Direct and maternal effects models for variance components and genetic parameters estimation of growth traits in prolific Garole sheep

The objective of the study was to identify the mostsuitable model for estimation of (co) variance components and genetic parameters of different growth traits in prolific Garole sheep. Growth data of 1,058 Garole lambs born to 49 sires and 208 ewe was collected from ICAR-Central Sheep and Wool Research Institute (ICAR-CSWRI), Avikanagar, India. The traits studied were birth weight (BWT), 3 month weight (3WT), 6 month weight (6WT), 9 month weight (9WT), 12 month weight (12 WT), average daily gain from birth to 3 month age (ADG1), average daily gain from 3 month to 6 month age (ADG2). Twelve different animal models were fitted to account for different direct genetic and maternal effects. Model including maternal permanent environmental effect, maternal temporary environmental effect and direct genetic effects (Model 8) was most appropriate model for BWT. For other traits model with direct genetic effect and common litter effect (Model 7) was found most suitable. From best model direct heritability estimates of 0.037 +/- 0.054, 0.148 +/- 0.075, 0.104 +/- 0.077, 0.079 +/- 0.083, 0.103 +/- 0.116, 0.137 +/- 0.072 and 0.045 +/- 0.071 were obtained for BWT, 3WT, 6WT, 9WT, 12WT, ADG1and ADG2, respectively. Maternal temporary environmental effect variance contributed highest to total phenotypic variance. It ranged from 0.347 +/- 0.040 for BWT to 0.451 +/- 0.083 for 9WT. Estimates of direct genetic correlation ranged from -0.047 for BWT-ADG1 to 1.00 for BWT-12WT, 6WT- 12WT and 9WT-12WT. Phenotypic correlations were positive and varied from 0.119 for ADG1-ADG2 to 0.982 for 3WT-ADG1. The growth traits of Garole sheep have low to moderate heritability and were influenced by maternal temporary environmental effect due to sharing of common litter environment.