Estimates Using an Animal Model of (Co)variances for Yields of Milk, Fat, and Protein for the First Lactation of Holstein Cows in California and New York

Abstract

First lactation yields of milk, fat, and protein from Holstein cows in New York and California were used to obtain REML estimates of (co)variances for yield traits using a multitrait animal model. Data from each state were split randomly into 10 samples, averaging 5504 cows per sample from California and 5078 from New York. Mean heritability estimates for milk, fat, and protein yields were .30 ± .02, .31 ± .01, and .29 ± .01 for California data and .33 ± .01, .35 ± .01, and .30 ± .01 for New York data. Averages of genetic correlation estimates for California and New York were .63 ± .01 and .52 ± .02 between milk and fat, .84 ± .01 and .83 ± .01 between milk and protein, and .73 ± .01 and .68 ± .01 between fat and protein. Estimates of environmental correlations were larger than estimates of genetic correlations. Mean estimates of phenotypic correlations for California and New York were .75 ± .01 and .72 ± .01 between milk and fat, .92 ± .01 and .91 ± .01 between milk and protein, and .81 ± .01 and .79 ± .01 between fat and protein yields. On average, these estimates agree with those obtained from animal models with limited rounds of iteration for small data files. © 1995, American Dairy Science Association. All rights reserved.