Evaluation of genetic and maternal effects on growth-related traits in Sonadi sheep.

Efficient growth of indigenous sheep is vital for productivity and sustainability in arid and semi-arid environments. Sonadi sheep, native to Rajasthan, India, contribute significantly to rural livelihoods; however, genetic evaluations incorporating maternal effects remain limited. This study estimated direct and maternal genetic parameters for average daily gain (ADG), Kleiber ratio (KR), growth efficiency (GE), and relative growth rate (RGR) across pre-weaning (0–3 months), early post-weaning (3–6 months), and late post-weaning (6–12 months) phases in 1,834 lambs using six univariate animal models fitted by restricted maximum likelihood. The model selection was based on the Akaike Information Criterion and statistical stability. Models incorporating direct–maternal covariance produced boundary correlations (ram ≈ − 1) and were excluded from interpretation. Under stable models, direct heritability ranged from 0.09 to 0.28 for ADG, 0.18–0.33 for KR, 0.24–0.31 for GE, and 0.23–0.33 for RGR, indicating moderate additive genetic variation. Maternal influence was more pronounced pre-weaning and declined with age. Sex, lambing season, and dam weight significantly influenced growth performance. Genetic correlations were consistently high (0.96–0.98), and phenotypic correlations were slightly lower (0.91–0.95); however, as KR, GE, and RGR share common body weight components, algebraic dependence warrants cautious interpretation. Pre-weaning ADG was the most practical primary selection criterion, with KR, GE, and RGR serving as complementary indicators. These baseline estimates may support breeding objectives for sustainable meat production in semi-arid regions of India.