Estimates of Heritability and Correlation for Milk and Growth Traits in Zaraibi Goat

Abstract

Records from the El-Serw research station belonging to Animal ProductionResearch Institute were used to estimate the genetic parameters for the economically most important milk and growth traits in the Zaraibi goat breed. There were 99 and 110 half-sib families over the periods 1995-2003 and 1990-2003 for milk and growth traits, respectively. Milk traits were, milk yield during the first 90 days and the total yield and the length of lactation period. The weight was recorded at birth, 90, 180 and 365 days of age. Mixed model methodology based on a multi-trait animal model was used to estimate the genetic and phenotypic parameters. A repeatability model was used for milk traits. Heritability for milk yield was 0.27 (90 days) and 0.35 (total) with a genetic correlation of 0.89 between them. The lactation period had heritability 0.15 and it was naturally positively correlated with yield, especially with the total yield (0.80). Therefore a selection program on the earlier 90 days yield record would give the best annual genetic changes for milk traits. The heritability for weight traits varied between 0.12 and 0.33 with high (0.42-0.82) positive genetic correlations between them. The pre-weaning gain (from birth to 90 days) is a very useful tool for selection, as it has a satisfactory heritability (0.33), it is very highly correlated with the post-weaning gain (from weaning to 6 months) and it is available well before any selection decisions are made.