Genetic and phenotypic parameters for birth and weaning weights of purebred and crossbred Ndama and West African Shorthorn cattle

LIVESTOCK pRzEE%PN ELSEVIER

Livestock Production

Science 5 1 (1997) 165- 17 1

Genetic and phenotypic parameters for birth and weaning weights of purebred and crossbred Ndama and West African Shorthorn cattle B.K. Ahunu a, P.F. Arthur b,* , H.W.A. Kissiedu

’

a Department of Animal Science, Uniuers& of Ghana, Legon, Ghana b Agricultural Research Centre, NSWAgriculture, Trangie 2823, Australia ’ Agricultural Research Station, UniL~ersity of Ghana Kpong, Ghana Accepted

11 April 1997

Abstract Calf records for a 30 year period (19651995) on purebred and crossbred Ndama and West African Shorthorn (WASH) cattle and their crosses with Santa Gertrudis or Red Poll were analyzed to determine factors affecting birth and weaning weights and to estimate genetic parameters. Male calves weighed heavier (P < 0.05) at birth and at weaning. Similarly period (year grouping) significantly influenced birth and weaning weights of calves. Season of birth did not influence calf weight at birth but significantly affected calf weaning weights. Purebred calves were similar in weight at birth and at weaning. Santa Gertrudis crossbreds weighed heavier than Red Poll crossbreds at birth only but not at weaning. Generally the poor level of nutrition of the natural pasture did not permit improved weaning weights in calves which were heavier at birth Additive direct heritability estimates were 0.45 + 0.08 for birth weight and 038 k 0.18 for weaning weight. Moderate genetic correlation (0.48) between birth and weaning weights indicates that selection for one trait would lead to moderate positive correlated response in the other trait. Due to negative genetic correlation (-0.29 + 0.16) between direct and maternal effects for weaning weight, and moderate he&abilities for both traits, selection for both the direct and maternal components of preweaning traits is advised. 0 1997 Elsevier Science B.V. Keywords:

Beef cattle; Growth; Genetic parameters;

Crossbreeding;

Tropics

1. Introduction Increasing the efficiency of beef production systerns by genetic means rests primarily on two procedures: (1) Selection within breeds to enhance critical characters and (2) selection among and combination of breeds to produce individuals that better fit pro-

* Corresponding

author.

0301-6226/97/$17.00 0 1997 Elsevier Science B.V. All rights reserved PII SO301 -6226(97)00064-X

duction conditions and resources (Long, 1980). In general, indigenous African breeds have been subjetted to little artificial selection and designed breeding programmes (Cartwright and Blackbum, 1989), therefore most indigenous breeds are often referred to as unimproved. However, such breeds have some good adaptative traits in their environments. Crossbreeding as a tool for improving indigenous tropical cattle has been reviewed (Long, 1980; Herring et al., 1996). The breeds to use to achieve a particular

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Production Science 51 (1997) 165-l 71

production objective has however differed in different environments. Since 1964, crossbreeding of the local Ndama and West African Shorthorn (WASH) cattle has been practised at the University of Ghana Agricultural Research Station, Kpong (ARSK). Crossing has also included the use of Red Poll and Santa Gertrudis semen at some stages. Since the inception of the programme only two reports (Ngere and Cameron, 1972; Ahunu and Arthur, 1989) have been published and both utilized subsamples of the data to evaluate F, crossbreds. There has however not been any comprehensive analysis of the data either to obtain genetic parameters or to evaluate genetic progress in these populations, both of which are necessary for planning future breeding strategies. Genetic parameters are characteristic of the population and also dependent on the environment. These parameters are therefore needed for this breeding programme under the specific production environment to enable prediction of response to selection and to evaluate the genetic programme. The objective of this study was therefore to assess the influence of the age of dam, sex of calf, season and year of birth of the calf and genotype on preweaning growth, and to estimate genetic parameters for birth and weaning weight for Ndama, West African Shorthorn and their crosses.

2. Materials and methods

2.1. Environment

and animal management

Data used in this study were obtained from the breeding and production records of cattle at the University of Ghana Agricultural Research Station, Kpong (ARSK). The herd was started with the introduction of Ndama and WASH from another research station (Agricultural Research Station, Legon) in 1964 for the purpose of developing improved beef cattle through crossbreeding among indigenous cattle and with exotic cattle. Purebred and crossbred Ndama and WASH were produced by natural matings within and across the two breeds while their crosses with either Santa Gertrudis or Red Poll were produced by artificial insemination (AI). All natural matings were done in single sire groups with the bull remaining with the females for most of the year. Whenever

imported semen was available, bulls were withdrawn from the mating groups and the females artificially inseminated when they show oestrus, until the required number of females have been inseminated. Bulls were then put back with the non-cycling females. In 1975, the WASH purebred herd was discontinued for greater emphasis on using Ndama and Santa Gertrudis or Red Poll as the basis for the beef development programme. Crossbreds of WASH however remained in the herd for further development. Calving occurred all year round as no strict breeding season was enforced. Calves were weighed within 24 h of birth and thereafter were weighed at monthly intervals. Calves were identified at birth and branded later, close to weaning. Calves were weaned at about 8-9 months of age. Dams were not milked and calves remained with their dams till weaning with no creep feeding. Male calves were castrated after weaning. All animals were treated against ecto- and endoparasites and routine prophylaxis for trypanosomiasis and babesiosis was administered. The herd grazed on natural pasture all year round with no supplementary feeding. The vegetation of the research station is described as coastal Savannah type. The predominant grass species on pasture were Andropogon, Brachiaria and Hyperrhenia interspersed with tree species like Azadirachta indica, Leucena leucocephala, Glyricidia sp. and other shrubs. The major limiting factor to the cattle programme at the station seems to be the poor nutritive value of the natural pasture especially during the dry season when the grass is reduced to standing hay or burnt by bush fires. Average annual rainfall for the 30-year period (1965-1995) was 1147 mm with a bimodal distribution which allowed the data to be classified into three seasons as follows: (i> Major rains (AprilJuly) average rainfall: 551 mm; (ii) minor rains (August-November) average rainfall: 430 mm; and (iii) dry season (December-March) average rainfall: 166 mm.

2.2. Statistical

analyses

Data on animals born from 1965 to 1995 were used. The data were edited such that only animals with complete records on sire, dam and all fixed

B. K. Ahunu et al. /Livestock Production

effects were used. The number of animals in the final data set used in the analyses classified by breed and period of birth is presented in Table 1. The data were first analysed by least squares using SAS (1989) GLM procedure. The model used included the fixed effects of sex (male and female), period (1965- 1974, 1975-1984, and 1985-19951, season of birth (dry season, major rains and minor rains), parity (1, 2, 3, 4 and 5) and breed (11 breeds; see Table 1) and all possible two-way interactions. For weaning weight, the age of calf at weaning (mean of 270 days) was included in the model as a covariate. Parity and all two-way interactions were not significant (P > 0.05) for both traits and hence were removed from the final model. A second set of analyses was performed where the variance and covariance components were estimated using a derivative-free restricted maximum likelihood DFREML procedure (Meyer, 1993) operated using a front-end programme described by Swan (1994). All known pedigree information was included in the analyses to increase the accuracy of the estimation through additional relationships between animals. A summary of the pedigree structure and descriptive statistics of the two traits are presented in Table 2. A univariate animal model was used for each trait, fitting direct and maternal additive effects

Table 1 Number of animals with birth (B) and weaning classified by breed and period subclass

(W) records

Science

Table 2 Descriptive

51

(1997)

165-l

167

71

statistics of the data Birth weight

No. of records No. of animals” No. of sires No. of dams Progeny per sire Progeny per dam Mean (kg) Standard deviation Coefficient of variation (SC) a In the analysis,

including

1071 1374 26 223 41.2 4.8 16.9 3.5 20.5

Weaning weight 626 1374 24 174 26. I 3.6 99.5 28.6 28.7

parents without records.

and their genetic covariances as random effects in addition to the error term, Fixed effects used were those found significant (P < 0.05) in the least squares analysis. This model was found to be appropriate for weaning weight. For birth weight however, maternal additive variance was zero, hence it was removed from the model. The genetic covariance between the maternal and direct effects was also removed. To estimate genetic covariance and correlation between the two traits, a bivariate animal model was used. He&abilities, phenotypic and genetic correlations were calculated from the estimates of the variance and covariance components. Standard errors for the heritability were obtained from cubic approximations of Meyer (1993). Estimates of total heritability were calculated as defined by Willham (I 972).

Period 1965-1974 Breed” Ndama (Nd) Shorthorn (WASH) Nd x WASH WASH x Nd Red Poll (RP) X Nd RP x WASH Santa Gertrudis (SG)XNd SG x WASH Nd x (WASH x Nd) Nd x (RP x Nd) Nd x (SG X Nd) Total a Crosses are indicated

1975-1984

19851995

3. Results and discussion

50 59 19

334 15 3

283 7 1

252 0 2

41 0 0

3.1. Fixed effects

12

3

5

5

0

0

6 50 37 21

4 28 18 15

19 0 28 0 6 4 8

11 0 14 0 42 17 34

3 0 9 0

361

BWBWBW 63 82 28

0 2

0 2

19 0 29 0 7 11 12

302

199

435

11

by sire breed X dam breed.

334

4 7 66

The analysis did not show any significant parity of dam effects for both birth and weaning weights (Table 3). In some studies this effect is fitted as age of dam. The results of this study is in agreement with observations by Ahunu and Arthur (1989) in an earlier report and also with reports of Tawah et al. (1993). Fordyce et al. (1993) found that age of dam did not affect birth weight of F, and 3/4 cross calves, however late generation calves with mature dams were heavier at birth than calves of the same

168 Table 3 Least squares means weaning weight

B.K. Ahunu et al. /Livestock

and standard

SCX

Male Female

errors

for birth weight

Birth weight

Weaning weighta

Number kg *

Number kg *

543 528

17.7kO.2 17.2 +0.2

318 308

302 435 334

16.9+0.2 19.6+0.2 15.8 kO.2

199 361 66

Season of birth Dry season Major rains Minor rains

347 396 328

ns 17.4kO.2 17.4kO.2 17.5kO.2

225 203 198

95.lk2.1 90.5 f 2.0

116.4 f 2.2 98.8 + 2.2 83.lk3.7 **

** 649 97 33 17 36 50 80 21 12 28 48

and

**

**

Period 1965-1974 1975-1984 1985-1995

Breedb Ndama (Nd) shorthorn (WASH) Nd x WASH WASH x Nd Red Poll (RP) X Nd RP x WASH Santa Gertrudis (SG) X Nd SG x WASH Nd x (WASH X Nd) Ndx(RPxNd) Nd x (SG X Nd)

Production Science 51 (1997) 165-I 71

16.3 +O.l 374 16.1+0.3 66 16.6f0.5 20 16.9*0.7 8 18.4f0.5 26 17.7 f 0.5 28 18.5f0.3 55 23.0f0.7 15 15.6*0.8 9 16.4kO.6 8 16.3i0.4 17

‘Adjusted to a mean weaning age of 270 days. b Crosses are indicated by sire breed X dam breed. * ** , = significant at P < 0.05 and P < 0.01, ns = not significant (P > 0.05).

89.6k2.3 98.7 + 2.3 90.1 f 2.3 *t 90.5 f 1.6 94.6 f 3.3 77.1+5.4 91.6k8.0 88.6k4.5 89.6 f 4.7 100.1 k3.1 98.6&6.2 83.4k7.5 112.7 f 8.0 93.7k5.1

respectively.

crosses from young cows. In studies where cows have calved regularly each year within a limited calving season, the trend is for age of dam effects to increase from 2-year old dams to a peak in 5-8 year old dams and then decline thereafter (Wakhungu et al., 1991; Heamshaw et al., 1994). In the present study however, no strict regularity of calving was enforced and therefore the strain of calving regularly and its consequent effect on calf performance was minimized. Sex effects were significant (P < 0.05) for birth and weaning weights. At birth male calves weighed 0.05 kg (2.9%) heavier than female calves but at the time of weaning male calves weighed 4.6 kg (5.1%) heavier. As might be expected, sex differences in-

creased as growth rate increased indicating that male calves are more responsive to improvements in the environment (Hopkins, 1977). The levels of weight advantage of male calves recorded in this study are comparable to what can be estimated from the values of Tawah et al. (1993) in Gudali but lower compared with values estimated by Tuah and Danso (1985) for WASH and Ndama in the humid forest zone of Ghana where favourable rainfall regime allowed greater quantities of high quality forage to be produced throughout the year, thus improving the nutritional environment for greater expression of male calves’ responsiveness to improved environment. Period had significant influence on both birth and weaning weights indicating in general that weaning weights of calves have tended to be lower in recent years. During the years under study no management changes were made. The slight decline in liveweights may be due to the fact that semen importation for the AI had not been regular since the early 1980’s and hence the purebred Ndama and back crosses to Ndama had become the dominant genotypes in the herd while the heavier Santa Gertrudis crosses have thinned out of the herd. Part of the reason may also be due to the fact that no new Ndama blood has been introduced into the herd for a very long time now. It is therefore possible that there has been some inbreeding in the Ndama herd leading to a reduction in calf weights observed in recent years (Kissiedu, Personal communications). The total rainfall for the three periods were as follows: 1965-1974 (10 years), 12421 mm; 1975-1984 (10 years), 11296 mm; and 1985-1987 plus 1989-1995 (10 years), 10691 mm (no rainfall data was available for 1988). Rainfall on natural rangelands affects the quality and quantity of available pasture and hence cattle productivity. The rainfall data suggest a decline in rainfall over time and thus may have partly contributed in the decline in weaning weights across the periods. Season of birth effects were not significant for birth weight but highly significant for weaning weight. Calves born in the Major rains weighed significantly heavier at weaning than their counterparts from the Minor rains and the Dry season. The effect of season is mediated through the quality and quantity of forage available to calves and their dams and these effects are more marked where animals are not given supplementary feed. Under improved nutri-

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tion in the humid forest zone of Ghana, Osei and Effah-Baah (1989) reported non-significant effect of season on calf growth and similarly for Jersey crosses with WASH at the other research station, the Agricultural Research Station at Legon (Ahunu and Grieve, 1980) where supplementary feeding in the form of corn or sorghum silage was provided in the dry season. For preweaning performance therefore, the results of this study favour the breeding of cows for calving in the Major rains since most of the lactation period would coincide with the raining season (major and minor rains). Breed effects were highly significant for both birth weight and weaning weight. It should be noted however, that breed effects were partially confounded with period, as some breeds (especially WASH and its crosses) were not represented in some periods of the study (Table 1). Therefore, only general trends can be inferred from the results for breed effects. Differences between the purebreds were small for both traits. At birth however, the crossbreds tended to be heavier than the purebreds. The mean for all crossbreds was 17.7 kg while that for all purebreds was 16.2 kg. The higher birth weight of the crossbreds had however eroded by the time of Thus, both crossbreds and purebreds weaning. weighed similar, namely, 92.8 kg and 92.6 kg respectively. This is perhaps due to the fact that the potential growth of the crossbreds may have been Table 4 Variance-covariance

Variance-covariance

components

and estimates

3.2. Genetic parameters Variance-covariance and heritability estimates for birth and weaning weights are presented in Table 4. The estimates indicate that both traits are moderately heritable, Maternal heritability was lower than direct heritability for weaning weight, and was unimportant for birth weight. This indicates that, together with a moderate to high coefficient of variation, considerable opportunity exists for the improvement of the two traits by selection. These results are in general agreement with average of estimates from the reviews by Mohiuddin (1993) and Koots et al. (1994a).

(t standard error) for birth and weaning

weights

Birth weight

Weaning weight

3.1 _ _

198.1 161.2 - 150.6 309.4 524.1

estimates

Additive direct variance Additive maternal variance Direct maternal covariance Error variance Phenotypic variance Phenotypic correlationa Genetic correlation” Heritability

for heritability

impeded by the unimproved nutritional status of the animals grazing natural unsupplemmented pasture. The means of all exotic crossbreds (SG and RP) were 18.4 kg and 97.3 kg for birth weight and weaning weight respectively. These were higher than values of 16.4 and 84.0 kg for birth weight and weaning weight respectively for the crossbreds produced by indigenous breeding (Nd X WASH, WASH x Nd and Nd x (WASH x Nd)). Santa Gertrudis (SG) crossbreds tended to be heavier at birth (average of 19.3 kg) than their Red Poll (RP) counterparts (average of 17.5 kg), however the differences had disappeared by weaning (97.5 and 97.2 kg, respectively, for SG and RP crossbreds).

4.6 8.3 0.24 0.48

estimates

Direct heritability (hi ) Maternal heritability (hh) Direct-maternal genetic correlation Total heritabilityb

0.45 f 0.08 ( rAM)

a Between birth and weaning weights. b Total heritability (!k$) = hi + 1/2h&

_ 0.45

+ 3/2r AMh Ah M‘

0.38 i 0.18 0.32 & 0.15 -0.29 f 0.16 0.39

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Production Science 51 (1997) 165-l 71

The genetic correlation between direct and maternal effects was negative ( rAM = - 0.29 f 0.16) for weaning weight (Table 4). The estimate was similar to those summarized in the reviews by Mohiuddin (1993) and Koots et al. (1994b) but higher than the near zero estimates reported by Mackinnon et al. (1991) for zebu-crossed cattle in Australia, and lower than those reported by Tawah et al. (1993) for Gudali cattle in the Cameroon. Due to the negative rAM and the moderate maternal heritability for weaning weight (hL = 0.32 f 0.15), selection for both direct and maternal components of preweaning traits is advised (Trus and Wilton, 1988). A possible explanation for the negative r,, estimate, provided by Tawah et al. (1993), is the harsh tropical environment as was the case in this study. It was suggested that females which are genetically small as calves grow up to become small dams which are better able to meet the requirements for their maintenance and growth of their calves in the sub-optimal environment than females which are genetically big under similar conditions. Consequently calves of big dams tend to be smaller at weaning than those of small dams. This is likely a form of adaptation under harsh tropical environment. Phenotypic and additive direct genetic correlation coefficients between birth weight and weaning weight were 0.24 and 0.48, respectively. While the phenotypic correlation coefficient was slightly lower than those from other studies, the genetic correlation coefficient was similar to literature values. The unweighted and weighted means obtained from a review by Koots et al. (1994b), of all published studies on correlations between birth and weaning weights were 0.36 and 0.46 for phenotypic correlations and 0.47 and 0.55 for genetic correlations, respectively. The lower phenotypic correlation relative to genetic correlation is in agreement with the trend reported in the reviews by Woldehawariat et al. (1977) Mohiuddin (1993) and Koots et al. (1994b). The moderate genetic correlation between birth and weaning weights indicates that selection for one trait will result in a moderate positive correlated response in the other trait. Estimates of direct additive heritability (hi) for weaning weight (0.38 + 0.18) and maternal heritability (/z&) for weaning weight (0.32 + 0.15) were in agreement with results of Mackinnon et al. (1991)

and Tawah et al. (1993). However, estimate of hi for birth weight (0.45 f 0.08) was slightly higher than that obtained (0.39) by Tawah et al. (1993) for Gudali cattle in Cameroon but lower than was recorded (0.65) in Wakwa cattle. The high hi obtained for birth weight in Wakwa cattle was attributed to the composite nature of the breed. Total heritability (ht ) is a measure of the fraction of the selection differential that would be realized if selection was based on the phenotypic value of the offspring. The estimates obtained in this study were moderate for both birth and weaning weights. The moderate h% indicates that selection for either birth weight or weaning weight is expected to be effective in spite of the antagonistic association between direct and maternal effects for weaning weight (Barlow, 1978). However, if the correlation between direct and maternal effects were zero, a greater response to selection would be achieved (Baker, 1980).

4. Conclusion The significant differences between male and female calves for birth and weaning weights was expected but the level of male weight advantage was generally low. Significant effect of season of birth on calf weaning weights generally reflect the plane of nutrition available for the dam and calf by natural grazing during the preweaning stage. It is therefore important for sex of calf and season of birth to be corrected for in analysing preweaning calf data. Although crossbreeding increased birth weights in the crossbreds, weaning weights were not increased. This was probably in part due to the unimproved nutritional environment for the crossbreds and perhaps the ability of the smaller indigenous breeds to utilize the suboptimal production environment more effectively than their bigger exotic crossbreds. Genetic improvement of indigenous West African cattle has been attempted in the past by crossbreeding with exotic breeds of cattle with little or no emphasis placed on selection. The estimates of genetic parameters obtained in this study indicate that if genetic improvement through selection for birth and/or weaning weight of indigenous cattle and their crosses is desired, there is scope for genetic progress to be achieved.

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Production Science 51 (1997) 165-I 71

Acknowledgements We wish to thank the many people who have assisted in the conduct of this research, in particular, staff of the livestock section of the Agricultural Research Station, Kpong, Ghana. Permission granted by Dr. J.W. Oteng, Senior Research Officer-inCharge, to use the data in this study is gratefully appreciated. We gratefully appreciate skilled technical assistance provided by Dr. J. Archer and Mrs. K. Dibley of the Agricultural Research Centre, Trangie, Australia.

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