, is the use of rams from a single
flock. However, in view of the well-established negative correlation between
the quantity of milk and the fat percentage, differences in the average milk
yield of ewes from different flocks doubtless affect the mean fat percentage ; this may also be influenced by differences in
the feed as evidenced by the high fat percentage in the milk of Awassi sheep
from Israel in Yugoslavia (see p. 146).
In 1976/77 the
average annual fat content of the milk of 27 improved Awassi flocks delivered
to central collecting stations in Israel ranged from 4.85 to 6.04 percent, with
an average of 5.44 percent (see Table 4-40).
Changes in fat content of Awassi
milk in the course of a lactation period. At Abu-Ghraib in Iraq the fat
content of 145 samples of milk from 19 hand-milked Awassi ewes in a period of
16 weeks increased from 3.96 percent in the first week to a maximum of 6.66
percent in the thirteenth week. Thereafter it fell to 4.95 percent at the end
of the test, the average for the whole period amounting to 5.25 percent (Eliya,
Juma & Al-Shabibi, 1972).
Generally the fat content of the milk of Awassi ewes rises from the
beginning to the end of the lactation period by approximately 33 percent, a
rise similar to that encountered in dairy cows in the course of their
lactation.
The average monthly fat content of Awassi milk derived from morning and
evening milkings was recorded by Kern (1953) at a central dairy in Palestine in
1943/44-1945/46 and in the whole of Israel in 1949/50 and 1950/51. The average
fat content of all Awassi milk deliveries of a total of 1 934 tonnes, received
at central dairies in 1976/77, shows a sharp decline in
monthly fat percentages in the course of 25 years. (See Table 4-41.)
The fact that in the early
years of Awassi improvement the fat percentage of the milk delivered to the
central dairies was higher in the first months than at the height of the
lactation period is attributed to the then-prevailing system of lamb rearing.
In the first few weeks of their lives, the female lambs and the few males
required for breeding were allowed to suck freely on the return of the ewes
from pasture or during the night. Only the very rich milk left over was milked
and included in the deliveries to the central dairies.
The tests in 1976/77 show two breaks in the rising line of fat percentage from the lowest in November to the highest in September, namely in May and August. The fall in May is due to the lambings of yearling ewes in April, and that of August to the second lambing of a certain number of adult ewes that had already lambed the previous October or November.
The tests in
1976/77 show two breaks in the rising line of fat percentage from the lowest in
November to the highest in September, namely in May and August. The fall in May
is due to the lambings of yearling ewes in April, and that of August
to the second lambing of a certain number of adult ewes that had already
lambed the previous October or November.
| |||||||||||||||||||||||||||
|
Year |
1943/44-1945/46 |
1949/50 |
1950/51 |
|
1976/77 |
||
|
Month |
Fat |
Milk in 1 000 kg |
Fat |
Milk in 1 000 kg |
Fat |
Milk in 1 000 kg |
Fat |
|
October |
— |
— |
— |
— |
— |
9.6 |
5.88 |
|
November |
— |
1.5 |
7.35 |
— |
— |
38.5 |
4.83 |
|
December |
6.70 |
29.3 |
7.40 |
17.8 |
7.29 |
141.8 |
4.86 |
|
January |
7.30 |
167.2 |
7.52 |
141.3 |
6.88 |
204.3 |
5.04 |
|
February |
6.90 |
245.3 |
7.47 |
358.2 |
6.57 |
244.3 |
5.23 |
|
March |
6.80 |
431.2 |
6.83 |
617.0 |
6.29 |
282.9 |
5.35 |
|
April |
6.70 |
412.6 |
6.55 |
556.7 |
6.59 |
220.1 |
5.68 |
|
May |
8.20 |
319.6 |
7.54 |
415.4 |
7.29 |
204.8 |
5.63 |
|
June |
8.40 |
198.3 |
7.94 |
254.5 |
7.60 |
175.1 |
5.80 |
|
July |
8.70 |
98.2 |
8.05 |
132.3 |
7.83 |
117.1 |
5.96 |
|
August |
9.11 |
22.9 |
8.08 |
32.4 |
7.53 |
69.5 |
5.86 |
|
September |
10.00 |
1.3 |
8.58 |
1.4 |
7.33 |
26.2 |
6.02 |
Solids-not-fat
in Awassi milk. In a test of 1 740 samples of milk in
1942/43, Kern (1953) found that over 94 percent fell within the range of
10.4-11.4 percent solids-not-fat, with an average of 10.9 percent. Only 0.3
percent of the samples deviated from the mean by more than 1 percent. (See
Table 4-42.)
Tests of several thousand samples of Awassi
milk in a central dairy in Palestine in 1942/43-1945/46 showed that the monthly
variations in the solids-not-fat content were also only slight (Table 4-43).
While the total
solids-not-fat content of the milk varied but little, generally or monthly, the
monthly variations between the different constituents of the solids-not-fat
were considerable.
Variations in the
fat content of Awassi milk seem to affect the percentage of solids-not-fat more
than they affect the percentage of total solids. In an Awassi flock at the
Abu-Ghraib Experiment Station in Iraq, Nejim (1963) analysed the total solids
and solids-not-fat content in the bulk milk of ewes in two consecutive years.
In the first year weekly samples were taken only in the last three months of
the lactation period, that is, from May to July; in the second year the milk
was tested for the full lactation period of 5V months, from the end of December
to the beginning of June. While the average contents of total solids were
similar in both seasons, namely 19.78 percent (18.19-24.36) and 19.87 percent
(17.34-24.56), the solids-not-fat content differed markedly, amounting to 11.99
percent (10.09-14.36) in the last three months of the first lactation tested,
and 12.99 percent (11.11-13.92) during the full lactation of the following
year, the difference being mainly owing to the different fat content of the
milk (7.70 and 6.88 percent, respectively). Table 4-44 gives the average
monthly percentages of total solids and solids-not-fat during the two seasons.
In a further test
conducted at Abu-Ghraib over 16 weeks, the average percentage of total solids
in 145 samples of milk from 19 Awassi ewes was considerably lower, that is,
16.18 percent, varying between 14.01 and 18.01 percent, the difference of 3.6
or 3.7 percent from the earlier tests being attributed to a different method of
sampling. Like the fat content of the milk, the percentage of total solids
increased with advancing lactation to a maximum during the thirteenth week. The
solids-not-fat content of the milk ranged from 10.07 percent in the second week
to 11.66 percent in the sixteenth week of lactation and averaged 10.92 percent
(Eliya, Juma & Al-Shabibi, 1972).
Morning milk,
obtained 12 hours after the evening milking, contains a smaller percentage of
solids-not-fat and a higher percentage of fat than evening milk. The
differences, statistically highly significant, were established by Nitsan and
Volcani (1960) in the course of six consecutive weeks in an analysis of the
morning and evening milk of 16 ewes of different ages that had lambed in the
same month (Table 4-45).
The difference in
the solids-not-fat content of Awassi milk between the primary and secondary
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||
TABLE 4-45. Composition
of morning and evening milk of Awassi ewes | |||||||||||
|
Lactation |
No. of ewes |
Milk yield |
Total solids |
Solids-not-fat |
Fat |
Protein |
|||||
|
Morn. (g) |
Even. (g) |
Morn. (%) |
Even. (%) |
Morn. (%) |
Even. (%) |
Morn. (%) |
Even. (%) |
Morn. (%) |
Even.
(%) |
||
|
1st |
4 |
1 130 |
690 |
17.1 |
17.2 |
11.3 |
11.8 |
5.7 |
5.4 |
5.0 |
5.1 |
|
2nd |
6 |
1 220 |
930 |
17.5 |
17.5 |
11.3 |
11.6 |
6.3 |
6.1 |
5.6 |
5.4 |
|
4th |
6 |
1 160 |
970 |
17.4 |
17.4 |
11.1 |
11.5 |
6.3 |
5.9 |
5.1 |
5.1 |
yields has
been examined by Sharav (1971) during three 20-day periods of alternate machine
milking and machine plus hand milking in two groups of non-suckling ewes in
Israel. The results showed that while the fat content of the primary milk is
lower than that of the secondary milk, the reverse applies to the
solids-not-fat percentage (see Table 4-65).
Proteins and
lactose in Awassi milk. Awassi milk contains 5.56 percent
protein on average. Kern (1953) recorded the monthly variations in the casein
content of 1 740 samples of Awassi milk in 1942/ 43, and of total proteins,
casein, albumin and globulin in several thousand samples in 1943/44-1945/46
(Table 4-46). During the lactation period, the total protein content of Awassi
milk rises from approximately 5 to 7 percent, while the casein content
increases merely from 4 to 5 percent.
TABLE 4-46. Monthly variation in the
protein contents of Awassi milk | |||||
|
Month |
1942/43 |
|
1943/44-1945/46 |
|
|
|
Casein (%) |
Total proteins (%) |
Casein (%) |
Albumir and globulin |
Casein as % of total proteins |
|
|
December |
— |
5.08 |
3.83 |
1.25 |
75.4 |
|
January |
4.13 |
4.78 |
3.68 |
1.10 |
77.0 |
|
February |
4.16 |
5.27 |
4.24 |
1.03 |
80.5 |
|
March |
4.23 |
5.10 |
3.92 |
1.18 |
76.9 |
|
April |
4.32 |
5.29 |
4.10 |
1.19 |
77.5 |
|
May |
4.39 |
5.56 |
4.15 |
1.41 |
74.6 |
|
June |
4.38 |
6.09 |
4.79 |
1.30 |
78.7 |
|
July |
4.39 |
6.05 |
4.62 |
1.43 |
76.4 |
|
August |
4.76 |
6.18 |
4.63 |
1.55 |
74.9 |
|
September |
— |
7.17 |
4.84 |
2.33 |
67.5 |
At the Abu-Ghraib
Experiment Station in Iraq, the average protein content of the bulk milk of an
Awassi flock, tested at weekly intervals in the last 2½ months of the lactation period, amounted to 6.18 percent
(5.85-6.50). The monthly averages were: March 5.85 percent, April 6.23 percent,
May 6.31 percent, and June 5.85 percent (Nejim, 1963).
The average
lactose content of the milk of the same flock, recorded by Nejim (1963) during
a full lactation period of 5½ months, was
5.75 percent, ranging from 4.65 to 7.04 percent.
Ash content of
Awassi milk. The ash content of Awassi milk has been analysed
by Nejim (1963) in a flock at the Abu-Ghraib Experiment Station at weekly
intervals in two consecutive years,
in the first season in the last three months of the lactation period and in the
following season for the whole lactation. In the first season the milk
contained 0.886 percent ash on average, ranging from 0.775 to 0.975 percent; in
the following full lactation the average ash content was 0.928 percent, varying
between 0.864 and 1.018 percent. The average monthly percentages of total ash,
calcium oxide (CaO) and phosphorus pentoxide (P205) in
the milk and ash, and the ratio of calcium oxide (= 1) to phosphorus
pentoxide are given in Table 4-47. The CaO and P205
contents of the milk increased until the lambs were about four months old and
then showed a slight decline.
Nejim
(1963) notes that the milk of Awassi ewes contains about 55 percent more CaO
and 45 percent more P205 than cow milk. Awassi
milk contains 112.4 mg of chlorine for every 100 g on average, ranging from 96 to 147 mg
(Kern, 1953).
Specific
gravity, freezing point, acidity, viscosity, flavour and fat composition of
Awassi milk. The specific
gravity (SPG) of Awassi milk depends on the proportions between the
various constituents, namely, water (SPG 1.000), fat (SPG 0.93), proteins (SPG
1.346), lactose (SPG 1.666) and ash (SPG 5.5) and on their individual and
seasonal variations. Therefore the average specific gravity of Awassi milk
differs in different months of the year. It is especially affected by the
variable fat content of the milk. Kern (1953) recorded an average specific gravity of 1.0371 in
Palestine in 1943/44-1945/46, with the monthly variation given in Table 4-48.
A similar
variability in the specific gravity of Awassi milk in different months is
indicated by the data recorded for an Awassi flock at the Abu-Ghraib Experiment
Station in Iraq at weekly intervals in the last three months of the lactation
in 1960/61 and the full lactation in 1961/62 (Table 4-49). During
TABLE 4-47. Average
monthly percentages of total ash, CaO and P205 in milk
and ash, and CaO-P205 ratio in Awassi milk in Iraq | ||||||||||||
|
Month |
First season |
Second season |
||||||||||
|
Ash |
CaO in |
P205 in |
CaO: P2O5 |
Ash |
CaO in |
P205 in |
CaO: P205 |
|||||
|
milk |
ash |
milk |
ash |
milk |
ash |
milk |
ash |
|
||||
|
December |
— |
— |
— |
— |
— |
— |
0.905 |
0.256 |
28.3 |
0.300 |
33.1 |
1.17 |
|
January |
— |
— |
— |
— |
— |
— |
0.898 |
0.287 |
32.4 |
0.339 |
38.1 |
1.18 |
|
February |
— |
— |
— |
— |
— |
— |
0.879 |
0.304 |
34.6 |
0.354 |
30.8 |
1.16 |
|
March |
— |
— |
— |
— |
— |
— |
0.980 |
0.301 |
30.6 |
0.354 |
36.2 |
1.18 |
|
April |
0.852 |
0.275 |
32.3 |
— |
— |
— |
0.948 |
0.299 |
31.6 |
0.311 |
32.8 |
1.04 |
|
May |
0.867 |
0.315 |
36.4 |
0.328 |
38.0 |
1.04 |
0.962 |
0.277 |
28.8 |
0.284 |
29.6 |
1.03 |
|
June |
0.911 |
0.289 |
31.8 |
0.316 |
34.9 |
1.09 |
1.018 |
0.258 |
— |
0.231 |
22.7 |
0.90 |
|
July |
0.887 |
0.285 |
32.0 |
0.315 |
35.5 |
1.11 |
— |
— |
— |
— |
— |
— |
| |||||||||||||||||||||||||||||||||
the first
season of lactation the average specific gravity of the milk was 1.0338 (1.0280-1.0378)
and during the second season, 1.0366 (1.0305-1.0415) (Nejim, 1963).
In another test of
145 samples of milk from 19 Awassi ewes at Abu-Ghraib, the specific gravity of
the milk ranged from 1.0370 during the second week to 1.0408 in the sixteenth week
of lactation (Eliya, Juma & Al-Shabibi, 1972).
The
specific gravity of Awassi milk in conjunction with the fat percentage lends
itself to an approximate estimate of the solids-not-fat content of the milk
according to the following formula proposed by Kern (1953).
Specific gravity
and fat percentage are relatively easy to ascertain, whereas the assessment of
the solids content necessitates the drying of the sample and an elaborate
chemical analysis.
In an
investigation of the freezing point of Awassi milk in Iraq, Eliya, Juma and
Al-Shabibi (1972) recorded an average of-0.5699°C. As freezing point depression
largely depends on the water content of the milk, its variation at different
stages of the lactation period followed the trend of the total solids content.
Awassi milk has a relatively high naturel acidity. In 52 samples recorded at
a central dairy in Palestine the acidity varied between 6.2 and 8.2
Soxhlet-Henkel degrees, with an average of 7.02. The average monthly differences
in the acidity of Awassi milk were recorded during the period 1943/44-1945/46
(Table 4-50).
The average titratable acidity of
the milk of an Awassi flock at the Abu-Ghraib Experiment Station, measured at
weekly intervals in a full lactation period of 5V months, was 0.22, ranging
from
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||
0.10 to 0.29.
The pH, determined from the
second month to the end of the lactation, was 6.65, varying between 6.46 and
6.90. The average monthly titratable acidity data show a reduction and the pH data an increase toward the end
of the lactation (Table 4-51) (Nejim, 1963).
In another test of
the milk of 19 Awassi ewes at Abu-Ghraib, the hydrogen-ion concentration was
6.53 in the first week of lactation and 6.87 in the second week. The average
for the whole lactation of 16 weeks was 6.74 (Eliya, Juma & Al-Shabibi,
1972).
The changes in
acidity are a result of the changing percentage of solids, more especially
casein, in the milk. In general, the natural acidity of fresh Awassi milk is
considerably higher than that of the milk of Friesian cows, mainly owing to the
higher protein and mineral content of the former. Yet this higher apparent
acidity does not cause Awassi milk to sour sooner than cow milk. In fact,
bacterial growth is slower in Awassi than in cow milk, since the high
percentage of solids acts as a preservative.
Owing to their
relatively high fat and protein content, and probably also to their high
riboflavin content, Awassi milk and whey have a yellowish colour. Awassi milk
has a fatty and adhesive taste. If milked by hand, it often has a peculiar
taste and flavour. Its high viscosity renders the ascent of the fat globules
very slow and centrifugation difficult, although the fat globules are twice as
large as in the milk of Friesian cows. The difficulty can be overcome by the
addition of water or skimmed cow milk to Awassi milk prior to centrifugation.
The composition of
the butterfat of Awassi milk varies from month to month. During the first five
or six months of the lactation period the fat of Awassi milk is particularly
rich in butyric acid; toward the end of lactation the butyric acid decreases.
The melting point of the fat falls from about 32°C in December to 30°C in
March, whence it rises to about 38°C in August and September. Again, the
temperature at which Awassi milk fat solidifies rises from 14.5-17.5°C in the
months of December to April to 18.6-20.4°C in the period from May to September
(Kern, 1953).
Colostrum.
In the first few days after lambing the colostrum of the Awassi ewe is
characterized by a very high percentage of solids, more especially fat, protein
and ash, and a high degree of acidity. On the other hand, it is low in lactose
content. Becker (1958) has recorded an analysis of the colostral milk of Awassi
ewes, tested in 1943/44 (Table 4-52).
The milk flow
of the Awassi ewe. The Awassi ewe does not usually yield all
her milk at one milking or at one milking followed by stripping, as is common
in dairy cattle and goats. In the course of the machine or hand milking
process, the milk flow in the Awassi ewe pauses after about two-thirds of the
total amount of milk has been milked. Gall (1975) has pointed out that in
machine-milked ewes, the milk often flows in two
peaks. Previously it was common practice to remove the teat cups after the
first peak, thus allowing time for the alveolar milk to be ejected, and then to
put on the teat cups a second time. This procedure results in high labour
requirements. Milking routines have now been developed whereby the second
application of the cups is suppressed. To restart the flow and initiate the
second phase of milking, the udder has to be massaged by hand for about a
quarter of a minute while the cups are still on.
|
Days after lambing |
Total
solids |
Fat |
Total
protein (%) |
Casein |
Lactose
(%) |
Ash |
Acidity
(Soxhlet-Henkel degrees) |
|
Immediately |
35.8 |
13.0 |
18.5 |
13.5 |
2.9 |
1.40 |
26.0 |
|
1 |
24.6 |
9.2 |
11.0 |
8.7 |
3.2 |
1.06 |
14.2 |
|
2 |
21.3 |
9.0 |
8.0 |
5.3 |
3.1 |
1.01 |
9.4 |
|
3 |
19.5 |
7.7 |
7.9 |
5.0 |
3.0 |
0.84 |
8.1 |
|
4 |
18.4 |
7.2 |
6.6 |
4.8 |
3.5 |
0.95 |
7.0 |
|
5 |
18.0 |
6.7 |
5.9 |
4.9 |
4.4 |
0.92 |
6.9 |
|
6 |
17.9 |
6.9 |
5.9 |
4.3 |
4.2 |
0.93 |
6.5 |
|
7 |
18.5 |
7.3 |
5.7 |
4.4 |
4.5 |
0.95 |
7.1 |
|
8 |
18.1 |
6.5 |
5.9 |
4.0 |
4.6 |
0.93 |
6.0 |
|
9 |
18.4 |
6.9 |
5.6 |
3.4 |
4.7 |
0.90 |
7.2 |
|
30 |
18.2 |
6.9 |
5.4 |
4.1 |
4.7 |
0.95 |
8.7 |
For the purpose of obtaining the maximum amount of milk secreted in the
period elapsed since the previous milking, it is essential to milk the ewes
twice, both by machine and hand in a short interval. The secondary milking does
not consist of mere stripping, as in the case of cows and goats, but comprises
both milking and stripping.
During the
interval between morning and evening or night and noon milkings, there is a
gradual rise in udder pressure with a continued secretion and discharge of milk
from the cells into the lumina of the alveoli, the ducts and storage spaces of
the duct system, and the gland cistern. Owing to the increasing milk pressure
on the blood capillaries, which reduces the flow of blood, and to the growing
difficulty encountered in discharging the milk content of the cells into the
lumen, the cycles of secretion and discharge begin to slow down. After milking,
when the pressure is low, the epithelial cells of the alveoli rupture the
membrane and discharge their contents. With increasing milk pressure, the cell
wall can no longer rupture and the milk is discharged from the cell only as far
as it can pass through the semi-permeable cell membrane. The fat suspended in
the milk fluid cannot leave the cell and accumulates within it. The milk
discharged at this stage is low in fat and, to a lesser extent, in casein, but
is normal in sugar and albumin (Turner, 1952). After the primary milking of the
ewe, when the milk pressure is released, the cells of the alveoli burst and
discharge the accumulated fat globules which descend with the remaining fluid
from the lumina of the alveoli into the duct system and are recoverable at the
secondary milking and stripping.
Becker (1958)
attributes the necessity of the secondary milking to the structure of the udder
of the Awassi ewe, which does not permit collection of the major portion of the
milk in the cistern and larger ducts. A considerable amount of milk remains in
the narrow upper ductules and lumina of the alveoli and is only slowly forced
down the duct system after this has been emptied during the primary milking.
But this is only one reason for the necessity of the secondary milking. The
major factor involved in the slow inflow of the milk into the cistern and
larger ducts is doubtless the great viscosity of the ewe's milk owing to the
high percentage of solids.
Primary and secondary milking:
milk yields. The proportions of the primary to the secondary milk yields of
Awassi ewes vary considerably, as they depend on many factors, such as
individuality and age of the ewes, position of the teats, machine or hand
milking, the skill of the milkers, efficiency of the milking machine, suckling
or non-suckling of lambs, the stage of the lactation period, and total milk
production. In six tests of night and noon milkings in four different flocks,
the secondary milk yield ranged from 20 to 53.7 percent of the primary yield.
The total primary yield recorded was 282.5 kg and the secondary milk 95 kg on
average, a ratio of approximately 3:1 (Becker, 1958).
In a test with 154
Awassi ewes of an average age of nearly five years conducted in the mornings
and evenings of three consecutive days in March and April for the purpose of
recording the quantities of primary and secondary milk (Table 4-53), the ewes
were divided into five groups of similar size and composition, save for one
group which included suckling ewes, while the others were already in the second
half of their lactation period (see also Tables 4-55 to 4-57 and Table 4-82)
(Sharav, 1959).
In a test with six
hand-milked non-suckling ewes, beginning on the fourth day after lambing and
lasting for seven weeks, Edelman (1963) recorded average yields of 33.09 kg of
primary and 7.68 kg of secondary milk ,or 81.2andl8.8
percent, respectively, of the total yield. Seven non-suckling ewes of
| |||||||||||||||||||||||||||||
TABLE 4-54. Mean yields of secondary milk in relation to
the setting on of the teats | ||||
|
Secondary milk yields (g) |
50-100 |
100-130 |
140-170 |
above
175 |
|
Low set-on teats |
||||
|
Number of ewes |
26 |
27 |
17 |
14 |
|
% of ewes |
67 |
61 |
57 |
52 |
|
High set-on teats |
||||
|
Number of ewes |
13 |
17 |
13 |
13 |
|
% of ewes |
33 |
39 |
43 |
48 |
|
Total |
||||
|
Number of ewes |
39 |
44 |
30 |
27 |
|
%of ewes |
100 |
100 |
100 |
100 |
another flock produced — during a
15-day preliminary period and three 20-day test periods commencing after
weaning of their lambs at eight weeks of age—56.59 kg of machine-milked primary
and 7.93 kg of hand-milked secondary milk on average, or 87.7 and 12.3 percent,
respectively, of the total yields.
During the first
lactation, when the young ewes have not yet become fully used to being milked,
the average quantity of secondary milk is larger than during the second and
third lactations, namely 211 g as
against 144 g for each
milking. In later years there is a further decline in secondary milk yields to
121-129 g, with an average of 125 g for
each milking (Sharav, 1959).
Sharav (1959),
classing 140 ewes according to their mean yields of secondary milk into four
groups, namely 50-100 g, 110-130 g, 140-170 g, and 175 g and above, found no correlation between
the quantities of secondary milk and either height at rump, depth of udder,
superior udder girth, udder girth at height of teat bases, posterior and
anterior udder lengths, or length and diameter of teats, all measurements being
taken before as well as after milking. Only a single morphological feature,
namely the height of the setting on of the teats, shows a clear correlation
with secondary milk yields (Table 4-54).
In conformity with
these results, Eyal, Volcani and Sharav (1958) found in a test milking of 160
ewes that on completion of machine milking more milk remained in the udders
with high-set-on teats than in those with either oblique or vertical teats set
on low, namely 142 g as
against 125 g on average. A
similar result was obtained in a milking trial conducted by Jatsch and Sagi
(1979) in an experimental flock in northern Israel during nine months of
lactation. The yields from morning and afternoon milkings, separated into
machine milking, machine stripping and hand stripping fractions, showed that
ewes with teats obliquely projecting from the bottom of the udder yielded to
the machine milking fraction 57 percent of their total yield in the morning and
36 percent in the afternoon, while those with teats located far up on the sides
of the udder yielded only 43 percent of the morning and 21 percent of the
afternoon milk to the machine milking.
An increase or
decrease in total milk yield is not paralleled by its two components, primary
and secondary milk. In a trial conducted with 136 Awassi ewes with different
total yields, Sharav (1959) found that the general direction of either an
increase or a reduction in total yield was reflected in both phases of the
milking process, but that the quantity of primary milk followed the trend of
total yield much more closely than did the quantity of secondary milk (Table
4-55).
The question as to
whether, after machine milking, secondary hand milking and stripping in the
Awassi may or may not be dispensed with has been examined by Sharav (1971) in
two similar tests: one with two groups of 46 and 58 five-year-old non-suckling
Awassi ewes four months after lambing, and the other with two groups of 73 ewes
each, which were, however, nearer the end of the lactation period than were the
ewes of the first test. During three periods of 20 days each, with intervals of
a week between them, the ewes were alternately machine milked, followed by
secondary hand milking and stripping, or were only machine milked. The daily
milk yields for each ewe were recorded during the three 20-day periods of the
tests (Table 4-56).
The mean
difference in daily milk yields for each ewe between single machine milking and
machine plus hand milking and stripping for all animals included in these tests
was 35.9 g in favour of
machine plus secondary hand milking. In low-yielding ewes, that is, those
yielding below the average of the test groups, it was 59.7 g, and in
high-yielding ones, yielding above the average, 13.8 g. The difference is
statistically highly significant in ewes with relatively low yields, but not
significant in those with high yields.
The trials,
performed with non-suckling ewes at advanced stages of lactation, were supplemented
by another test with two groups of 65 four and a half- to five-year-old
suckling ewes each, comprising animals similar in age, lambing dates and
previous-year average milk yields (Sharav, 1971). Each group was tested by the
simple switchback method during two 20-day periods with a preparatory period
and interval of ten days each, one test period solely with machine milking
alternating with the second test period with machine plus secondary hand
milking, or vice versa. The lambs were separated from the ewes 24 hours before
the test milking. (See Table 4-57.)
Sharav (1971)
noted that the average daily loss of milk owing to the omission of secondary
hand milking was 173 g for
each ewe, 196 g for those
with yields above the mean and 155 g
for ewes with milk yields below the mean. Other than in the previous
test with non-suckling ewes, the rate of loss was statistically highly
significant for both groups. A large part of the milk lost by the omission of
secondary milking was recovered by the residue-suckling lambs (see p. 168 and
Tables 4-69 and 4-70).
The quantities of
milk yielded at the different phases of the primary machine and secondary hand
milking have been recorded in 24 four-year-old non-suckling ewes during two
periods of a fortnight each, with an interval of one week (Table 4-58). Support
of the udder by hand or mechanical means during machine milking changes the
ratio of primary to secondary milk yields in favour of the former.
In an experiment
with ewes having udders with an ill-defined differentiation between the halves,
Sagi and Morag (1974) found that insertion of the hand between the two glands
changed the angle of teat attachment from a high horizontal to a lower oblique
position and increased the percentage of
TABLE 4-56. Mean daily milk yields of non-suckling ewes
in three test periods of machine versus machine plus hand milking (g) | ||||||
|
20-day test period |
Group
I |
Group
II |
||||
|
Machine-milked |
Hand-milked |
Total |
Machine-milked |
Hand-milked |
Total |
|
|
Test I |
|
|
|
|
|
|
|
First |
1 114 |
— |
1 114 |
987 |
299 |
1 286 |
|
Second |
540 |
261 |
801 |
877 |
— |
877 |
|
Third |
607 |
— |
607 |
526 |
218 |
744 |
|
Test II |
|
|
|
|
|
|
|
First |
914 |
— |
914 |
804 |
256 |
1 060 |
|
Second |
508 |
192 |
700 |
720 |
— |
720 |
|
Third |
560 |
— |
560 |
411 |
155 |
566 |
TABLE 4-57. Average daily milk yields of suckling ewes
during two test periods of machine versus machine plus hand milking (g) | ||||||
|
20-day test period |
Group I |
Group II |
||||
|
Machine-milked |
Hand-milked |
Total |
Machine-milked |
Hand-milked |
Total |
|
|
First |
1 516 |
— |
1 516 |
1 391 |
284 |
1 675 |
|
Second |
1 157 |
224 |
1 381 |
1 138 |
— |
1 138 |
TABLE 4-58.
Average daily milk yields of Awassi ewes at different phases of primary
machine and secondary hand milking | ||||
|
Phase |
First
period |
Second
period |
||
|
Milk |
Milk |
|||
|
g |
% |
g |
% |
|
|
Machine milking until pause in flow |
888 |
56 |
792 |
53 |
|
Machine milking after udder massage |
444 |
28 |
438 |
29 |
|
Secondary hand milking and stripping |
256 |
16 |
274 |
18 |
|
Total |
1 588 |
100 |
1 504 |
100 |
primary
milk from 50 to 69 of the total yield in the morning after a previous interval
of 16 hours, and from 34 to 64 in the afternoon after an eight-hour interval
between milkings. Conversely, hand support of the udder reduced the secondary
yield obtained by machine milking from 35 to 19 percent of the total yield in
the morning, and from 50 to 23 percent in the afternoon. While these changes
were found to be highly significant, slight differences in the quantities of
milk obtained from subsequent hand stripping were not significant.
In another
experiment with two groups of high-milking dairy ewes, distinguished by
different udder conformations (see Fig. 4-3), Sagi (1978) recorded the daily
yields with or without mechanical udder support during milking (Table 4-59).
TABLE 4-59. Average daily milk yields according to udder
type and milking with or without mechanical udder support (%) | |||
|
Udder type |
Primary
machine milking |
Secondary
machine milking |
Hand
stripping |
|
I: Unsupported Supported |
44.0
61.0 |
43.2
26.0 |
12.8
13.0 |
|
II: Unsupported Supported |
60.3
71.0 |
29.3
17.7 |
10.4
11.3 |
Primary and secondary milking:
milk composition. The differences between the fat content of the milk
derived from successive primary and secondary hand milking are considerable, as
shown by two examples of the morning milk of 50 and 11 ewes (Table 4-60).
In five other
flocks the combined quantities and fat percentages from successive primary and
secondary morning and noon milkings were as given in Table 4-61.
| |||||||||||||||||||||||||||||
Eyal, Volcani and
Sharav (1958) recorded 6.23 percent fat in 195 samples of milk from primary
milkings and 9.03 percent in 424 samples from secondary milkings in
non-suckling ewes which, at the time of the test, yielded up to 400 g of milk for each milking. In 25
ewes, which still suckled their lambs at the time of the trial, the average fat
content in 568 g of
machine-milked primary milk for each milking was 4.05 percent, and in 162 g of hand-milked secondary milk,
7.54 percent.
In a test with two
groups of non-suckling ewes over seven weeks beginning on the fourth day after
lambing — one group with primary and secondary hand milking, and the other one
without secondary milking—the ewes of the latter group produced only 64.8
percent of the total quantity of fat yielded by those with primary and
secondary milkings. The fat percentages and relative quantities of milk at the
primary and secondary evening milkings of 15 ewes (seven of which suckled their
lambs during the night and eight in two residue sucklings) during the first
eight weeks of lactation are given in Table 4-62.
| ||||||||||||||||||||||||||||||||||||||||||
In the same flock,
non-suckling ewes whose lambs had been removed from their dams after the first
three days of life to be hand-fed produced 72.4 percent of the total amount of
fat at the primary milking and 27.6 percent at the secondary milking in the
first seven weeks of lactation. The average fat content in the primary milk was
7.04 percent and in the secondary milk 11.53 percent (Edelman, 1963).
In a test with
seven ewes, conducted in another flock over a period of 75 days after weaning of the lambs at the age of
eight weeks, Edelman ( 1963) recorded 8.18 percent fat
in the milk obtained in the primary milking and 14.86 percent in the milk from
the secondary milking, with an average of 8.87 percent in the combined primary
and secondary milk. The quantity of butterfat obtained at the secondary milking
and stripping was 19.1 percent of the total amount of butterfat.
The changes in the
fat content of primary and secondary milk coming to pass with the growing lapse
of time since lambing and the corresponding fall in the quantities of milk have
been examined in a trial with 150 ewes (Table 4-63).
The results of
this test show that while the percentage of fat in the primary milk rises with
the lapse of time since lambing and the decline in milk yields, the fat content
of the secondary milk is not affected by these factors to a parallel degree
but, on the contrary, shows a reduction.
In grouping ewes
according to different yields of secondary milk, the quantities of fat derived
from the primary milk show hardly any differences, whereas those of the
secondary milk vary greatly (Table 4-64) (Sharav, 1959).
TABLE 4-64. Variations in fat content of primary and
secondary milk with varying yields of secondary milk | ||||||||
|
No. of ewes |
Average milk yield per
secondary milking (g) |
Fat
content of secondary milk |
Fat
content of primary milk |
Fat
content of secondary milk (% of total fat) |
||||
|
No.
of tests |
% |
g |
No.
of tests |
% |
g |
|||
|
38 |
86 |
113 |
9.2 |
7.9 |
109 |
6.1 |
26.6 |
22.9 |
|
55 |
129 |
109 |
9.0 |
11.6 |
201 |
5.6 |
26.1 |
30.8 |
|
23 |
172 |
77 |
8.9 |
15.3 |
75 |
5.6 |
26.5 |
36.6 |
|
13 |
229 |
39 |
8.6 |
19.7 |
35 |
4.9 |
27.3 |
41.9 |
Both the fat and
solids-not-fat content of the primary milk depend on whether or not primary
machine or hand milking is followed by secondary hand milking. If the latter is
omitted, the milk is richer in fat and to some extent also in solids-not-fat
than is the primary milk of ewes which are successively milked twice. Table
4-65 gives the percentages of fat and solids-not-fat recorded in the sole or
primary and the secondary milk from two groups of ewes tested in three 20-day
periods of alternate machine milking and machine plus hand milking (Sharav,
1971) (see also p. 163 and Table 4-56). This test also showed that while the
fat content of primary milk is lower than that of secondary milk, the reverse
applies to the solids-not-fat percentage.
TABLE 4-65. Fat and solids-not-fat contents of Awassi milk
during three test periods of machine versus machine plus hand milking | |||||
|
Sole or primary milk 20-day test
period |
Fat
(%) |
Solids-not-fat
(%) |
|||
|
Group
1 |
Group
II |
Group |
Group
II |
||
|
First |
(–)
7.6 |
(+)
6.8 |
(–) 12.3 |
(+)
12.1 |
|
|
Second |
(+)
8.4 |
(–)
8.8 |
(+)
11.5 |
(–) 12.1 |
|
|
Third |
(–)
7.9 |
(+)
7.5 |
(–) 11-9 |
(+)
11.9 |
|
|
Average |
8.0 |
7.7 |
11.9 |
12.0 |
|
|
Secondary milk |
10.1 |
8.9 |
11.5 |
11.9 |
|
|
Note. |
Machine milking (+) with secondary
hand milking. |
||||
|
Machine milking (–) without secondary
hand milking. |
|||||
Sharav (1971) has
pointed out that with regard to the fat and solids-not-fat content of their
milk, ewes with yields below the mean display a stronger reaction to the
omission of secondary milking than those with yields above the mean. In the
former group, as a result of secondary hand milking, the primary milk contains
0.5 percent less fat and 0.4 percent less solids-not-fat than does the milk
obtained by machine without subsequent hand milking. The sole or primary milk
of ewes with yields above the mean does not show any such difference.
Effect of
secondary milking on persistency of milk yield. The influence
on the persistency of yields of secondary hand milking and stripping following
machine milking has been examined by Edelman (1963) by the double reversal
method in four groups totalling 30 ewes for 60 days after weaning of their
lambs at the age of eight weeks and a 15-day preparatory period. The experiment
showed that secondary milking had a favourable influence on the persistency of
milk yields which, during three periods of 20 days each, amounted to 76, 59 and
46 percent of the yield recorded in the preparatory period, as against 80, 55
and 41 percent in the ewes milked only once at a milking.
A second
investigation of the effect of secondary milking and stripping after primary
hand milking on the persistency of yields was conducted with two groups of six
ewes each whose lambs were hand-fed during a period of one preliminary week,
beginning on the fourth day after lambing, and six weeks of actual test. In
this test, secondary milking did not show a clear positive effect on
persistency, probably because of the small number of animals included in the
test (Table 4-66).
TABLE 4-66.
Milk yields during preliminary period (% of yield) | |||||||
|
Group |
Preliminary week |
Test
weeks |
|||||
|
1 |
2 |
3 |
4 |
5 |
6 |
||
|
Without secondary milking |
100 |
92.8 |
81.5 |
68.1 |
65.8 |
64.6 |
68.4 |
|
With secondary milking |
100 |
91.9 |
79.6 |
69.6 |
71.5 |
69.0 |
65.8 |
Retention of
milk by the Awassi ewe. Cows of primitive breeds frequently yield
their milk only in the presence of their calves. In improved dairy breeds it is
customary to strip the cows after machine or hand milking to obtain the
remainder of the milk not drawn at the main milking. The purpose of stripping
is to obtain a larger quantity of milk, more especially since the last-drawn
milk from a cow is particularly rich in butterfat, and to prevent a decrease in
milk secretion and premature involution of the udder owing to pressure within
the ducts and alveoli.
A similar
procedure has to be followed in the case of the Awassi ewe. However, in
contrast with dairy cattle, the Awassi ewe yields to stripping only part of the
milk remaining in the udder after machine or hand
milking. A remnant is retained even after thorough and repeated stripping, and
is recoverable only by the sucking lamb or the use of oxytocin. Apparently, the
stimulation of the Awassi ewe's teats by hand or mechanical milking causes
slighter afferent impulses to the central nervous system than suckling, with
the result that the oxytocin secreted by the posterior pituitary and supplied
by the blood to the mammary glands is insufficient to exercise optimum
intraglandular pressure to squeeze the last milk from the alveoli and ductules.
The quantity of
milk which Awassi ewes do not yield to the pail but retain in the udder for
their lambs was ascertained in fortnightly evening tests of 13 ewes in the
first two months of lactation (Folman, Eyal & Volcani, 1960). After primary
and secondary milking by experienced milkers, and as soon as no further milk
could be obtained by stripping, the lambs were admitted to the ewes and the
quantity of residual milk established by weighing the lambs immediately before
and after a few minutes' suckling (Table 4-67).
|
No.
of ewes tested |
Mean
quantity of milk yielded to the pail (kg) |
Mean
quantity of milk yielded to lambs (kg) |
Total
milk yield (kg) |
Milk
yielded to lambs (% of total yield) |
|
13 |
0.995
±0.184 |
0.570
±0.108 |
1.565
±0.180 |
36.5
±6.17 |
The high rate of
milk retention by the Awassi ewe is also illustrated by the fact that at the
first suckling immediately after milking the lambs on average obtained 39.3
percent of the total quantity of milk consumed by them during a 12-hour
suckling period, which, again, amounted to 55 percent of the total 24-hour milk
production of their dams. The ratio between the quantity of milk suckled by the
lambs in 12 hours and that yielded to the pail after 12 hours' separation from
their lambs ranged from 0.84:1 to 1.64:1, pointing to considerable individual
differences among Awassi ewes in milk withholding. This has been confirmed in
another test in which the differences between Awassi ewes in total lactation
yield were found to be much smaller than the differences in the quantities of
milk yielded at milking. Four ewes with total milk yields of 1 132, 1 115, 1
100 and 941 g, respectively, retained 128,0,233 and
533 g of these amounts for
their lambs. The average yields for each combined morning and evening milking
of all 25 ewes included in the test were as given in Table 4-68.
From these data it
appears that nearly all Awassi ewes retain some milk in their udders which is
not yielded to the milkers. This is connected with their maternal instinct.
Some ewes withhold only about 25 percent of the total quantity of milk
secreted, while others retain as much as 50 percent. Ewes retaining a small
percentage of their total milk are usually, though not always, among the
superior milkers. It is believed that at the morning milking the percentage of
residual milk in total production is somewhat smaller than at the evening
milking.
First-lambing ewes
retain a larger proportion of their total production for their lambs than older
ewes. In tests with 63 sucklings in 1952 and 250 in 1953, Doron (1954b)
recorded residual quantities of 27 and 26 percent, respectively, of the total
milk production of ewes that had lambed at least twice, while first-lambing
ewes retained 42.5 percent of their total production for their lambs, yielding
only
| |||||||||||||||||
TABLE 4-69. Residual daily milk yields after machine and
hand milking or machine milking only (g) | |||||||||
|
20-day test period |
Group |
Group
II |
|||||||
|
Machine
milked yield |
Hand
milked yield |
Residual
milk |
Machine
milked yield |
Hand
milked yield |
Residual
milk |
||||
|
First |
1 107 |
— |
261 |
863 |
294 |
188 |
|||
|
Second |
428 |
244 |
120 |
784 |
— |
273 |
|||
|
Third |
480 |
— |
195 |
426 |
201 |
125 |
|||
|
Average |
672 |
244 |
192 |
691 |
248 |
195 |
|||
TABLE 4-70. Residual milk consumption of lambs after
machine and hand milking or machine milking only of ewes (g) | ||||
|
20-day test period |
Group I |
Group II |
||
|
Machine
milking of ewes |
Machine
and hand milking of ewes |
Machine
milking of ewes |
Machine
and hand milking of ewes |
|
|
First |
— |
326 |
712 |
— |
|
Second |
450 |
— |
— |
522 |
|
Difference |
124 |
190 |
||
57.5 percent to the pail. The
quantities of residual milk consumed by the lambs varied greatly, namely
between 100 and 700 g a day.
The quantity of
residual milk depends to a considerable degree on the preceding milking system.
If it consists of primary machine milking followed by secondary hand milking
and stripping, the quantity is smaller than in case of machine milking only.
This is shown by the average daily quantities of residual milk for each ewe
obtained by Sharav (1971) by oxytocin injection immediately after completion of
machine milking or machine and hand milking in two similar groups of 16
non-suckling Awassi ewes each (Table 4-69).
In a test with one
group of eight and another one of ten suckling Awassi ewes, which in two 20-day
periods were alternately machine milked or machine and hand milked or vice
versa (see also p. 163 and Table 4-56), Sharav (1971) recorded the average
daily quantities of residual milk consumed by the single lambs given in Table
4-70. The test showed that the quantity of residual milk of ewes that were
machine milked without additional hand milking exceeded that available to the
suckling lambs after a secondary hand milking of their dams by an average of
157 g a day.
If lambs are
not suckled but hand- or self-fed, the residual milk remains in the udder. It
remains undecided whether this is available at the following milking (when a
similar quantity of residual milk is again retained) without detriment to the
milk secretion in the interval between two milkings or whether the residual
milk to some extent slows down milk secretion in the udder and thus lowers
total production.
While the large retention rate of milk in the
Awassi suggests the necessity for genetic selection against this phenomenon,
which is doubtless negative in a dairy breed, its high variability (as well as
its absence in the modern dairy breeds of cattle and goats) holds out promise
of success in this direction. The residual milk forms the
basis of the system of residue suckling, now generally employed by breeders of
the improved Awassi sheep of Israel.
Edelman (1963) recorded the average percentage and quantity
of butterfat in the milk which the suckling lamb obtains during the first eight
weeks of its life under the residue-suckling regime by allowing the lamb to
suck, after milking and stripping, the residual milk from one teat and by
simultaneously milking the other one to the last drops that can be obtained in
this manner. Eight lambs were weighed before and after residue suckling, and
the weight difference was compared with the weight of the milk obtained from
one teat. From the test of the residual milk the quantity of butterfat consumed
by the lambs was calculated for two residue sucklings over a period of eight
weeks. The result indicated that the average quantity of residual milk obtained
by the lamb during the test period was 24.64 kg with 8.66 percent or 1.960 kg
of fat.
However,
even with the hand milking of one teat while the lamb sucked the other one, a
small amount of milk still remained in the milked-udder half, which could not
be drawn by the milker but was yielded to the lamb. This minute quantity would
be even richer in fat than the residual milk actually recorded.
The
average percentage of fat in the residual milk (in addition to the primary and
secondary milk) of this residue-suckling group was compared with that of a
similar group of ewes, differing only in the suckling of their lambs 12 hours
at night. In the morning the ewes of this group were milked to remove any
leftover milk so that both groups started the day with empty udders (Table
4-71) (Edelman, 1963).
The
higher fat content of the milk in the residue suckling group than in the
12-hour suckling group is partly or wholly a result of the lower primary,
secondary and residual evening yields (345:383 g, 93:106 g, and 353:450 g,
respectively) as a consequence, apparently, of the lesser stimulation of
production by residue suckling than by 12-hour suckling.
The
milk of those ewes that yield the major part to the pail and retain little
residual milk for their lambs contains a higher percentage of fat than the milk
derived from ewes which at the primary and secondary milking yield a relatively
smaller portion of their total production (Eyal, Volcani & Sharav 1958).
In
the residual milk obtained by oxytocin injection immediately after milking in
two groups of 16 ewes each, milked by machine alternately with or without
secondary hand milking, Sharav (1971) recorded 11.2 percent fat in both groups, and 11.8 and 12.3 percent solids-not-fat,
respectively.
Milk consumption by lambs under different suckling regimes.
Bedouin and fellahin leave the young lamb with its dam until weaning at the
age of approximately two months. During this time the ewes are not milked.
Under this suckling regime, lambs of unimproved Awassi stock consume
approximately 30-40 kg of milk (Mason, 1967, gives an estimate of 20 kg; see p.
141).
During
the early years of Awassi improvement, until about 1950, the same suckling
system was prevalent among Jewish breeders in Palestine, at any rate with
regard to female lambs and males selected as future breeding stock. The
majority of the male lambs were sold for slaughter at an early age.
With
the improvement in milk yields, the lambs under this suckling regime consumed
ever larger quantities of milk. Hence, breeders considered the feasibility of
restricting the suckling time. At the Acre Government Farm in a trial with
three groups of female lambs, of which one group — in addition to a ration of
concentrates, hay and green fodder—received the whole amount of their dams'
milk for 60 days, the second group for four weeks and the third group for two
weeks followed by night suckling until the age of 60 days, the lambs of the two
test groups with partial suckling were not retarded in their growth at weaning
(Atzmon & Doron, 1951). With full suckling for a fortnight and partial
suckling until the age of 60 days, the lambs consumed between 46 and 771 of milk.
During the suckling period, the daily milk consumption ranged from 1.0 to 1.41
f or each lamb, with very little weekly variation. In another trial conducted
at the Neve Ya'ar Experiment Farm, Awassi lambs that received a total quantity
of 55.651 of milk weighed 21.1 kg on average at weaning, while those that
consumed 79.861 weighed 22.3 kg at 60 days (Becker, 1958).
In
view of the unnecessarily high milk consumption by lambs under a two months'
full suckling regime, breeders began to restrict the suckling period. The lambs
then remained with their dams for a fortnight during which the ewes were not
milked. During the following six weeks the ewes were milked in the evening
after their return from pasture, while the lambs stayed with them for 12 hours
at night. In the morning the ewes were again milked for the remainder left over
by the lambs.
At the present
time several different suckling regimes are current among breeders of the
improved Awassi. In a highly improved stud flock the male and female lambs stay
with their dams for one week. During this time the ewes are milked twice a day
as the lambs are incapable of consuming all the
milk produced by the ewes. After the first week a 12-hour suckling period
follows until the lambs are a month old and have attained a live weight of
11-12 kg. From then on they are suckled for eight hours a day, divided into two
periods of four hours each or of three and five hours, respectively. When their
weight reaches 20 kg, they are put on a four-hour suckling regime, divided into
two equal periods after morning and evening milking until they are weaned at a
weight of 30-45 kg. During the whole suckling period the lambs of this flock
consume 100-150 kg of milk.
Other
flock-masters keep the lambs with the ewes for, only three days after lambing
so that the lamb may enjoy the full allowance of the colostrum and both lamb
and ewe get used to each other. Thereafter the lamb may be put either on a
12-hour suckling regime or on two daily residue sucklings of varying length
until the age of two months, and on one residue suckling in the third month, at
the end of which the lamb is weaned. In a few flocks the lambs are separated
from the ewes soon after birth and reared artificially on a milk substitute,
just as is done with calves of dairy breeds.
The quantities of
milk consumed by lambs under different suckling systems in improved Awassi
flocks vary considerably, as shown by several tests. The milk obtained by
single lambs in a dairy flock of improved Awassi sheep with medium milk yields
(254.2 kg on average annually) under a 12-hour suckling regime was recorded
once a week during a period of eight weeks (Folman, Eyal & Volcani, 1960)
(see Table 4-72). The lambs were separated from their dams during the day and
joined them at night after evening milking. During the nights of recording the
lambs were suckled three times : in the evening, at
midnight and at dawn. Each time the lambs were weighed before and after
suckling, the weight difference being regarded as the weight of the milk consumed.
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
TABLE 4-73. Milk consumption by lambs under different
suckling regimes in a high-producing Awassi dairy flock during 8 or 9 weeks
after lambing | |||||||
|
Suckling period
(weeks) |
Sex of lambs |
12-hour
suckling |
4-hour
suckling |
Two
residue sucklings |
|||
|
No.
of lambs |
Milk
(kg) |
No.
of lambs |
Milk
(kg) |
No.
of lambs |
Milk
(kg) |
||
|
1-8 |
Male |
— |
— |
8 |
58 |
11 |
50 |
|
Female |
— |
— |
16 |
52 |
13 |
50 |
|
|
1-9 |
Male |
4 |
101 |
6 |
53 |
8 |
51 |
|
Female |
8 |
111 |
6 |
50 |
4 |
48 |
|
The milk consumed
by the 13 lambs during eight weeks after birth amounted to 55 percent of the
total milk production of their dams during this period (Folman, Eyal & Volcani,
1966a). The extention of this experiment to 13 male and 15 female single lambs
gave the same result. The average quantity of milk suckled by the lambs of
either sex in the course of eight weeks was 78 kg.
In two further
trials, conducted not in a medium- but in a high-producing flock (350-380 kg of
milk annually for each ewe) for eight and nine weeks, respectively, Folman,
Eyal and Volcani (1966c) compared the milk consumption of male and female lambs
under three suckling regimes: 12 hours, 4 hours, and two residue sucklings a
day of 30 minutes each (Table 4-73). The experiments showed that under the
12-hour suckling regime, the lambs of the high-producing flock obtained
approximately one-third more milk from their dams in nine weeks than did
those of the medium-producing flock in eight weeks. The quantities of milk
obtained by lambs in four hours of free suckling or at two residue sucklings a
day differed only slightly and statistically not significantly in favour of the
four-hour suckling.
The milk consumed
by the 12 lambs in nine weeks of 12-hour suckling a day amounted to 57 percent
of the total yield of the ewes during these weeks, that consumed by 12 lambs in
four hours of free suckling to 29 percent, and by 12 lambs under the regime of
two residue sucklings to 28 percent of the total yields of their dams over nine
weeks.
The 24 lambs under
the four-hour suckling regime during eight weeks obtained 37 percent of their
dams' total yield and the 24 lambs under the regime of two residue sucklings 34
percent of the total milk production of the ewes during this period (Folman,
Eyal & Volcani, 1966a).
The quantities of
milk consumed by lambs of the high-producing flock at one or'two residue
sucklings a day (along with liberal rations of hay and concentrates) from the
ninth to the twelfth and from the thirteenth to the sixteenth week after
lambing were as given in Table 4-74.
The suckling
percentage, that is, the amount of milk consumed by lambs as a percentage of
their dams' total milk production during a given period, amounted on average to
16 percent in one residue suckling and to 30.5 percent in two residue sucklings
during weeks 9-12. During weeks 13-16, the sucking percentage was 13 percent in
one residue suckling, and 31 percent in two residue sucklings (Folman, Eyal
& Volcani, 1966a).
In another trial,
Edelman (1963) recorded the quantities of milk consumed by lambs under
different suckling regimes in a dairy flock. Group I, comprising eight single
lambs, obtained the residual milk of their dams for eight weeks twice a day
after milking and stripping. Four of these eight lambs (group Ia) continued one residue suckling a day for another 12
weeks, while the other four lambs (group Ib) were weaned at eight weeks. Group
II, composed of seven single lambs, stayed with their dams during eight weeks
for 12 hours at night, after they had been hand milked and stripped in the
evening. Thereafter, three of these seven lambs (group IIa) continued one
residue suckling a day for another 12 weeks, while the other four lambs (group
IIb) were weaned at eight weeks, that is, according to the same procedure as in
group I. Under these different suckling regimes the lambs obtained the average
quantities of milk given in Table 4-75.
During the first
eight weeks the lambs that stayed with their dams for 12 hours at night
received nearly three times as much milk (71.1 kg) as
the lambs on a regime of two residue sucklings a day (24.6 kg). On a regime of
one residue suckling a day in the following 12 weeks, the difference in milk consumption
between the two groups (22.9 and 27.4 kg) was not statistically significant.
In a mutton flock of improved Awassi sheep in which the ewes
were not milked but suckled their lambs until weaning at the age of 16 weeks,
Folman, Eyal and Volcani (1960) recorded the quantities
TABLE 4-75. Milk consumption by Awassi lambs on residue and
12-hour suckling regimes (kg/head) | |
|
Group |
I- Two residue sucklings a day for 8 weeks |
|
Ia- One residue suckling a day from
weeks 9-20 |
|
|
Ib - Weaned at 8 weeks |
|
|
Group |
II - 12-hournightsucklingfor8weeks |
|
IIa - same as Ia |
|
|
IIb - same as Ib |
|
|
Weeks |
Group
I |
Group
II |
||
|
a |
b |
a |
b |
|
|
1-4 |
16.06 |
16.64 |
35.91 |
43.66 |
|
5-8 |
9.50 |
7.07 |
27.03 |
35.60 |
|
1-8 |
25.56 |
23.71 |
62.94 |
79.26 |
|
9-12 |
10.60 |
— |
9.20 |
— |
|
13-16 |
7.10 |
— |
8.68 |
|
|
17-20 |
5.23 |
— |
9.55 |
|
|
9-20 |
22.93 |
|
27.43 |
— |
|
0-20 |
48.49 |
23.71 |
90.37 |
79.26 |
of milk consumed by single lambs. Until eight weeks the lambs stayed at home and had free access to hay and concentrates.
From the age of eight weeks they were pastured for eight hours a day without
their dams, and from 12 weeks together with their dams.
The milk consumed
by the lambs was recorded once a week save for the
fourth month when records were taken once a fortnight. During the days of
recording the lambs were suckled three times: in the evening after the return
of the ewes from pasture, at midnight, and at dawn before the ewes were taken
out to pasture. Each time the lambs were weighed before and after suckling, the
weight difference being regarded as the weight of the milk consumed (Table
4-76).
In another publication (Folman et al., 1966), the results of the test were contracted as shown in Table 4-77.
At the first
suckling after the return of the ewes from pasture the lambs on average
consumed 41 percent of the total quantity of milk suckled in the course of 24
hours, a percentage very close to that obtained at the residue suckling in the
dairy flock (39.3 percent) (see p. 167).
TABLE 4-76. Milk consumption of
lambs in an Awassi mutton flock during a suckling period of 16 weeks (kg/head) | ||||||||||
|
|
No.
of lambs |
Average
milk consumption a day |
Total
consumption |
|||||||
|
Weeks0-4 |
Weeks
5-8 |
Weeks
0-8 |
Weeks
6-12 |
Weeks
13-16 |
Weeks
0-16 |
Weeks
0-8 |
Weeks
0-16 |
|||
|
Male |
7 |
1.686 |
1.598 |
1.642 |
1.589 |
1.024 |
1.474 |
91.952 |
165.088 |
|
|
Female |
7 |
1.486 |
1.445 |
1.466 |
1.382 |
0.827 |
1.285 |
82.068 |
143.920 |
|
TABLE 4-77. Average milk consumption by lambs during 16
weeks of suckling | |
|
Weeks |
Milk
(kg) |
|
0-8 |
87
±3.7 |
|
9-12 |
42
±1.7 |
|
13-16 |
26
±1.5 |
|
Total |
155
±6.1 |
TABLE 4-78. Milk yields of Awassi ewes in Cyprus under
different suckling regimes (kg) | |||
|
Suckling period |
0 |
2 |
35 |
|
35-day yield |
63 |
65 |
80 |
|
150-day yield |
172 |
185 |
210 |
|
Total milk yield |
195 |
212 |
252 |
Source: Cyprus ARI, 1973 | |||
Effect of
suckling on persistency of milk yield. Suckling has a
positive effect on the milk yield of Awassi ewes. In an experiment with 33
Awassi ewes descended from improved Israeli stock, the effects of three weaning
regimes—immediately after birth, after two days and after 35 days — on 35-day,
150-day and total milk yields were recorded in Cyprus in 1971. The 35-day and
150-day yields of ewes suckling one lamb for 35 days were significantly higher
than those of the ewes on the zero or two-day suckling regimes, while the
differences between the latter two were not significant (Table 4-78).
After weaning of
the lamb at the age of eight weeks or earlier, the milk yield of Awassi ewes
tends to decrease abruptly. In ewes in which residue suckling is continued
after this date, the yield decreases at a slower rate. In a test in 1952 in
which the milk yields of ten ewes whose lambs were weaned at eight weeks were
compared with 11 others with continued residue suckling, it was found that
suckling had a favourable influence on milk yields until the thirteenth week
after lambing. In a similar test with two groups of 19 and nine ewes in 1953,
the advantageous effect of suckling continued throughout the length of
the lactation period. The combination of the two tests, with the average yields
during the fifth week set at 100, shows the percentages in milk yields given in
Table 4-79 in the course of 19 weeks of lactation (Doron, 1954a).
It is notable that
the separation of the Awassi lamb from its dam for merely 24 hours on the day
of milk recording in itself causes a sharp decline in production in the
following days, as shown by a statistically significant difference in yield two
days after recording from that five days prior to recording (Folman, Volcani
& Eyal, 1962).
TABLE 4-79. Effect on milk yields of weaning at 8
weeks versus continued residue suckling | ||
|
Weeks after lambing |
Milk
yields of ewes (% of 5th week's yields) |
|
|
Lambs
weaned at 8 weeks |
Continued
residue suckling |
|
|
5 |
100.0 |
100.0 |
|
7 |
98.1 |
89.0 |
|
9 |
66.4 |
81.1 |
|
11 |
58.9 |
66.8 |
|
13 |
52.3 |
61.3 |
|
15 |
45.6 |
55.9 |
|
17 |
36.5 |
45.9 |
|
19 |
32.9 |
36.6 |
Fresh milk and
butter. Owing to its high viscosity and peculiar taste,
Awassi milk is not usually consumed as fresh milk. It can be used as such,
though, by mixing it at a ratio of 60 parts of milk with 40 parts of water,
when it approximates cow milk in composition and cannot easily be distinguished
from cow milk in taste. A more preferable means of fitting it for fresh milk
consumption is an admixture of 50-60 percent skimmed cow milk. This produces a superior drinking milk if not adulterated by water and a
better taste and flavour than an admixture of skimmed Awassi milk.
Butter made from
clean, sweet Awassi cream, separated and pasteurized soon after milking and
ripened with a clean-flavoured starter prepared from a pure culture of lactic
acid bacteria, is very similar in taste and flavour to butter made from cow
milk. Its consistency may be less firm, the colour a little paler and the
keeping quality poorer. Before centrifugation the milk has to be heated to
about 45°C, as otherwise an undue percentage of fat remains in the skimmed
milk. The butter must be carefully washed to remove remnants of buttermilk
which impair the keeping quality and flavour of the product, and subsequently
has to be salted.
In central dairies
in Israel, butter made from the milk of Awassi ewes is preserved for the
purpose of extending the season of cheese production beyond the main lactation
period of the ewes. During this time the milk from Friesian cows with the
addition of Awassi butter serves the production of cheese marketed as
Kashkaval, or a Provolone- or Roquefort-type cheese purported to be made of
sheep milk (Gordin, personal communication, 1982). The butter from Awassi milk
is necessary to convey the characteristic flavour and texture of sheep milk
cheese, characteristics which result from the partial lipolysis of the fat and
the difference between sheep and cow milk in the fatty acid composition, more
especially the higher contents of capryl, caprin, laurin and linoleic acids in sheep milk.
Sibdeh and
samneh or deehin. Bedouin and fellahin
produce samneh (clarified butterfat) from Awassi milk. Its production,
usually the work of women (sometimes with the help of an old man) involves two
stages: first, sibdeh, which resembles ordinary butter, is made. As soon
as milked, the fresh milk is poured into a goatskin bag which contains some of
the buttermilk that has remained from the previous day's churning. The skin is
hung outside the tent or building for the night. Early in the morning the bag,
half-filled with the sour and curdled milk, is blown up with air, hung from a
tripod and shaken for about one and a half hours until the butter separates
from the buttermilk. Toward the second stage, the sibdeh, which usually
contains larger or smaller amounts of dirt and buttermilk, is removed from the skin
bag and put into a copper vessel where it is salted and spiced with grain,
saffron or aromatic herbs. It is then heated over a fire under constant
stirring to a temperature of 100°C. In the course of this procedure the water
sinks to the bottom or evaporates, some of the dirt rises to the top where it
is removed with a wooden spoon, while the heavier dirt settles to the bottom.
After an hour or so the samneh thus derived is poured through a filtering cloth into a clean
vessel and left there for about a day. It is then put into a goatskin bag which
is kept in a cool place. Such a bag may contain up to 25 kg of samneh. Clean
samneh with a fat content that may reach 99.7 percent keeps well for a
fairly long time.
The large
quantities of buttermilk remaining from sibdeh production are either
consumed fresh or cooked with rice or converted into kishik (Hirsch, 1933).
In Iraq, deehin,
the local term for clarified butterfat (samneh or samnah) made
from Awassi milk, is made as follows (Williamson, 1949). As they are folded in
the evening the ewes are milked by the women. The milk is curdled and the cream
separated and churned in a skin. The butter is then removed and stored until a
sufficient quantity has been collected for clarification by boiling. During
this process the water evaporates and the curd solidifies so that it can be
removed from the fat, along with other solids separated by skimming. The deehin
is preserved in a skin for trading. Deehin dealers usually pack it,
without blending or further processing, in tins or sealed earthenware jars
where it may remain in a fair condition for at least a year. In northern Iraq,
where ambient temperatures are relatively low, it may not deteriorate for up to
two years. Ordinary Awassi ewes yield 1.0-1.5 kg of deehin for each lactation, and the superior Awassi type of northern
Iraq as much as 3 kg.
Lebben and
labneh (lebbeniya).
Considerable quantities of Awassi milk are used by the bedouin and
fellahin for the production of lebben and labneh. For the
preparation of lebben, fresh milk is boiled and then cooled to a
temperature of approximately 60°C. A little lebben of good taste from
the previous day, containing the micro-organisms necessary for fermentation, is
mixed with the milk. The mixture is kept for five to six hours at a temperature
of about 25°C when the firm lebben is ready for consumption.
Labneh (or labbeniya)
is prepared from milk that is boiled for a few minutes, cooled to 40-45°C,
inoculated with a starter of about 2 percent from a previous batch, and
stirred. Within two or three hours the temperature slowly drops to the ambient
temperature, the coagulum is kept in a cool place for 10-12 hours and is then
transferred to a goatskin or cloth bag that is hung up for about a week to
drain the whey. During this time the curd is repeatedly mixed by hand and salt
is added in daily portions. At the end of the week a semi-fluid, soft white
cheese is obtained which may be consumed fresh or, after keeping it in the sun
for partial drying, be formed into balls of about 3 cm in diameter and packed
into jars in which it is covered with olive oil. The product, which in Lebanon
is called labneh-ambaris, can be kept without refrigeration for up to a
year.
Labneh from
Lebanon, analysed by Baroudi and Collins (1976), had a titratable acidity of
1.05 percent, a pH of approximately 4.25, an
ethanol content of 1.25 percent, 4.2 ixg acetaldehyde,
and 34 u.g/ml acetoin plus deacetyl. In labneh from Israel, Rosenthal et al. (1980) ascertained 0.045 milliequivalents/g of free fatty acids and a pH of 3.59.
Five micro-organisms
were found to be responsible for the fermentation: Streptococcus
thermophilus, Lactobacillus acidophilus, Leuconostoc lactis, Kenyveromyces
fragilis and Saccharomyces cerevisiae. S. thermophilus and L.
acidophilus were responsible for the acid production, the former also for
that of the acetoin, and K. fragilis for most of the acetaldehyde
(Baroudi & Collins).
Kishik and chanklich.
To prepare kishik, buttermilk, to which salt has been added, is poured
into a cloth bag which is hung up for two or three days. During this time it is
repeatedly shaken until most of the fluid has drained off. The semi-dry
material is formed into round lumps of lemon-size which are dried in the sun
until they become very hard and may be kept unspoilt for a long time. Kishik
is used as an addition to many different dishes.
In Lebanon the
term kishik (kishk or kushuk) is used for labneh rubbed
with cracked wheat, and the term chanklich for labneh mixed with
herbs and spices, mainly thyme, shaped into balls and partially dried before
being packed into jars and covered with olive oil (Tamime & Robinson,
1978). This product is also known asjub-jub (Gordin, 1980).
Yoghurt.
In yoghurt prepared from Awassi milk by the primitive method common in
peasant households, two different bacteria are found, namely Streptococcus
thermophilus and Lactobacillus bulgaricus. In some samples Streptococcus
lacti also occurs; at a temperature of about 45°C, this produces
considerable quantities of lactic acid, such yoghurt having a very sour taste.
The activity of L. bulgaricus sets in when there is already a reduction
in the pH as a result of the
presence of lactic acid. The importance of this micro-organism lies in the
specific yoghurt flavour it produces. Yoghurt made in peasant households and
small dairies may contain additional micro-organisms that are typical of
different regions. Thus, in Turkey yeasts contribute to the alcohol content and
alcoholic taste of the local yoghurt. Some of the micro-organisms are found
only in fresh yoghurt, for part of them disappear
during storage when only those that can stand a pH of 3.7-4.1
remain.
If yoghurt is
prepared at the right temperature (above 40°C), the rapid development of lactic
acid also inhibits the growth of harmful non-thermophile micro-organisms. In
this way satisfactory yoghurt can be produced even from milk that has not been
pasteurized. But commonly the milk is heated to 90-95°C and stirred at this
temperature for up to two hours to destroy all micro-organisms contained in
fresh Awassi milk and to thicken it by evaporation. The milk is then cooled to
45-47°C and approximately 0.5 percent yoghurt is added from a previous batch.
The mixture is kept at a temperature of about 40°C for three to four hours
until it becomes firm. The curdled mass is poured into another vessel that has
been placed as low as possible so as to create a large amount of foam. The foam
forms a firm upper crust in which part of the dirt contained in hand-milked
Awassi milk accumulates and which isolates the yoghurt from the air. Before
consumption the foam is removed. The yoghurt is stored in a cool place, but
owing to the high total solids content of Awassi milk, the previous water
evaporation, and denaturation of whey proteins, Awassi yoghurt has a firm
consistency and the whey does not separate from it even if not stored in a cold
room.
In dairies the
Awassi milk is heated for five to ten minutes to a temperature of 90-95°C, then cooled to 40-42°C, and 1-2 percent of a pure culture
mixture of S. thermophilus and L. bulgaricus, preferably in a 1:1
ratio, are added (Kosikowski, 1978). The milk is usually poured into plastic
containers and kept at a temperature of 40°C. As soon as the yoghurt becomes
firm, it is transferred to a cold room.
Cheese
production from Awassi milk.
Baladi cheese. Fellahin also use Awassi milk
for the production of baladi cheese. A small piece of kid's or lamb's
abomasum is added to fresh, warm milk and the curdled mass put into a cloth bag
through which the whey drains. The residue is pressed, cut into small cubes and
salted for immediate consumption or preserved in brine.
Bedouin prepare
this cheese from Awassi milk in a similar manner. The milk is heated to the
near-boiling point, then cooled to about 40°C in
winter and 32°C in summer. After the addition of rennet the milk is kept in an
earthenware vessel at an ambient shade temperature for approximately three
hours. When whey appears on the surface, the curd is considered to be ready for
removal to a cloth bag which is suspended in or outside the tent for 12 hours.
The bag is then placed on a wooden board, another
board is put on top of it and pressed down by weights of approximately 1 kg for
each 1 kg of curd for 10-12 hours. The cheese is then removed from the bag and
cut into cubes. These are put in layers into a tin with about 10 percent salt
of the weight of the cheese spread between the layers. The salted cheese is
left undisturbed without any addition of water until enough moisture exudes to
cover it. For consumption, pieces of cheese are removed from the tin, warmed in
a pan over a fire until nearly melted, and eaten with home-made bread (Gordin,
personal communication, 1980).
Brynza.
The early development of the improved Awassi sheep in Palestine was closely
connected with the production of brynza cheese, on the sale of which the
economy of sheep farming in communal settlements and on private farms was
based. Brynza was prepared by the addition of 1 g of calf or lamb rennet extract and
sometimes also 30 g of
potassium nitrate (saltpetre) to every 7 or 8 kg of Awassi milk held at a
temperature of 32°C for 15 minutes to a half hour. The curd was cut into
pieces, removed in thin layers from the whey with a strainer, put into
cheesecloth and transferred to hoops or forms. Weights of V kg for every 1 kg of
milk were placed on the forms for half an hour. Then the pressure was doubled
for another eight hours, the cheese was turned over and the pressure reduced.
After a further 12 hours the cheese was cut into large pieces which were put
into a 12-percent salt solution. A few days later it was packed into large
tins, covered with a 14-percent solution of brine and kept in cold store until
sale. The taste could be improved by using boiled salted whey instead of water
for the brine.
For brynza to
be kept in brine the separated whey is heated to a temperature of 95°C and 15
percent sour whey is added to it. The mixture is kept at 95°C for another few
minutes, then cooled to 40°C, strained, combined with a starter and left for 48
hours. Then 20-22 kg of salt are added to every 100 1 of whey and the brynza
is placed in the brine for 24 hours. At the end of this period it is taken
out, salted and kept for four and a half days. The brynza is then packed
into barrels in layers with salt
on top of each layer. When the barrel is filled, the cheese is covered with a
14-percent salt solution of whey. With an eventual total salt concentration in
the whey of 17 percent, the brynza will contain 5-6 percent salt and
about 50 percent water. It can be kept at a temperature of 15°C for a short
time, and at 12°C for a longer period. The barrel has to be turned from time to
time to ensure an even distribution of the salt (Kern, 1953).
In large dairies brynza
is made from pasteurized Awassi milk to which are added 0.5-0.6 percent of a
good starter and a 40-percent calcium chloride solution in the proportion of 75
g for every 1001 of milk. A
quantity of rennet sufficient to cause curdling within 35-40 minutes is mixed
with the milk which is held at a temperature of 30°C in summer and 32°C in
winter. The curd is lifted with a flat spoon in layers of about 3-cm thickness
on a cheesecloth spread on a table so that the whey
may drain from it. Layers of curd are then put one on top of the other to a
height of 20 cm and the cheesecloth is tied up. After the whey has percolated,
the cloth is untied, the cheese turned over and the cloth tied up again. This
is repeated two or three times. The curd is then placed in a press. At first
only light pressure is exercized; after about 40 minutes the cheese is turned
over and the pressure is increased to approximately 15 kg for every 1 kg of
cheese. The finished product is placed in brine made from 26 kg of salt for
every 1001 of water at a temperature of about 18°C, where it remains for 24
hours. The brynza is then taken out of the brine, salted and packed in
barrels or boxes. In summer the brine is changed every seven days and in winter
every fortnight. It is not discarded but boiled and filtered, and its acidity
neutralized with lime.
Safed cheese.
This cheese resembles brynza, but the milk is thickened at a higher
temperature (33-35°C), which produces a firmer curd. The curd, separated from
the whey, is put into straw baskets which give the cheese a round shape and
leave a characteristic pattern on its surface. It is transferred several times
from basket to basket and salted each time. Safed cheese can be kept in
a cool place for several months if turned over and salted anew from time to
time. Its inside is softer than that of brynza and it contains a smaller
percentage of salt (Kern, 1953).
Feta. To
produce feta-type cheese (the name is derived from a Greek word) Awassi
milk, curdled with rennet or chicken pepsin in large vats, is cut into small
pieces of a gelatinous consistency. From the vats it is put into perforated
moulds in which it is left without pressure for 24 hours for the whey to
percolate. It is then cut into blocks of 1-kg weight, salted and placed in
layers in vessels with salt between the layers. After a week it is transferred
to canisters holding 16 kg of cheese and covered with salted water. The
canisters are then hermetically sealed and kept for a month in cold store at a
temperature of 6-8°C for the feta cheese to ripen.
Another procedure
for the production of feta cheese from ewe milk is recommended by
Kosikowski (1978). In summer the milk is kept for 10-15 minutes at a
temperature of 63°C or is pasteurized at this temperature for 30 minutes. It is
then transferred to cheese vats where it is cooled to 34°C in summer and 32°C
in winter. A 1-percent lactic acid starter is added and the milk is thoroughly
blended with rennet. After 30 minutes a firm curd forms in summer and after 60
minutes in winter. This will drop to the bottom of the vat in 10-55 minutes. It
is then scooped into a cloth bag that is hung in a cool room overnight for the
curd to drain and mat. Alternatively the curd may be transferred directly into
circular moulds, 40 cm in diameter, which are kept at room temperature for four
to five hours and frequently turned for the whey to percolate. The properly
knitted curd mass is cut into blocks of 10 cm. These are liberally salted on
the surfaces, kept on shelves for three to seven days at a temperature of
10-12°C, and turned daily until the salt content of the cheese is approximately
4 percent. At this point the feta cheese may be consumed fresh or the
salted curd blocks placed for curing in a beechwood barrel to a height of
two-thirds of the barrel, and the remaining space filled with saturated brine
containing 23 percent salt. In a week's time the cheese blocks are removed from
the barrel and washed with water or whey. They can then be preserved for three
to six months. Before dispatch to consumers, the excess salt is rinsed off in
cold water and the salt further reduced in barrels or pottery receptacles
filled with water or boiled Awassi milk containing 8 percent salt, where the
cheese acquires a creamy consistency and improved taste. The yield of feta cheese
from Awassi milk is 24-28 percent.
Provolone-type bashan cheese. An Italian Provolone-type cheese, sold
in Israel under the name of bashan, is
produced from Awassi milk that is curdled and cut into small pieces in a
similar manner to that of feta cheese. After separation of the whey, the
curd is deposited in round moulds which are placed in vessels filled with an
18-20 percent salt solution. After 24 hours it is removed from the moulds and
put separately into nylon nets in which the cheese is smoked. Instead of
smoking, large factories
use solutions with a smoky taste, in which the cheese obtains the
characteristic Provolone flavour. The nets with the cheese are suspended in
rooms of ambient temperature for a week. Thereafter the cheese is removed from
the nets and transferred to plastic bags in which it is vacuum-shrunk for six
to seven weeks before sale.
Roquefort-type Galilee
(Galil) cheese. Galil cheese is a local type of Roquefort cheese made in
Israel. To produce this cheese, Awassi milk is blended with rennet and
thickened at a temperature of 30°C for 80 minutes. The curd is cut into pieces
of approximately hazelnut-size and dipped in a Penicillium roqueforti mould. This is commonly
prepared from bread made of two-thirds wheat or rye flour and one-third barley
flour, which after piercing of the crust is kept at a temperature of 12°C and
85 percent humidity in a dark room. The mouldy bread is dried and pulverized (Spöttel, 1954). The curd treated
with the mould is transferred into hoops and held at a temperature of 22°C for
24 hours, when it is pierced by machinery with from 20-60 small needles to
facilitate the penetration of oxygen into the cheese and development of the
green-marbled appearance of the body of the cheese. The cheese is cured in a
store-room at 6-9°C and high humidity for three months. During this period it obtains
its characteristic taste and flavour from the mould and the change of part of
the milk fat into free fatty acids. For final ripening, it is transferred to a
cold store where it is kept at a temperature of 5°C for another three to six
months before marketing. Its water content is approximately 35 percent (Kern,
1953).
Kashkaval.
Kashkaval cheese from Awassi milk, in Turkey called kashar and in
Israel gilad, is made in round forms to a weight of 3-4 kg. After
coagulation of the milk by rennet, the curd is heated to 80-90°C for 30-40
minutes, kneaded, and very hot whey or water is poured on it. This causes
drainage of much of the water contained in the curd and the curd's dough-like
consistency. The curd is transferred into forms and subjected to pressure to
exclude any superfluous moisture so that the final product may contain little
more than 20 percent water. In the ripening room the cheese is salted daily on
both sides until a rind is formed that is impassable to salt. The cheese is
ready for marketing in about four to five months. If kept longer, it is apt to
deteriorate by the decomposition of fat and acquire a mouldy taste (Kern,
1953).
Composition of
Awassi whey. Whey derived from Awassi milk contains 6.7
percent solids on average. The monthly variation in the average composition of
whey is given in Table 4-80 (Kern, 1953).
Awassi whey can be used for the
production of a soft cheese in a proportion of 5-7 kg of cheese from 100 kg of
whey. Some dairies return or sell the whey to farmers for calf-feeding and what
remains is turned into dried whey powder.
Relation
between Awassi milk fat and cheese fat. Whey obtained in the
process of cheese production from Awassi milk contains variable quantities of
fat which can be separated. Generally, cheese made from milk containing less
than 3 percent fat retains practically all the fat, with hardly any of it going
into the whey. With increasing percentages of fat in the milk, progressively
more is discharged into the whey, as shown by the percentages of fat found in
the total solids of cheese made from Awassi milk (Table 4-81) (Kern, 1953).
|
TABLE 4-80. Monthly variation in
the composition of Awassi whey (%) |
||||
|
Month |
Total
solids |
Proteins |
Lactose |
Ash |
|
December |
6.92 |
1.25 |
4.85 |
0.82 |
|
January |
7.04 |
1.10 |
5.00 |
0.94 |
|
February |
6.66 |
1.03 |
4.70 |
0.88 |
|
March |
6.67 |
1.18 |
4.60 |
0.89 |
|
April |
6.77 |
1.19 |
4.82 |
0.90 |
|
May |
6.86 |
1.42 |
4.75 |
0.89 |
|
June |
6.64 |
1.30 |
4.37 |
0.93 |
|
July |
6.54 |
1.44 |
4.34 |
0.92 |
|
August |
6.06 |
1.55 |
3.56 |
0.99 |
|
September |
5.67 |
2.33 |
2.30 |
1.04 |
|
TABLE 4-81. Percentage of
fat in total solids of cheese made from Awassi milk containing variable
percentages of fat |
|
|
% of
fat in milk |
% of
fat in total cheese solids |
|
0.5 |
6.5 |
|
1.0 |
12.4 |
|
1.5 |
16.7 |
|
2.0 |
23.0 |
|
2.5 |
27.0 |
|
3.0 |
30.0 |
|
3.5 |
35.0 |
|
4.0 |
36.5 |
|
4.5 |
42.5 |
|
5.0 |
42.5 |
|
5.5 |
44.0 |
|
6.0 |
47.8 |
|
6.5 |
50.0 |
|
7.0 |
52.3 |
|
7.5 |
54.5 |
|
8.0 |
56.8 |
The bedouin milk their ewes in the
open. The animals are placed in two rows opposite each other and are tied
together in pairs by a long rope (see Fig. 4-4). This method was adopted by the
early Jewish breeders of the Awassi in Palestine and was in use, for example,
at Beyt Alfa and Kefar Gil 'adi. But at Tel Yosef, Aiyelet Hashahar and
Merhavia the ewes were tied individually with ropes to a long plank. As tying
the animals by ropes caused some deaths by strangling, breeders began to use a
straight-sided rack with upright movable iron slats to trap and hold the ewes
by the neck during milking (Figs 4-5 and 4-6) (Hirsch, 1933).
In the early
period of Awassi improvement, two milkers used to milk the same ewes alternately
for mutual control and efficiency of milking, one the primary and the other the
secondary milk and vice versa. In some flocks the ewes were milked not only
twice but three times in succession in order to obtain as much as possible of
the last rich milk.
Save for the first
days after lambing and the last weeks before drying up, Awassi dairy ewes are
generally milked twice a day, at night and noon or in the morning and evening.
In the winter, when the ewes are in the first months of their lactation and every
daylight hour is important for grazing, they are milked early in the morning
before going out to pasture and in the evening after their return to the shed.
From April, and throughout the hot and dry summer months, the cool early
morning hours are devoted to grazing and the flock returns for a long rest in
the shade of the shed at noon, being pastured again late in the afternoon when
the heat of the day has passed, until the onset of darkness. During this period
the ewes are milked either between 03.00 and 04.00 h and again at 13.00-14.00 h, or at 23.00
and 11.00-12.00 h (Becker,
1958).
Breeders endeavour
to arrange equal intervals between the two milkings in order to obtain similar
quantities of milk and not to overburden the udder by too long an interval.
However, Nitsan and Volcani (1960) have noted that equal intervals between
milkings do not necessarily produce equal quantities of milk in the Awassi. The
quantity of milk obtained in the morning is usually larger than that of the
evening milk, the difference being statistically significant. This is not
supported by Sharav's (1959) findings in a test, during three consecutive days,
with 154 ewes divided into five groups of similar composition. In this test the
variations in yield between morning and evening milkings were variable,
generally small, and statistically not significant (Table 4-82).
It would appear
that with equal intervals between milkings fluctuations between morning and
evening yields result from different conditions of feeding, activities and
environment (including ambient temperature) during the day and night.
Figure 4-4.
Bedouin women milking Awassi ewes in the Jordanian
steppe. (Photograph courtesy of Dr Ilse Köhler-Rollefson)
In practice it is
not always possible to maintain an equal interval between two milkings, and the
lapse of time between two consecutive milkings may be 11 and 13 hours or even
ten and 14 hours.
The first milking
machine for sheep was imported into Israel from France in 1954. Later on, small
portable installations were developed for temporary use. In 1955, two carousels
or roundabouts for large flocks were erected in two communal settlements. The
carousel is a revolving platform usually operated by hand. On Israeli farms
various sizes are now in use, holding 60, 72, 80, 96, 120
and up to 240 ewes at a time. The most common system is for 72 ewes. The
platform is divided into four sections: one for machine milking, the second for
secondary hand milking and stripping, the third for release of the ewes after
completion of milking, and the fourth for the introduction of a new batch of
sheep.
|
TABLE 4-82. Mean yields of morning
and evening milk in Awassi ewes (g) |
|||
|
Group |
Morning |
Evening |
Total |
|
I |
662.7 |
692.0 |
1 354.7 |
|
II |
670.3 |
656.6 |
1 326.9 |
|
III |
701.0 |
783.3 |
1 484.3 |
|
IV |
559.4 |
537.0 |
1 096.4 |
|
V |
543.6 |
520.3 |
1 063.9 |
|
Mean |
627.4 |
637.8 |
1 265.2 |
In the 72-ewe
carousel the machine milking section holds 18 ewes which are milked in three
groups by six units, 96 cm apart, each unit milking
three ewes in succession. The milking pit is situated around one-quarter of the
circumference of the platform and has a length of 5.70 m. The milking is
carried out by a single worker in the pit who moves in the opposite direction
to the movement of the platform. A second worker, outside the pit, completes
the secondary hand milking and stripping, attends to the concentrate feeding
and replaces the sheep that have been milked with a new batch.
In the 120-ewe
carousel, 32 ewes are successively milked by 16 units. After completion of
their milking the carousel is moved forwards. In the larger type of
installation, two workers operating the milking machine and massaging the udders
and a third one doing the secondary hand milking and stripping can milk 300
ewes in two hours, an average time of 24 seconds a ewe.
In very large
flocks two discontinuous rotary parlours have been installed side by side,
separated from one another by a single milking pit serving both
platforms (Fig.
4-7). An improvement over this system is represented by a central pit which
shortens the distance over which the operator has to move from 5.70 to 3 m and facilitates cooperation
between the two milkers.
In another system
of discontinuous rotary parlours in Israel with platform room for approximately
250 ewes, the ewes are arranged in two circles, an inner and an outer one, each
of which is served by a separate milking pit and different workers, but having
a common, 60-cm-wide manger. (See Fig. 4-8.)
In
the discontinuous rotary parlour the ewes enter the stationary platform and
thrust their heads through the yokes into the feed troughs. When all yokes are
occupied they are closed and the platform is rotated to bring a batch of ewes
opposite the milking pit. Here the platform is stopped and the ewes are milked.
After completion of milking, the parlour is again rotated to bring yet another
group of ewes into the milking position and to move those that have been milked
on for stripping. The platform is then rotated once more, the yokes are opened
and the ewes released.
A more recently
developed continuous rotary parlour greatly reduces the time and labour of the
milking operation. The platform is divided into sections, each with a trough
for concentrates, facing the perimeter. The ewe enters an empty section of the
rotating parlour through a race and is there constrained by the neck by means
of a top rail and lateral plates. The operator in the centre of the parlour
massages the udder and applies the teat cups of the milking unit, suspended
under the platform, to each ewe as she passes. The vacuum and milk lines run to
swivel manifolds in the centre. On completion of milking, the teat cups are
removed and returned to their original position under the rotary platform where
they are drawn through a bath for cleaning and disinfection in preparation for
a new cycle. The top rail for the confinement of the ewe rises as it approaches
the exit, and the ewe departs from the platform. The partition plates with the
attached troughs pass beneath the exit and entrance ramps, the empty troughs
are filled automatically with new concentrates, and the partition plates and
troughs return to the platform to receive further ewes for milking
(Figs 4-9 to
4-14) (Morag et al., 1972).
In view of the high cost of rotary parlours and the considerable labour
involved in milking with portable installations, three different row types of
mechanized milking parlours have been introduced for smaller Awassi flocks:
single row, little row, and double little row.
Row pits are
installed for either 36, 48 or 72-80 ewes, and double
pits for 96 animals. On small
Figure 4-9. Milking units below
platform and upper vacuum and milk lines of
continuous rotary parlour
family
farms row pits for 36 ewes are in use. In larger flocks the 48-ewe unit is the
accepted system for new installations, or two parallel row pits are installed.
The row pit has
two covers which are either closed using a hand lever or operated by pneumatic
or electric mechanisms. While 24 ewes are machine milked in the open section,
another 24 sheep, after completion of secondary hand milking and stripping, are
replaced in the covered part by a new batch. The sheep enter and leave from two
sides of the platform.
The operation of
machine milking in the double-row system consists of the following actions:
1) Distribution
of concentrate rations, entry of ewes into the milking stalls, closing of neck
locks.
2) Grasping
of teat cups, opening of tap for the cluster cups, application of cups to
udder.
3) Udder
massage until removal of teat cups and, if necessitated by a high setting of
the teats and
low
position of the milk cisterns, lifting of the bottom of the udder by the
lifting device suspended by a string from the upper frame of the milking unit.
4) Milker
proceeds to next sheep and applies teat cups.
5) At
the end of the milking pit, transfer of the cups to the ewe on the opposite
side of the pit.
6) After
milking of all ewes on both sides of the pit, removal of teat cups and closing
of unit tap.
7) Release
of neck lock device, removal of milked sheep, distribution of concentrate feed
in troughs, introduction of another batch of ewes.
As compared with
the discontinuous rotary parlour, in which only one-quarter of the working
space is utilized at a time, the row system permits full use of the working
space (Figs 4-15 to 4-17). It is easy to increase the number of milking units
and the number of workers, and the space taken up by the installation is small.
While the
differences in the cost of investment between the various types of installation
are large, the differences in time required for milking are slight (Sharav, 1959 ; 1973b). This does not apply to the continuous rotary
parlour in which the milking operation takes far less time than in the row
system or the discontinuous rotary parlour.
Milk recording of Awassi sheep was
initiated in Palestine in 1930. The systematic control of flocks dates from
1937, when the annual meeting of the Sheep Breeders' Association adopted a
comprehensive control plan. The association had to decide if control should be
restricted to a relatively small number of flocks, which would allow employment
of official controllers, or if the number of milk-controlled flocks should be
as large as possible, even at the risk of certain inaccuracies. The latter
course was adopted. Originally it was decided that control be carried out twice
a week, but as this demanded an excessive amount of labour, the control was
finally limited to once a month.
The quantity of
milk consumed by the lamb during the suckling period was determined by
multiplication of the yield on the first day of control after weaning with the
number of days that had elapsed between lambing and weaning. At that time the
lambs still obtained the entire milk of the ewes during the suckling period.
However, the length of the latter differed between lambs reared for slaughter
and females and selected males destined for breeding. Slaughter lambs were
weaned earlier than breeding animals. In case of the death of a lamb during the
suckling period, the latter would be shorter, while ewes with stillborn lambs
were milked from the beginning. In most instances of weaning after more than 60
days the lactation curve was already on the downgrade from the point at which
the milk yield would normally have been recorded for the first time. In these
cases the estimate of the quantity of milk consumed by the lamb, from the daily
yield at the first milk control after weaning, was lower than in reality. For this
reason it was decided not to permit the first control to be carried out later
than 75 days after lambing.
This system of
milk control was in vogue during the period 1937/38-1953/54, that is, for 16
years. In the meantime the milk yields of the Awassi had increased considerably
and Atzmon and Doron (1951) demonstrated experimentally that there was little
difference in the mean weight increase between three groups of lambs that
received (1) the entire milk of their dams for eight weeks, (2) all the milk for
four weeks and half the milk for another four weeks, and (3) all the milk for
two weeks and half the milk for six weeks. Many breeders, therefore, adopted a
regime of restricted suckling.
Experiments conducted at the
Acre Government Farm in 1951/52 and 1952/53 confirmed that suckling Awassi
lambs obtained considerably larger quantities of milk than had hitherto been
assumed (see p. 167, last paragraph). The average quantity of milk consumed
during the suckling
period of
eight weeks was 125 kg, while the control figures did not exceed 85 kg, that
is, 40 kg or 32 percent less (Doron, 1954b). From this it could be deduced that
the factual lactation yields surpassed those registered in the flock book on
the basis of milk control. To correct this inaccuracy, a new system of milk
control was introduced in 1954/55, which was based on the separation of the
suckling lambs from their dams during 24 hours of control. This brought the
estimate of the quantity of milk consumed by the lamb nearer to reality and
provided a full record of the yield during the entire lactation period.
However, trials
for the purpose of testing the accuracy attained by the new system of assessing
the lactation yields of ewes, conducted in 1958/59 and 1959/60 (see Tables 4-67
and 4-69), showed that the estimates obtained by the new system, although
closer to reality than those received under the earlier system, still lacked
exactness owing to the quantity of milk not yielded to the pail but retained by
the ewe for her lamb during the 24 hours of separation. This residue, while exhibiting
a wide range of individual variability, caused the figures of recorded yield in
every instance to be lower than actual production. Folman, Volcani and Eyal
(1962) therefore proposed an improved system of assessment of yields based on a
number of factors, the essence of which was the addition of the recorded
lactation yield to the difference between birth and weaning weights of the lamb
multiplied by a milk conversion factor, the sum thus obtained to represent the
total annual production of the ewe for the purpose of registration. This
proposed system was put into trial practice in 1960/61, but at the following
annual meeting of the Sheep Breeders' Association it was rejected as
impracticable and contrary to the tenets of Awassi improvement which aim at the
elimination of milk retention by ewes.
In 1961/62, milk
control of the Awassi was brought back to the earlier system, subject to the
following rules. The control had to be supervised by the Sheep Breeders'
Association. It had to be carried out by the breeders themselves on the
fourteenth, fifteenth or sixteenth of each month, and never on any other date.
The recording had to be inspected by the district instructors for sheep
husbandry. In the small number of flocks selected for the production of Awassi
stud rams, milk control could not be carried out by the breeders themselves but
by officers appointed by the Sheep Breeders' Association. In milk-recorded
flocks all ewes had to be included in the recording. The annual period of
control had to begin on 1 October and end on 30 September. On the day of
control the ewes were to be maintained in the same conditions as on other days
of the month. The control milking had to begin and end exactly at the same
times at which the ewes were milked on other days. Feeding conditions on the
day of control were to be similar to those normally maintained. The control had
to comprise the total milk yield of the ewes in 24 hours. The lambs had to be
separated from the ewes after the last milking preceding the 24-hour control
period. The ewes had to commence at the time of separation and end on the
following day at normal suckling time. The quantity of milk had to be measured
by weight to an accuracy of 20 g. At the end of the month the total 24-hour
yield, consisting of the sum of the morning and evening milk, was multiplied by
the number of days of the respective month in order to assess the monthly
yield. The day following lambing was reckoned as the first day of lactation.
The first control was not to be carried out before the fourth day after
lambing; if, for example, a ewe had lambed on the thirteenth of a month, the
first control of her yield had to be postponed to the following month. In order
to verify the accuracy of the individual control weighings, the sum of the
latter was compared with the total weight of the milk yielded by the flock on
the day of control (Fái, 1972).
In 1972/73,
following the decisions of the Symposium on Milk Recording Practices for Sheep
and Goats in memoriam of Dr M. Finci, held in Israel in March 1972, the
international rules for milk recording adopted at the symposium replaced the
previous recording method in the improved Awassi flocks in Israel. These rules
set down that milk control is to be carried out by the breeders themselves, while
the supervision of it rests with the Ministry of Agriculture. The ewes of every
milk-controlled flock must be marked with two tattoo numbers, the number of the
ewe in the right ear and the number of her dam in the left ear. In addition to
these marks, ear tags may be used. The lambs should be tattooed not later than
at the age of two months with consecutive numbers, the first female lamb born
in a certain year or season carrying the number following that given to the
lamb last born at the previous lambing time. It is prohibited to give the lambs
numbers of ewes removed from the flock earlier. If for some reason a ewe or
female lamb cannot be identified by her ear tattoo, she shall be given a new
number as though she represents a recent addition to the flock. The first
recording in a lactation period shall be carried out not before the thirtieth
nor later than the sixtieth day after lambing, and every milk-yielding animal
of a milk-recorded flock, which has passed 30 days from lambing, must be
included in the recording.
The following
procedure shall be observed at the recording: On the preceding evening the
lambs may be suckled for one hour after milking. They are then separated from
their dams for 24 hours. The first
record weighing is carried out on the following morning and the second one in
the evening of the same day. Thereafter the lambs are admitted to the ewes for
suckling. During the lactation period the milk yield of every ewe has to be
recorded in this manner as long as her yield does not fall below 200 g or 0.2 1
a day. The milk may be measured either by weight or volume to an accuracy of 20
g or 0.02 1. If, for technical reasons, it is impossible to weigh the secondary
milk of every ewe separately, the secondary milk from all ewes of the flock shall
be weighed or measured collectively and proportionally added to the quantity of
primary milk of every individual ewe. On the day of recording, milking shall be
carried out in the same manner and at the same times as on other days. If a ewe
shows signs of udder disease, this shall be noted in the record. For purposes
of calculation, the last day of consecutive milking, on which the ewe was
milked at least once in 24 hours, shall be reckoned as the last day of the
lactation. A full lactation period comprises not less than 150 days (Fái, 1972).
The fat content of
the milk of Awassi ewes is not tested in Israel along with the recording of the
milk yield. It was only for a few years in the early 1950s that the milk of
ewes with lactation yields exceeding 370 kg (e.g. 612 ewes in 1950/51 and 498
in 1953/54), which had been selected from among 11 flocks for the production of
stud and flock rams, was tested for butterfat content (see p. 154, last
paragraph, and Table 4-37). The butterfat test was discontinued mainly because
of the labour involved and a lack of interest on the part of the breeders in
the fat content of the milk of individual ewes, which has since been
disregarded in the selection programme. Breeders now have to be content with
the monthly reports furnished by the central dairies on the fat percentage of
the milk delivered to them by various suppliers.
