Sexual dimorphism in early body weight traits of Raeini Cashmere goat: sex-specific heritability and cross-sex correlations

Pedigree and body weight records collected from 1979 to 2013 at the Breeding Station of Raeini Cashmere goat, south-east of Iran, were used for investigating genetic aspects of sexual dimorphism (SD) for birth weight (BW), weaning weight (WW) and six-month weight of the breed. The SD levels, calculated as male/female ratio at birth, weaning, and six months of age, were 1.08, 1.14, and 1.16, respectively. Genetic analyses for investigating the SD performed by applying six bivariate animal models included different combinations of direct additive genetic, maternal additive genetic, and maternal permanent environmental effects. Estimates of phenotypic variance ( ) were different between males and females and were more pronounced at weaning and six months of body weight. For all studied traits, direct additive genetic, residual, and phenotypic variances in male kids were higher than in female kids. Direct heritability estimates for BW, WW, and 6MW in male kids were 0.24, 0.17, and 0.10, respectively. The corresponding estimates in female kids were 0.21, 0.21, and 0.09, respectively. Cross-sex differences for direct heritability estimates for the studied traits were statistically non-significant, implying that body weight traits could be considered the same in male and female Raeini Cashmere kids. The estimates of between-sex correlations for each trait were positive and statistically significant. Direct genetic correlations between sexes were 0.90, 0.87, and 1.00 for BW, WW, and 6MW, respectively, indicating that selection for the investigated body weights in male kids would result in a correlated response in females and, consequently, would prevent phenotypic divergence. Furthermore, the high cross-sex genetic correlations for each trait implied a similar genetic structure in both sexes.