Estimation of (co)variance components for body weight traits in intercross synthetic sheep

Abstract

This study was carried out on the recently developed intercross sheep developed from Bharat merino and Gaddi sSynthetic in the temperate region in the state of Himachal Pradesh of India. Study aimed to estimate the genetic parameters and (co)variance components for body weights at birth (BW) and 3-month (3BW), 6-month (6BW), 9-month (9BW) and 12-month (12BW) month age in a closed flock of intercross sheep maintained at North Temperate Regional Station of ICAR-CSWRI, Garsa, India. Data records on 1505 sheep descended from 565 dams and 154 sires over the period of 10 years were utilized. Data were corrected for possible fixed environmental effects such as lambing year, parity, sex of lamb, ewe weight at lambing for further genetic analysis. The restricted maximum likelihood procedure fitting animal models with different combinations of direct and maternal effects were used for genetic analysis. Analysis revealed significant influences of lambing year, parity, sex of lamb and ewe weight at lambing on studied traits. Direct heritability estimates for BW, 3BW, 6BW, 9BW and 12BW were 0.14±0.04, 0.18±0.05, 0.00±0.04, 0.05±0.05 and 0.05±0.05, respectively. Maternal effects significantly influenced the BW and estimated maternal heritability for the trait was 0.17±0.03. The correlation among body weights were medium to high except between BW and 12BW and it ranged from 0.16±0.51 to 0.99±0.19. Results suggest that maternal effects were important for initial growth performance. The heritability estimates for weaning weight was moderate and its positive association with other growth traits indicated that the present selection practice at six months may be shifted to early selection at weaning weight for further genetic improvement.

Keywords

• Body weights, Direct heritability, Genetic correlation, Intercross sheep, Maternal effects