China Supakorn and Winai Pralomkarn

pp. 165 - 172

Abstract

The research was conducted to evaluate the factors affecting on weaning weight (WW) and Kleiber ratio (KR) and to
estimate genetic parameters for two traits in goats. The fixed factors affecting both traits indicated that year-season of birth,
sex, birth type and regression of the Thai Native (TN), Boer (BO) and Saanen (SA) influenced on WW and KR (P<0.05). Males
in this population were heavier (P<0.05) than females. Weaning weights and KR of single kid were significantly higher (P<
0.05) than other birth rearing types. Bivariate analysis of three models (Model 1: without maternal genetic effect, Model 2:
with maternal genetic effect and σ_am
 = 0, and Model 3: with maternal genetic effect and σam
≠ 0) were used to estimate genetic
parameters for this research. Estimated direct heritabilities from all models were 0.26 to 0.38 for WW, and 0.22 to 0.35 for KR.
Estimated maternal heritabilities from Model 2 and 3 were 0.09 and 0.12 for WW and 0.08 and 0.11 for KR, respectively. The
direct genetic and phenotypic correlations between WW and KR were positive and moderate values. Maternal genetic correlations between them were positive and of low values. An antagonistic direct-maternal correlations from Model 3 within
traits and between traits indicated that offspring of does with superior maternal abilities probably may provide an inferior
direct genetic effect in the same trait and between traits. It was therefore possible to rapidly improve WW and KR in this
goat population through selection, while the adverse effects of direct-maternal correlation within and between traits should
be considered. The best fit model would be a model including maternal genetic effect without a direct-maternal genetic covariance.