| dc.description.abstract | 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. | en |
