Genetic and phenotypic relationships between fertility and wool production in 2-year-old Merino sheep

Abstract

Records of the lambing and weaning performance (fertility) of 2-year-old Peppin Merino ewes were analysed. Repeatability and heritability of number of lambs born and weaned were low. Heritability of number of lambs born was significantly different from zero (0.20 ± 0.10). Phenotypic and genetic correlations between the fertility traits and greasy wool weight, all measured at approximately 15 months of age, were calculated. Phenotypic correlations between number of lambs born or weaned and greasy wool weight were negative and significant. The phenotypic correlation between number of lambs weaned and clean wool weight was negative and significant. Significant negative genetic correlations were found between number of lambs born and both greasy wool weight and clean wool weight. Genetic correlations between number of lambs weaned and the fleece and body traits had very large standard errors. The results were used to estimate correlated responses in fertility resulting from selection for greasy wool weight, clean wool weight, and body weight of –0.08i, –0.13i, and 0.03i respectively.