Abstract
This study aimed to quantify autosomal and sex-linked genetic parameters for early growth traits in the Murciano-Granadina goat breed. Data were collected from a commercial dairy herd in Ghaleh-Ganj, southern Iran. A total of 19,582 records for birth weight (BWT) and 9157 records for weaning weight (WWT) were analyzed, covering animals born between 2016 and 2023, descended from 460 bucks and 5382 does. Live weight measurements were used to calculate preweaning growth rate (PWGR), preweaning Kleiber ratio (PWKR), and preweaning growth efficiency (PWGE). Environmental effects were evaluated using aov package in R, and the optimal multivariate model was constructed by combining the best-fitting univariate models for each trait. Genetic parameters were estimated using this optimal multivariate animal model and the average information restricted maximum likelihood algorithm in WOMBAT software. Estimated direct autosomal heritabilities ( ha2 ) were 0.05 for BWT, 0.08 for WWT, 0.06 for PWGR and PWGE, and 0.09 for PWKR. Corresponding direct sex-linked heritabilities ( hs2 ) were 0.03 for BWT, 0.02 for WWT, 0.01 for PWGR, and PWKR, and 0.04 for PWGE. Excluding sex-linked chromosomal effects from optimal model led to a 3-14 % increase in autosomal additive genetic variance and a 7-20 % increase in the residual variance. Autosomal genetic correlations (r(a)) ranged from -0.70 (BWT-PWGE) to 0.83 (PWKR-PWGR), while sex-linked genetic correlations (r(s)) ranged from -0.75 (BWT-PWGE) to 0.93 (WWT-PWGE). These findings highlight the relevance of accounting for sex-linked additive inheritance in genetic evaluations, supporting more informed selection decisions and contributing to improved genetic progress in Murciano-Granadina goats.