Estimation of genetic parameters and trends in performance traits of Rambouillet sheep

Genetic parameters and trends are very important to know about the genetic gain and effectiveness of the selection. The present study was conducted on 8,872 records of Rambouillet sheep maintained at Government Sheep Breeding and Research Farm, Reasi, Jammu, Jammu and Kashmir, India over a period of 20 years from 1996 to 2015. The performance traits studied in the present investigation were birth weight (BW), weaning weight (WW), nine-month body weight (9BW), twelve month body weight or yearling weight (YW) and annual wool production (AWP). Heritability, genetic correlations and genetic trends were estimated. Estimates of heritability ranged from medium (0.192 for AWP) to very high (0.720 for 9BW). The highest genetic and phenotypic correlations were obtained between 9BW and YW indicating that early selection on the basis of 9BW will improve the YW simultaneously. AWP had negative genetic correlations with all other traits except for WW. The genetic trends over the years were positive for BW and WW; and negative for 9BW, YW and AWP. The phenotypic trends for all the performance traits in the present study were negative. The effect of genetic trend was non-significant for all the traits. The R2 value was very low to medium. The phenotypic trends over the years were negative for all the traits except for YW. The genetic and phenotypic trends of the present study indicate that environment plays an important role in controlling different performance traits of Rambouillet sheep.