An evaluation of a long-term breeding programme in a closed Sahiwal herd in Kenya: I. Effects of non-genetic factors on performance and genetic parameter estimates
Rege, J.E.O. | Lomole, M.A. | Wakhungu, J.W.
SUMMARY: Records covering the period 1964 through 1986 obtained from the Kenya Sahiwal Stud were used to estimate genetic parameters of reproductive and production traits. The average Sahiwal cow produced 1663 kg of milk in 305d every 426d and required 2.1 inseminations per conception in a highly variable (CV = 179%) insemination period of 50d, with first calving occurring about at 41 months. Calves weighed 23 kg on average at birth and attained 55 kg in 98d. Heritability estimates were generally low for reproductive traits, ranging from 0 to .15 except for age at first calving (.29) but were higher for production traits being .35 for first lactation milk yield, .27 for milk yield of combined lactations, .40 for birth weight, and .35 for age at 55 kg. Genetic correlations between milk yield and reproductive traits were negative (-.12 to -.29) but not significantly different from zero. Although genetic parameters indicated potential for genetic improvement of production traits, performance was generally lower than expected. Some parameter estimates were not consistent with those currently assumed in the breeding programme. It was concluded that there is need to examine genetic and environmental trends in performance and to estimate other parameters in order to develop a more efficient breeding programme.
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