Unraveling Sexual Size Dimorphism in Growth Traits of Dairy Goats: A Genetic Evaluation That Accounts for Dominance Effects

Sexual size dimorphism (SSD) is a major determinant of growth and productivity in domestic animals, yet dominance genetic effects have rarely been incorporated into its evaluation in goats. This work presents an extensive analysis of SSD in Murciano‐Granadina (MG) goats for pre‐weaning growth traits, birth weight (BWT), weaning weight (WWT), average daily gain (ADG), Kleiber ratio (KR), and growth efficiency (GE) through genetic models including additive, dominance, and maternal components. Data from 17 404 kids of 337 sires and 3966 dams indicated pronounced SSD as males were 9% heavier at birth, 4% heavier at weaning, and 6%–11% higher for ADG, KR, and GE. Models including dominance effects provided better fit, with dominance heritabilities ( = 0.12–0.54) exceeding additive ones ( = 0.03–0.14), highlighting significance of nonadditive genetic variance. Maternal effects were trait‐ and sex‐specific ( = 0.04–0.18). Cross‐sex additive genetic correlations () were usually high (0.73–1.00), whereas dominance correlations were moderate to high (0.44–0.92), indicating partial sex‐specific nonadditive effect. Traits that were lower in like BWT and WWT revealed higher potential of divergence under sex‐specific selection. Comparisons of sex‐joint and sex‐specific evaluations indicated substantial re‐ranking of top sires for WWT and BWT, moderate re‐ranking for ADG and minimal changes for KR and GE. Overall, while sex‐joint models are suitable for standard evaluation work, integrating dominance effects and sex‐specific models improves selection accuracy of SSD traits, offering a practical framework to refine genetic evaluations and optimize breeding programs in dairy goats.