Genetic parameter estimates for reproductive traits in Chokla ewes of India

Early selection of ewes for better reproductive performance may reduce generation interval and increase genetic gains. Considering this, the present study aimed to derive the genetic parameter estimates of ten reproductive traits in 1172 maiden Chokla ewes over a period of 22 years. Initially, the traits, namely age at first service (AFS), weight at first service (WFS), age at first successful service (ASS), weight at first successful service (WSS), age at first lambing (AFL), ewe's weight at first lambing (WFL), first lambing interval (LI1), first service period (SP1), first parity lamb survival (SUR1) and first service fertility rate (FER1) were analysed for the effects of genetic and non-genetic factors. The significant effects were fitted into six animal models to estimate the genetic parameters. The heritability estimates were low for the age traits and FER1 (0.06-0.09) but moderate for the rest of the traits (0.16-0.23), indicating the suitability of these traits for improvement through direct selection. The maternal direct and permanent effects were meagre for all the traits. The ewe weights had strongly negative correlations with the age of sexual maturity and positive correlations with lamb survival. The results emphasise the need to optimize the weights of maiden ewes to improve reproductive performance.