Performance of Ayrshire-Sahiwal crossbred calves at the coast
Data from Mariakani Animal Production Research Sub- Centre, at the Coast Province of Kenya, was used to estimate genetic and environmental effects on birth weight, preweaning average daily gain, we~hing weight (at 5 months) and preweaning survival for 8 genotypes of crossbred and straightbred calves. These genotypes are: >87.5% (highgrade) Sahiwal, 75%Sahiwal 25%exotic, 67%Sahiwal 33%exotic, F1 Ayrshire Sahiwal, F1 Friesian Sahiwal, 67%exotic 33%Sahiwal, 75%exotic 25%Sahiwal and >87.5% (high-grade) exotic. A total of 1135 records were analysed for birth weight, 727 for rate of gain, 745 for weaning weight and 1156 for survival. A fixed effects least squares model was used for growth traits while a logistic model was employed in the analysis for calf survival. Genotype of sire was important for weight gain and weaning weight but not for birth weight. Friesian-sired calves gained more per day and weaned heaviest, followed by Ayrshire-sired calves and last were the Sahiwal-sired calves. Dam genotype was important for birth weight and weaning weight but not for preweaning weight gain. Crossbred dams generally performed better than the straightbred Sahiwal dams. Mean performance of crossbreds was also generally higher than that of the straightbred dams in all the traits studied. Maternal heterosis in F1 dams was, however, not important for in any of the growth traits. Genotype of calf was important for preweaning average daily gain, weaning weight and survival but not for birth weight. Friesian cross calves performed better than Ayrshire cross calves in most traits. Generally, crossbred calves performed better than straightbred calves. The level of heterosis in the F1 Ayrshire-Sahiwal calves was -2.1% for birth weight, 7.0% for rate of gain, 3.0% for weaning weight and -7.3% for preweaning survival. Additive genetic effects were found to be more important than heterotic effects and the calves with a higher proportion of exotic genes were generally favoured.