The project
Materials and methods
General discussion
Bibliography
S.A. Osei, K. Effah-Baah and P. Karikari
The authors are members of the Animal Science Department, University of Science and Technology, Kumasi, Ghana. This study was supported by the International Atomic Energy Agency, Vienna, and the Government of the Netherlands under Research Contract No. 4825/NL.
Milk and dairy products provide one way of overcoming the chronic protein deficiency in the average Ghanaian's diet. Kwashiorkor, the name of the disease that afflicts protein-deficient children, is actually derived from a Ghanaian word. Unfortunately, like most other tropical countries, Ghana has no indigenous dairy breeds, and the indigenous N'Dama beef breed and West African shorthorn cattle are poor milk animals. The scarcity of foreign exchange for importing milk and dairy products led the Government of Ghana to establish the Amrahia Dairy Cattle Pilot Project near Accra in the coastal savannah climatic zone.
The area of this project is characterized by rainfall that is seasonal, low, erratic and poorly distributed (Otchere, 1976). The dry season, lasting from November to March, results in a severe reduction in both the quantity and quality of forage. The humid forest zone, on the other hand, has a well-distributed bi-modal rainfall pattern (average 1 500 mm per annum) which ensures the production of more adequate and high-quality herbage throughout the year (Asare, 1970). In spite of this advantage, previously little attention was paid to cattle production in this zone, largely because of the presence of the tsetse fly and trypanosomiasis.
In 1974, the University of Science and Technology (UST)/Canadian International Development Agency (CIDA) Dairy Cattle Project, also known as the Boadi Cattle Project, was established to demonstrate the feasibility of raising exotic dairy cattle in the humid forest zone, and to evolve appropriate management procedures for adoption by prospective dairy producers.
By and large, reproductive traits have been used to assess the success of livestock projects The study described in this article was undertaken to evaluate the reproductive performance of a herd of Canadian Holstein-Friesian cattle that were born and bred in the rain forest of Ghana's Ashanti region.
An analysis was made of the performance records over a six-year period (1980-1985) of 27 locally bred Holstein-Friesian cows, born between 1975-1982 (see Table 1). These cows were the offspring of a foundation stock of 35 heifers and five bulls which were imported from Canada in June 1974 under a UST/CIDA cooperation agreement. The history and initial management of these cattle were described in detail by Kabuga and Alhassan (1981), who also investigated their performance up to 1979. Fifteen of the original 35 heifers were alive in 1980, but their records are not included in this study.
Management practices (1980 onwards). Calves are housed individually in cubicles until weaning takes place at six months of age, after which the calves are grouped in units of two or four per pen. Most of the lactating cows are tethered to stanchions during the night and in the afternoon, although a few are kept in pens. All cattle are released to graze in fenced paddocks from 6.00 to 11.00 in the mornings and then returned to the barn in the afternoons. Night grazing was also practiced up to the end of 1981 (Kabuga, pers. comm.).
Milking is done by hand twice daily, at 5.30 and 16.30. Lactating cows receive concentrates before each milking at the rate of 1 kg of concentrate per 2.5 kg of milk produced. Pregnant animals are also given supplementary concentrates according to the stage of pregnancy. Up to the age of six months, calves are not grazed but fed solely on concentrates.
After the morning milking, the animals are released to graze pasture until 11.00 when, to avoid excessive exposure to the sun, they are returned to the barn. While in the barn, they are given freshly cut forage ad libitum. The predominant forages grazed or fed include elephant grass (Pennisetum purpureum), Guinea grass (Panicum maximum), gamba grass (Andropogon gayanus), giant star grass (Cynodonplectostychus) and centro (Centrosema pubescens).
Location, climate and vegetation. The dairy herd is located at Boadi, approximately 10 km from Kumasi, the second city of Ghana. The latitude of this area is 6°43'N and longitude 1°36'W, i.e. within the tropical rain forest belt. The climate is generally hot and humid and the temperature ranges from 18°C at night to more than 30°C during the day, with average daily temperatures of 24°C (Gyawu and Agyemang, 1977). Relative humidity varies: it is as high as 97 percent (6:00 GMT) during the wet season (April to November) and as low as 30 percent (15:00 GMT) during the dry harmattan (wind) season (December to March).
Annual mean rainfall is approximately 1 500 mm. However, up to 55 percent of the rains fall between April and July (major rains), 30 percent from September to November (minor rains) and the rest during the harmattan.
Parameters studied. Production parameters studied included age at first calving, calf birth weights, sex ratio at birth, calving interval and post-partum return to pregnancy. In addition, conception rates, gestation length, milk yield and calf growth and mortality rates were investigated. The effects of lactation and season of calving on some of these traits were also evaluated as were the effects of calf sex on birth weights.
Statistical analysis. The effects of lactations, season and sex on reproductive traits were analysed by means of the least squares analysis of variance; Chi square analysis was employed to test for significant differences between the calculated and theoretical secondary sex ratios.
Results and discussions
A summary of the mean performance of locally bred Holstein-Friesian cattle over the six-year period under study is presented in Table 2. The effects of lactation number, season and sex are shown in Tables 3, 4 and 5, respectively.
Age at first calving. For the 27 locally bred animals, a mean age at first calving was obtained of 34.4 months with a range of 30 to 36 months (see Table 2). This compares with 30.8 months obtained by Gyawu and Agyemang (1977) for the foundation stock imported in 1974. Comparable figures for Friesians in other tropical areas are 34.83 months in Iraq (Kassir, Juma and Al Jaff, 1969), 40 months in Sri Lanka (Mahadevan, 1956) and 40.4 months in Uganda, according to Trail and Marples (1968). Rickman in 1969 and Oldenbroek in 1974, according to Gyawu and Agyemang (1977), reported that the average age at first calving of Friesian cattle in Canada and the Netherlands was 27.7 and 25 months, respectively.
While the figure obtained in this study compares favourably with those from other tropical countries, it is clear that there is need for a concerted effort to reduce the age at first calving. Greater attention to improved nutrition and alleviating the adverse effects of high temperatures would be of help. Specific studies to evaluate the effects of shades and shelters are required.
Calf birth weights. A total of 75 births were recorded. Of these 12 were stillbirths, four were abortions and two calves were so small, less than 18 kg in body weight, that they were not included in the data. The mean calf weight for the remaining 57 carvings was 30.42 kg, with a coefficient of variation (cv) of 21.1 percent (see Table 2). This value is much lower than the 42 kg reported by Davis, Plum and Brost (1954) or the 40.8 kg by Diggins, Bundy and Christenson (1984) for Friesian calves in the United States. Similarly, Ridler, Broster and Foot (1963) have reported higher calf birth weights for Friesians in England. In general, the offspring of females in hot climates are lighter at birth than their counterparts in temperate climates (McDowell, 1972). While the factors leading to lighter birth weights are many and complex, it is clear that the weight of the dam plays a prominent role since it is the major factor dictating weights of-offspring. Dams of comparable age are usually lighter under tropical conditions than those under cool conditions. McDowell has suggested, in addition, that the tropical environment exerts some influence on physiological functions of the dam, including endocrine responses which may affect birth weights.
1. Birth year, age and number of cows used in the study
Année de naissance, âne et nombre de vaches utilisées pour l'étude
Años de nacimiento, edades y número de vacas utilizadas en el estudio
|
Birth year |
1975 |
1976 |
1977 |
1978 |
1979 |
1980 |
1981 |
1982 |
|
Number of cows |
2 |
3 |
4 |
6 |
4 |
3 |
3 |
2 |
|
Average age1 (months) |
122 |
109 |
101 |
81 |
65 |
60 |
42 |
32 |
1 Overall average age of cows = 75 months.
2. Average six-year performance of Holstein-Friesians in a hot, humid environment
Performances moyennes sur six ans des Holstein frisonnes en climat chaud et humide
Efecto del número de lactaciones sobre el rendimiento de la reproducción de vacunos Holstein frisones en un medio cálido y húmedo
|
Trait |
Number of observations |
Mean + SE1 |
Range |
Coefficient of variation (%) |
|
|
Age at first calving (months) |
27 |
34.14 ± 1.27 |
30-36 |
9.88 |
|
|
Calf birth weight (kg) |
57 |
30.42 ± 0.85 |
20-45 |
21.10 |
|
|
Secondary sex ratio (%) |
57 |
53.97: 46.03 |
- |
- |
|
|
Calving intervals (months) |
45 |
16.00 ± 2.25 |
9.27-24.8 |
30.73 |
|
|
Post-partum pregnancy (months) |
28 |
6.85 ± 1.40 |
|
|
|
|
Conception rates (%) |
39 |
|
|
|
|
|
1st service |
- |
41.0 |
|
- |
- |
|
2nd service |
- |
33.3 |
|
- |
- |
|
3rd service |
- |
17.9 |
|
- |
- |
|
4th service |
- |
7.7 |
|
- |
- |
|
305-day milk yield (kg) |
20 |
2 498.6 + 147.8 |
1 512.8-3602.7 |
26.45 |
|
|
Gestation length (days) |
30 |
278.4 ± 11.62 |
265-288 |
3.18 |
|
|
Calf mortality (0-12 months) |
57 |
17.8 |
|
|
- |
|
Calf growth rate (kg/day) |
|
|
|
|
|
|
0-3 months |
45 |
0.44 ± 0.015 |
0.17-0.72 |
22.5 |
|
|
3-6 months |
43 |
0.27 ± 0.022 |
0.06 ± 0.72 |
53.7 |
|
|
6-9 months |
42 |
0.23 ± 0.016 |
0.05 ± 0.44 |
44.8 |
|
1 SE = standard error of mean.
3. Effect of lactation number on reproductive performance of Holstein-Friesians in a hot, humid environment
Effet du nombre de lactations sur les performances de reproduction des Holstein frisonnes en climat chaud et humide
Efecto del número de lactaciones sobre el rendimiento de la reproducción de vacunos Holstein frisones en un medio cálido y húmedo
|
Parameter1
|
Lactation number |
||||
|
1 |
2 |
3 |
4-7 |
||
|
Calf birth weight (kg) |
30.0 ± 1.2 |
28.53 ± 1.66 |
31.1 ± 2.32 |
32.4 ± 1.76 |
|
|
|
(17)2 |
(15) |
(9) |
(16) |
|
|
Calving interval (months) |
14.77 ± 1.5 |
16.28 ± 3.45 |
17.12 ± 2.87 |
15.83 ± 3.00 |
|
|
|
(15) |
(10) |
(9) |
(11) |
|
|
305-day milk yield (kg) |
1 983.73 ± 166.32 |
2 781.42 ± 245.44 |
2 936.25 ± 222.72 |
2 885.03 ± 283.3 |
|
|
|
(8) |
(6) |
(2) |
(4) |
|
|
Conception (%) |
|
|
|
|
|
|
|
1 st service |
27.27 |
38.45 |
42.87 |
62.5 |
|
|
(3) |
(5) |
(3) |
(5) |
|
|
|
2nd service |
45.45 |
23.07 |
28.58 |
37.5 |
|
|
(5) |
(39) |
(2) |
(3) |
|
|
|
3rd service |
18.18 |
30.76 |
14.29 |
|
|
|
(2) |
(4) |
|
(1) |
|
|
|
4th service |
9.09 |
7.69 |
14.29 |
|
|
|
(1) |
(1) |
|
(1) |
|
|
Number of services |
2.27 ± 0.61 |
2.08 ± 0.32 |
2.0 ± 0.5 |
1.36 ± 0.1 |
|
1 Means plus standard deviation (±).
2 Figures in brackets indicate number of animals.
4. Effect of season on performance traits of Holstein-Friesians in a hot, humid environment
Effet de la saison sur certaines caractéristiques de production des Holstein frisonnes en climat chaud et humide
Efecto de la estación sobre algunas características del rendimiento de los vacunos Holstein frisones en un medio cálido y húmedo
|
Trait
|
|
Dry season (November-March) |
||
|
Mean ± SE1 |
Coefficient of variation (%) |
Mean ± SE |
Coefficient of variation (%) |
|
|
Birth weight (kg) |
30.13 ± 1.3 |
5.61 |
30.7 ± 1.06 |
3.65 |
|
|
(31)2 |
|
(26) |
|
|
Gestation length (days) |
278.58 ± 13.48 |
4.32 |
278.28 ± 11.5 |
2.28 |
|
|
(12) |
|
(18) |
|
|
Post-partum pregnancy (months) |
6.79 ± 1.2 |
85.66 |
6.93 ± 1.49 |
83.31 |
|
|
(17) |
|
(11) |
|
|
Mortality, 0-12 months (%) |
8.2 |
|
9.6 |
|
|
|
(57) |
|
(57) |
|
1 SE = standard error of mean.
2 Figures in brackets indicate the number of observations.
5. Effect of sex on calf birth weight
Effet du sexe sur le poids des veaux à la naissance
Efecto del sexo sobre el peso de los terneros al nacer
|
Sex of calf |
Number of observations |
Mean calf birth weight (kg) |
Coefficient of variation (%) |
|
Male |
30 |
30.8 ± 1.45 |
24.82 |
|
Female |
27 |
29.99 ± 1.23 |
22.23 |
The effects of lactation number (see Table 3), season of birth (see Table 4) and sex of calf (see Table 5) on calf birth weights were not significant (P<0.05). There was a slight reduction in birth weight during the second lactation, but thereafter birth weights tended to increase. Calves born in the rainy (wet) season, April-October, weighed on the average 30.13 kg (CV = 5.61 percent) compared with 30.77 kg (CV = 3.66 percent) for those born in the dry season, November to March. Male calves were only slightly heavier than their female counterparts (30.8 versus 30 kg, respectively). These observations corroborate the earlier report by Kabuga and Alhassan (1981). The non-significant effect of season on calf birth weights is interesting and indicates that, with improved management where nutritional stresses are reduced, as one would expect from an institutional herd, there need not be the zig-zag pattern of weight presented by McDowell (1972). In addition, in the humid forest zone of Ghana where there is a relatively abundant supply of feed throughout the year the dams are also relatively well-fed throughout the pregnancy.
Sex ratio. There were approximately 30 males to 27 females at birth; that is 52.63 male births (see Table 2), a finding that is not significantly different from the theoretical 50:50 ratio.
Calving intervals. A total of 45 observations were made for the calculation of calving interval. Two records for the first lactation, and five for the second lactation were rejected because the intervals were rather low (less than or equal to nine months, indicating a recording error). For lactations above the fourth, five animals did not give birth again either because they were slaughtered or because they did not become pregnant for other reasons.
The calculated mean calving interval (see Table 2) for the study herd was 16 months. Hernandez (1965) obtained a mean calving interval of 15.38 months for Friesians in Venezuela, while Kassir, Juma and Al Jaff (1969) recorded 15.6 months for Friesian cows in Iraq. In comparison, Touchberry (1967) has reported that Friesian cattle in the United States of America were characterized by a calving interval of only 13 months. Since the gestation period in this study averaged 9.15 months (see Table 2), the difference in calving interval results from a difference in the days open (service period).
Cattle in this study did not conceive until about seven months post-partum. Preliminary studies of the progesterone profiles of these animals (Osei, unpubl.), however, indicate that a good proportion of these cattle resume oestrous cyclicity as early as 30 days post-partum. Apparently, one reason for the delayed pregnancy is the fact that cows are exposed to the bulls for approximately five hours per day only, while they could actually be exposed for at least double that period (see section on management practices). Consequently, females entering their heat periods in the afternoon hours or during the night were not served by the bulls. In addition, heat periods were not accurately or clearly recorded in many cases and no heat expectancy charts were used as a guide in detecting the occurrence of oestrus. It is obvious that accurate records or the use of heat expectancy charts are indispensable under a management system where bulls are with the cows for only a limited period of the day.
Neither the lactation number nor the season of calving had any significant effect on calving intervals. However, calving intervals tended to increase with second and third lactations and to decrease thereafter (see Table 3).
Post-partum pregnancy. The Holstein-Friesian cows generally became pregnant at an average of 6.9 months after their preceding parturition (see Table 3) for reasons given above. Management needs to be improved particularly in the area of heat detection and recording, and in exposing the female animals to the males for a longer time than has been the practice hitherto.
Conception rates. Of the 39 animals served and recorded during the study period, 16 (almost 41 percent) became pregnant at first service, l 3 (33 percent) at second service, seven (17.9 percent) at third service and three (7.7 percent) after four or more services (see Table 2). Thus 74.3 percent became pregnant after two services and almost 92 percent after three. These figures are higher than those calculated by Gyawu and Agyemang (1977) for the foundation stock. It is not clear whether this signifies an increased adaptability of the locally bred Friesians.
The number of services per conception averaged 1.97 and improved with the age of cows (see Table 3). This is hard to explain since one normally expects fertility to deteriorate as animals increase in age, particularly when they exceed five years (Spalding, Everett and Foote, 1975).
Gestation length. Gestation length averaged 278.4 days wth a coefficient of variation of 3.18 percent (see Table 2) and was not significantly influenced by the season of calving (see Table 4). The gestation length falls within the accepted range of values for Friesian cattle.
Milk yield. Friesian cows bred in the forest zone of Ghana produced a 305-day milk yield of 2 498.6 kg (see Table 2). This compares with the 4 496.0 kg milk yield produced by the foundation stock (Gyawu and Agyemang, 1977). An outbreak of streptothricosis in the herd between 1980 and 1985 is -partly to blame for the low milk yield (Kabuga, pers. comm.). Payne (1951) reported an average 305-day lactation yield of 2 355.9 kg by Friesians bred in Fiji, 2 355.9 kg although his data also indicated that milk production increased year by year. In Iraq, Kassir, Juma and Al Jaff (1969) obtained 2 482.8 kg as the mean 305 day milk production. In Venezuela, a tropical country with a well-established dairy industry, Martinez, Catalina and Combellas (1982) have reported a mean milk yield (305-day lactation) by locally bred Friesians as high as 4 041 kg. A close look at the range of production figures (1 512.2 to 3 602.7 kg) indicates that there is potential for improving milk yield of locally bred Friesians in the forest zone of Ghana. Milk yield increased with the age of animals (see Table 3).
Growth rates. Growth rates for Friesian calves bred in the humid forest zone of Ghana averaged 0.44 kg per day from birth to three months, 0.27 kg per day from three to six months and 0.23 kg per day from six to nine months. On average, therefore, calves weighed only 116 kg at nine months of age. Using Touchberry's (1967) growth rate data for Friesian calves in the United States, such a weight would be attained in less than four months. The slow postnatal growth of calves under tropical conditions is well known. It seems clear, however, that growth rates in this study were adversely influenced by management practices. Calves were given milk up to four weeks of age and then concentrates based on corn and fish-meal. At four weeks, calves are not efficient ingesters of such feeds and this fact undoubtedly influences growth.
Calf mortality Mortality within 12 months after birth averaged 17.8 percent, only slightly better than the 19.7 percent reported by Payne (1951) for Friesian calves in Fiji. Wilkins (1986) cites work from Bolivia which shows that, in some cases, calf mortality within six months of life reached 100 percent even on a research station farm. The relatively low mortality in this study could largely be attributed to the effective control of the tsetse fly - the carrier of trypanosomes - at the Boadi Cattle Project.
This study, like others before it, Rendel (1972) for example, indicates that Friesian cattle can be bred and maintained in tropical environments, although performing less well than Friesians maintained in temperate climates. Obviously, a decision to import these exotic cattle must be based on economic or other considerations. The poorer performance of animals in the hot, humid tropics has generally been blamed on the hostile climate which, through its high environmental temperatures, affects nutrition and disease (McDowell, 1972). Unimproved tropical forages are generally low in nutritive value and cannot form the basis of a feeding regime for high milk production in a hot environment (Wilkins, 1986); a Friesian cow's milk production will thus be below its genetic potential. Nor, it must be added, can poor-quality forage support good growth, satisfactory conception rates or other reproductive parameters. Furthermore, high temperatures, characteristic of the tropics, adversely affect feed intake of forages already low in nutritive value as well as efficiency of feed utilization, thus leading to a further deterioration in fertility and yield as well as increased mortality. High relative humidity aggravates these effects and is also congenial to the growth and development of parasites and diseases. In spite of this, Martinez, Galina and Combellas (1982), working in Venezuela under conditions similar to those prevailing in the humid forest zone in Ghana, have asserted that acceptable reproductive efficiency and production levels can be obtained from Friesians under tropical conditions.
This study has revealed that many of the reproductive traits are characterized by wide ranges of values and high coefficients of variation: birth weight, calving interval, milk yield, growth rate and post-partum pregnancy. Such large coefficients of variation are indicative of opportunities for improvement in these traits. Since most reproductive traits have a low heritability, it is apparent that most progress can be achieved by paying attention to environmental factors, especially improving the nutritional value of forages and ameliorating the unfavourable effects of heat stress. Studies in these areas will be most welcome.
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