Abstract
Résumé
Introduction
Materials and methods
Results
Discussion
References
R.M. Njwe and Y. Manjeli
Department of Animal Production, Institut National du Développement Rural
(INADER), University Centre of Dschang, B.P. 222, Dschang, Cameroon
Milk yield of Cameroon Dwarf Blackbelly sheep was estimated by the indirect method of weighing lambs before and after sucking during a period of 12 weeks. Twenty-two lactations were evaluated between February and December 1985.
Average daily milk yield ranged from 0.31 to 0.50 kg for ewes suckling single lambs. Maximum weekly milk yield (3.52 kg) was attained during the 4th week of lactation after which production declined. Differences in milk yield between ewes and weeks of lactation were highly significant (P<0.01). Milk yield per lactation was positively correlated with the age of the ewe at the beginning of lactation.
La méthode de la double pesée d'agneaux (avant et après la tétée) a été utilisée pour déterminer la production laitère de brebis Djallonké à ventre noir camerounaises. Vingt deux lactations de 12 semaines de durée ont été estimées entre février et décembre 1985.
La production journalière moyenne fut comprise entre 0, 31 et 0, 50 kg pour des brebis allaitant un seul agneau. La semaine de production maximale fut la 4e après la mise-bas (3, 52 kg); la production a ensuite décliné. La production laitière a varié de manière significative (P < 0, 01) d'une brebis à l'autre et d'une semaine de lactation à l'autre. La production totale par lactation est positivement corrélée avec l'âge des brebis au début de la lactation.
Sheep are generally not milked in Cameroon. However, it has been established that milk production has direct effect an weight gain by lambs. Barnicoat et al (1956) reported a positive correlation between growth rate of New Zealand Romney lambs (between 0 and 12 weeks) and fat content, and total milk consumption with correlation coefficients of 0.72 and 0.61, respectively. Milk production during lactation is an important factor affecting maternal ability in sheep. Estimates of milk production by Cameroon Dwarf Blackbelly sheep do not exist. The present study focused on estimating daily and total milk production during the lactation period of Cameroon Dwarf Blackbelly sheep; establishing the lactation curve; and investigating the relationship between age of animal at the commencement of lactation and total milk production during the lactation period of 12 weeks.
Animals
The sheep used for the study are popularly called Blackbelly sheep as a result of the distinct black abdomen and dominant brown colour on all other parts of the body. They are a strain of the West African Dwarf sheep found along the Atlantic coast from Senegal to Angola. This sheep is a hair type with a thin tail. It measures 55 to 65 cm at the withers. The head is small with a straight profile. The ears are small and droop a little. Males have short spiral horns. In general, females are hornless but sometimes they have spurs. The hair is short and quite smooth but is sometimes rough. Adult males weigh 25-35 kg while adult females weigh 20-25 kg. Birthweight ranges from 1.5 to 2.0 kg. Average age at first lambing is 534 days while the lambing interval is 228 days. The sex ratio is about 49 per cent male and 51 per cent female. Prolificity has been estimated at 107 per cent while fertility and fecundity rates are 113 and 121 per cent, respectively. This sheep is thought to be the ancestor of the Barbados Blackbelly sheep (Epstein, 1971). It is found in the forest region of Cameroon, Gabon, Congo and Zaire (FAO, 1979). Mason (unpublished data) reported that 10.5 per cent of sheep in the Central and South Provinces of Cameroon were the Blackbelly sheep.
The sheep had been collected from the East and South Provinces of Cameroon in 1980 and maintained at the University Farm at Nkolbisson near Yaounde until 1984 after which in December 1984 they were transferred to Dschang on the high plateau (with an altitude of 1450 metres, annual rainfall of 2200 mm and average temperature of 20-22°C).
Feeding of lactating sheep
The experimental period was between February and August 1985. Lactating sheep were fed cut fresh Pennisetum purpureum daily with concentrate supplement. The composition of the supplement is presented in Table 1. Enough forage was provided to each lactating ewe such that a residue of about 20 per cent was always left. animal received 200 grams of concentrate supplement which was served at 08.00 hours everyday.
Table 1. Composition of concentrate and Pennisetum purpureum fed to lactating Cameroon Blackbelly sheep.
|
|
Concentrate* |
Pennisetum purpureum** |
|
Dry matter |
88.05 |
25.60 |
|
Crude protein |
19.36 |
10.59 |
|
Crude fibre |
10.38 |
28.70 |
|
Ether extracts |
4.80 |
2.40 |
|
Nitrogen-free extracts |
54.87 |
49.96 |
|
Ash |
10.59 |
8.35 |
* 100 kg concentrate composed of 50 kg maize, 30 kg wheat bran, 18.5 kg soybean and 1 kg bicalcium phosphate and 0.5 kg salt.
** Mean composition of P. purpureum samples for entire experimental period.
Assessment of milk production
The assessment of milk production started after the first three days of lactation to enable lambs suckled colostrum. Lambs were kept separated from ewes and only brought together at periods of suckling. Milk production of the ewes was estimated by the indirect method of weighing lambs before and after suckling using a sensitive balance. Estimates were carried out on alternate days up to weaning at 12 weeks. During the first four weeks lambs were allowed to suckle at 2-hour intervals between 8 a.m. and 6 p.m. Between the 5th and 12th week of lactation, four suckings at 3-hour intervals between 8 a.m. and 5 p.m. were allowed. Milk production data collected for four days of the week were extrapolated for the week of seven days.
Weekly milk production was assessed for 22 ewes during lactation periods of 12 weeks. The data were subjected to analysis of variance using the randomised complete block design where week of lactation represents treatments and each ewe was a replicate. Total milk production of ewes was correlated with age to determine the relationship between them.
Weekly milk production by Cameroon Dwarf Blackbelly sheep are presented in Table 2. From parturition there was an increase of milk production from 2.95 kg per week to a peak of 3.52 kg at four weeks and thereafter a gradual decline to 2.10 kg at 12 weeks of lactation.
Table 2. Mean weekly milk production by Cameroon Blackbelly sheep.
|
Lactation week |
Total milk production (kg) |
Number of observations |
Average milk production (kg) |
|
1 |
64.91 |
22 |
2.95 |
|
2 |
73.67 |
22 |
3.35 |
|
3 |
76.95 |
22 |
3.50 |
|
4 |
77.46 |
22 |
3.52 |
|
5 |
70.68 |
22 |
3.21 |
|
6 |
65.07 |
22 |
2.96 |
|
7 |
64.44 |
22 |
2.93 |
|
8 |
62.97 |
22 |
2.86 |
|
9 |
58.31 |
22 |
2.65 |
|
10 |
55.42 |
22 |
2.52 |
|
11 |
48.89 |
22 |
2.22 |
|
12 |
46.25 |
22 |
2.10 |
Average milk production per lactating ewe is indicated in Table 3. Total milk production per lactation ranged from 28 to 42 kg, corresponding to 0.33 to 0. kg per day.
Age at the time of parturition (days) was positively correlated with total milk production (kg) and the correlation coefficient of 0.71 was significant (P<0.50). The regression equation describing the relationship was as follows:
Y=21.497+0.021x(r=0.71)
where
Y = milk production per lactation (kg)
X = age of ewe at parturition (days).
Table 3. Milk production by Cameroon Dwarf Blackbelly sheep during the first three months of lactation.
|
Animal number |
Age of animals (days) |
Total milk production (kg) |
Average daily production (kg) |
|
1 |
na |
27.79 |
0.33 |
|
2 |
na |
32.40 |
0.39 |
|
3 |
528 |
26.00 |
0.31 |
|
4 |
707 |
36.81 |
0.44 |
|
5 |
844 |
42.15 |
0.50 |
|
6 |
na |
34.03 |
0.41 |
|
7 |
na |
35.00 |
0.42 |
|
8 |
597 |
37.59 |
0.45 |
|
9 |
na |
37.06 |
0.44 |
|
10 |
na |
39.59 |
0.48 |
|
11 |
628 |
37.06 |
0.44 |
|
12 |
na |
39.59 |
0.48 |
|
13 |
na |
37.18 |
0.44 |
|
14 |
847 |
31.27 |
0.43 |
|
15 |
435 |
34.21 |
0.41 |
|
16 |
635 |
33.33 |
0.40 |
|
17 |
na |
34.21 |
0.41 |
|
18 |
na |
30.63 |
0.36 |
|
19 |
na |
31.47 |
0.37 |
|
20 |
na |
37.12 |
0.44 |
|
21 |
758 |
36.33 |
0.43 |
|
22 |
877 |
40.18 |
0.48 |
na = not available.
Maximum daily milk production was attained by the Cameroon Dwarf Blackbelly sheep at the 4th week for lactation. This implies a more gradual increase of milk production to attain a peak when compared to some breeds for sheep that do so more rapidly and earlier. Coombe et al (1960) reported that milk output reached a peak at 10-20 days; while Ricordeau and Denamur (1962) reported that Prealpes sheep attained milk production peak at 25 days.
The daily peak milk production of 0.50 kg obtained with Cameroon Dwarf Blackbelly sheep is low when compared to 1.25 litres per day with Prealpes sheep (Ricordeau and Denamur, 1962). Spedding (1963) has indicated that peak milk yield in sheep varies with breeds. Bonsma (1929) reported peak daily milk production in Merino sheep of 0.77 kg while Owen (1957) indicated a value of 2.23 kg.
The yield of 28-42 kg of milk by Cameroon Dwarf Blackbelly sheep during a lactation period of 96 days is low when compared to 48 and 53 kg by Ossimi and Rahmani sheep, respectively (Sharafeldin and Mostageer, 1961), for a lactation period of 84 days and 100-150 kg by Awassi sheep for a period of 160 days (Koseoglu and Aytug, 1961).
The positive relationship between age and milk production obtained in the present study with Blackbelly sheep agrees with reports by Gruer (1959) that total milk production per lactation by Precoce, Stara, Zagora and Plovdiv sheep increased upto six to seven years before declining. However, the oldest ewe used in the investigation of the age/lactation total milk relationship had not attained three years.
The evaluation of milk production needs to be extended to other local breeds for which we do not have any information at the moment.
Barnicoat C R. Murray P E, Robert E M and Wilson G S. 1956. Milk secretion studies with New Zealand Romney ewes. Part VIl. Experiments on early weaning of lambs. Journal of Agricultural Science 48 (Part 1):22-24.
Bonsma F N. 1929. Factors influencing the growth and development of lambs, with special reference to cross-breeding of Merino sheep for fat lamb production. University of Pretoria Agriculture 48. University of Pretoria, South Africa.
Coombe J B. Wardrop I D and Tribe D E. 1960. A study of milk production of the grazing ewe, with emphasis on the experimental technique employed. Journal of Agricultural Science 54:353.
Epstein H. 1971. The origin of the domestic animals of Africa. Volume 2. Africana Publishing Corporation, New York, USA.
FAO (Food and Agriculture Organization of the United Nations). 1979. FAO production year-book 1978. Volume 32. FAO, Rome, Italy. 287 pp.
Gruer V. 1959. Correlations between milk production, wool yield and body weight in sheep. Mez.Sel.hoz. z. 3(2):109- 118.
Koseoglu H and Aytug C N. 1961. Studies on the milk production of Awassi sheep which are breeding at Cukurova Stock Farm. Lalahan Zootek. Arast. Enst. Derg. 1 (10):100-110.
Owen J B. 1957. A study of the lactation and growth for hill sheep in their native environment and under lowland conditions. Journal of Agricultural Science 48:387-412.
Ricordeau G and Denamur R. 1962. Production laitier des brebis Prealpes du sud pendant les phases d'allaitement, de sevrage et de traite. Annales de Zootechnie 11 (1):5-38.
Sharafeldin M A and Mostageer A. 1961. Suckling in Ossimi and Rahmani lambs. Journal of Animal Production (U.A.R.) 1 15-59.
Spedding C RW. 1963. Sheep production and grazing management. Bailliere, Tindall and Cox, London, UK.
