Estimation of Genetic Parameters of Body Weight and Body Size in Different Stages of Pishan Red Sheep

As a dual-purpose (meat and fat) coarse-wool sheep breed in Xinjiang, the Pishan Red sheep exhibits year-round estrus and excellent reproductive performance. The aim of this study was to systematically estimate the genetic parameters of growth traits in Pishan Red sheep at each stage from 0 to 12 months of age, and to provide a scientific basis for optimizing early selection indices for this breed. Year of birth, type of birth, and sex were included as fixed effects, while maternal genetic effects and individual additive genetic effects were treated as random effects. A multi-trait animal model was constructed using DMU 6.0 software to analyze the genetic parameters. The results showed that for growth traits at 0 months of age, heritability ranged from 0.09 to 0.64, genetic correlations from –0.03 to 0.84, and phenotypic correlations from 8.2 × 10−3 to 0.32. Among these, the direct heritability of body weight was 0.18, and the maternal heritability was 0.21, while cannon circumference was identified as a high-heritability trait. At 2 months of age, heritability ranged from 0.04 to 0.69, genetic correlations from −0.78 to 0.96, and phenotypic correlations from 0.036 to 0.44. Body weight, body length, and cannon circumference were high-heritability traits. At 6 months of age, heritability ranged from 0.04 to 0.71, genetic correlations from −0.32 to 0.70, and phenotypic correlations from −0.13 to 0.54. Body weight was a medium-heritability trait, while chest width and cannon circumference were high-heritability traits. At 12 months of age, heritability ranged from 0.07 to 0.48, genetic correlations from −0.04 to 0.87, and phenotypic correlations from 0.28 to 0.72. Body weight was a medium-heritability trait, whereas body height, body length, cannon circumference, and heart girth were high-heritability traits. Both body weight and cannon circumference exhibited high heritability throughout the 0–12 month period and can therefore serve as key selection indices for early breeding in this breed. The findings of this study provide essential local baseline data for the genetic improvement, breeding program design, and genetic evaluation of Pishan Red sheep.