ESTIMATION OF GENETIC-PARAMETERS FOR MILK-YIELD AND FAT AND PROTEIN CONTENTS OF MILK FROM MURCIANO-GRANADINA GOATS

A total of 10,289 lactations, corresponding to 4967 does distributed i n 35 herds, was used to estimate heritabilities, repeatabilities, and correlations among milk yield (kilograms), fat contents, and protein c ontents (grams/100 g of milk) with single-trait and multiple-trait ani mal models using repeated records. Single-trait estimates were similar to those obtained with multiple-trait analysis. Heritabilities were 0 .18, 0.16, and 0.25 with single-trait analysis and 0.17, 0.14, and 0.2 2 with multiple-trait analysis for milk yield, fat content, and protei n content, respectively. Repeatabilities were 0.39, 0.36, and 0.47 wit h single-trait analysis and 0.36, 0.33, and 0.41 with multiple-trait a nalysis for milk yield, fat content, and protein content, respectively . Genetic correlations were -0.89 between milk yield and fat content, -0.65 between milk yield and protein content, and 0.93 between fat and protein contents. Phenotypic correlations were -0.48 between milk yie ld and fat content, -0.47 between milk yield and protein content, and 0.54 between fat and protein contents. Heritabilities and repeatabilit ies were lower, and correlations were higher, than those found in the literature. Some combination of both EBV of milk yield and protein con tent would be a good criterion for selection to improve milk yield whi le maintaining fat and protein contents.