Evaluating animal models comprising direct and maternal effects associated with growth rates and the Kleiber ratio in Harnali sheep

The present work evaluated animal models comprising direct and maternal effects to estimate (co)variance components and genetic parameters of growth rates and Kleiber ratio in Harnali sheep. The information on pedigree and targeted traits of 1862 lambs born to 144 sires and 591 dams was collected for the period from 1998 to 2018. The traits studied were average daily gain from birth to 3 months of age (ADG(1)), 3 months to 6 months of age (ADG(2)), and 6 months to 12 months of age (ADG(3)) and their corresponding Kleiber ratios as KR1, KR2 and KR3, respectively. The statistical methods included the general linear model for analyzing the effects of fixed factors and animal models for deriving variance components for targeted traits. According to best model evaluated on the basis of likelihood ratio test, the estimated direct heritability was low in magnitude and ranged from 0.04 to 0.14. Direct heritability estimates for ADG(1), ADG(2), ADG(3), KR1, KR2 and KR3 were 0.06, 0.14, 0.05, 0.04, 0.11 and 0.05, respectively. The maternal genetic effects contributed (4-7%) significantly for ADG(1), KR1 and KR2 traits. The genetic correlations ranged from -0.35 +/- 0.11 (ADG(1)-KR2) to 0.98 +/- 0.01 (ADG(2)-KR2 and ADG(3)-KR3) and phenotypic correlations ranged from -0.36 +/- 0.02 to 0.98 +/- 0.01 for ADG(1)-KR2 and ADG(2)-KR2, respectively. The significant maternal effects along with low levels of direct effects for average daily gain and Kleiber ratio at different age group should be considered while setting selection and managerial strategies to achieve anticipated growth rates in Harnali sheep.