Genetics of growth and reproductive performance of Kenya Boran cattle

Animal models were used to estimate genetic parameters and trends for growth and reproduction of Kenya Boran cattle. Sex, age of animal, parity and year-season effects affected birth weight (BW), weaning weight (WW), 12month weight (12W), 18month weight (18W) and 24month weight (24W). Herd-year-season of birth and calving, and age at birth and calving affected age at first calving (AFC), pooled calving interval (CI) and calving intervals (CI1), (CI2) and (CI3). Direct heritability (h2) from univariate analyses of growth were low to moderate. Maternal heritability for WW, 12W and 24W were low. Direct-maternal genetic correlations were negative. The h2 for reproductive traits were low. The h2 from multivariate analyses for growth were moderate. The genetic correlations (rg) between growth traits were positive. The rg between reproductive traits were negative. The h2 from random regression analysis ranged from 0.11 to 0.33. The rg were positive tending to unity but declined with increase in lag between age points similar to permanent environmental correlation. The rp was negative between extreme points and positive between intermediate and later points with spikes along the diagonal