Environmental and genetic effects on growth traits of Chokla sheep

摘要

Data on 1810 Chokla sheep, maintained at the Central Sheep and Wool Research Institute (CSWRI), Avikanagar, Rajasthan, collected for a period of 21 years (1980 through 2000) were used to study growth traits and genetic control. The average weights at birth, 3, 6, 9 and 12 months of age were 2.73 +/- 0.04, 12.74 +/- 0.22, 16.71 +/- 0.26, 18.20 +/- 0.26 and 21.81 +/- 0.35 kg, respectively. Significant effects associated with the period of birth, parity of dam, season of birth and sex of lambs were observed on body weight at different stages of growth. Sire of the lamb contributed significantly on all body weights under study. There were marked periodic differences in the different growth traits of lambs. The lambs born in the dam's third and later parities were significantly heavier to those born in first or second parities. Season of birth had significant effect on body weights at 3, 9 and 12 months of age. Males were heavier than females at almost all stages of growth and the sex differences tended to increase with age. The heritabilities of body weights at birth and at 3, 6, 9 and 12 months of age were high in magnitude, ranging from 0.32 to 0.48, which indicate the ample scope of improvement of these traits by selection. The medium (0.17 +/- 0.16) to high (0.89 +/- 0.05) genetic correlation among the body weights at different stages in this study suggest that selection for increased early growth traits will lead to genetic improvement in the subsequent development of body weights.