Meta-analysis of performance and genetic parameter estimates for growth and body weight traits of sheep in the tropics

Abstract

A meta-analysis on 68 articles was performed to combine the estimates of genetic parameters of growth traits in sheep from the tropics. 10 traits were included which met the quality control criteria. Weighted estimates were obtained by combining 275 means, 442 heritability estimates (255 direct, 98 maternal, and 62 common environmental), and 765 correlation estimates (381 phenotypic and 384 genetic). A random-effects model was used and the heterogeneity of parameter estimates was evaluated using the I2-statistic. Direct heritability increased with age from 0.196 at birth to 0.388 at 18-months of age while maternal and common environmental effects decreased with age and ranged between 0.116 to 0.186 and 0.060 to 0.115 respectively. Phenotypic correlations ranged from 0.233 to 0.944 and genetic correlations ranged from 0.356 to 0.922. Weighted least-squares analysis was done to study the effects of non-genetic factors where the distance from the equator was found to significantly affect all the heritability traits. Weighted estimates obtained from this study could be beneficial during the implementation phase of a breeding program which is designed for the genetic improvement of sheep breeds in the tropics.