Estimation of genetic parameters for pre-weaning growth traits in Dorper sheep under local Chinese conditions

This study aimed to estimate non-genetic factors, variance components, and genetic parameters, including heritability, genetic/phenotypic correlations for birth weight (BW), weaning weight (WW), average daily gain (ADG), and Kleiber ratio (KR) traits of Dorper sheep under localized Chinese conditions.

Data from 2,022 Dorper sheep lambs, collected between 2019 and 2021 at Inner Mongolia Sano Sheep Breeding Co., Ltd. were analyzed. Traits included BW, WW adjusted to 90 days, ADG, and KR. Generalized linear model (R 4.3.1) assessed non-genetic factors, including recipient dam age, sex, birth year, month, and herd. Six animal models were evaluated using ASReml's AIREML to determine the most suitable model for estimating genetic parameters while bivariate models were utilized to analyze genetic and phenotypic correlations.

Recipient dam age, sex, birth year, month, and herd significantly affected all traits (p<0.05). Model 2, which incorporates direct additive genetic and maternal permanent environmental effects, was determined to be optimal. Heritability was low (BW: 0.0215; WW: 0.0287; ADG: 0.0391; KR: 0.0504). BW showed a negative genetic correlation with WW, ADG, and KR. In contrast, WW showed a strong positive genetic correlation with ADG (0.9952) and KR (0.9984), along with high phenotypic correlations with these traits (0.9829 and 0.8819, respectively).

The low heritability limits direct selection for pre-weaning traits. Prioritizing WW enhances indirect genetic gains for ADG and KR, facilitating the optimization of Dorper sheep breeding strategies under Chinese intensive systems.