Genetic and phenotypic parameters and annual trends for milk production and fertility traits of the Sahiwal cattle in semi arid Kenya |
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| Authors: | E D Ilatsia T K Muasya W B Muhuyi A K Kahi |
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| Institution: | (1) Animal Breeding and Genetics Group, Department of Animal Sciences, Egerton University, Njoro, Kenya;(2) National Animal Husbandry Research Centre Naivasha, Kenya Agricultural Research Institute, Naivasha, Kenya;(3) Animal Breeding and Genetics Group, Department of Animal Sciences, Egerton University, P. O. Box 536, 20107 Njoro, Kenya |
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| Abstract: | Data comprising 7211 lactation records of 2894 cows were used to estimate genetic and phenotypic parameters for milk production
(lactation milk yield, LMY and lactation length, LL) and fertility (calving interval, CI; number of services per conception,
NSC and age at first calving, AFC) traits. Genetic, environmental and phenotypic trends were also estimated. Variance components
were estimated using univariate, bivariate and trivariate animal models on based restricted maximum likelihood procedures.
Univariate models were used for each trait, while bivariate models were used to estimate genetic and phenotypic correlations
between milk production and fertility traits and between LMY, LL, CI and NSC within each lactation. Trivariate models were
used in the analysis of LMY, LL, CI and NSC in the first three lactations. Heritability estimates from the univariate model
were 0.16, 0.07, 0.03, 0.04 and 0.01 for LMY, LL, CI, AFC and NSC, respectively. The heritability estimates from trivariate
analysis were higher for milk production traits than those from univariate analyses. Genetic correlations were high and undesirable
between milk production and fertility traits, while phenotypic correlations were correspondingly low. Genetic trends were
close to zero for all traits, while environmental and phenotypic trends fluctuated over the study period. |
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| Keywords: | Annual trends Parameter estimates Sahiwal cattle Selection Kenya |
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