UNIVARIATE AND MULTIVARIATE PARAMETER ESTIMATES FOR MILK-PRODUCTION TRAITS USING AN ANIMAL-MODEL .1. DESCRIPTION AND RESULTS OF REML ANALYSES

Using production records in lactations 1-3 from 100 large Holstein-Friesian pedigree herds, parameters for milk, fat and protein yield in lactations 1-3 were estimated with REML using an animal model. The number of records for each lactation was 38 81 1, 26 223 and 16 542 for lactation 1, 2 and 3 respectively. Heritabilities for the 3 yield traits were similar: approximately 0.36 in lactation 1 and 0.30 in lactations 2 and 3. Genetic correlations between yield traits in lactations 1 and 2, for example between milk production in first and second lactations, were approximately 0.86. Genetic correlations between yield traits in lactations 2 and 3 were near unity. Genetic correlations between yield traits within lactations ranged from 0.58, for milk and fat yield in lactation 3, to 0.91, for milk and protein yield in lactation 1. Genetic correlations between yield traits between lactations ranged from 0.55, for milk yield in lactation 1 and fat yield in lactation 2, to 0.85., for milk yield in lactation 2 and protein yield in lactation 3. Environmental correlations between traits within lactations were approximately 0.95, and approximately 0.40 across lactations.