GENETIC-PARAMETERS FOR MILK-YIELD IN DAIRY SHEEP

A repeatability animal model and restricted-maximum-likelihood methods were used to estimate genetic parameters of milk yield in dairy sheep. A total of 14 388 lactation records of 4123 ewes from three Churra flocks with full pedigree information for many years were considered. The following estimates were obtained for each flock: repeatability: 0.43, 0.32, and 0.32; percentage of permanent environmental variance: 14.3%, 17.3%, and 16.8%; heritability: 0.29, 0.15, and 0.15; coefficient of additive genetic variation: 13.6%, 11.8%, and 11.2%. When the additive genetic variation coefficient is taken into consideration, the estimates obtained could allow one to expect that the response to selection using a repeatability model for dairy-sheep-breeding programmes may be relatively high.