HERITABILITY AND REPEATABILITY FOR MILK-PRODUCTION TRAITS OF JAPANESEHOLSTEINS FROM AN ANIMAL-MODEL

Records of the first three lactations of cows were obtained from the f ile of the Dairy Herd Testing Association in Hokkaido. The data were d ivided into 10 files containing approximately 24,000 cows each. The de rivative-free REML method was used to estimate variances with a repeat ability model. The model contained herd-year, calving month, and the l inear and quadratic effects of age at calving as fixed effects; additi ve genetic, permanent environmental, and temporary environmental effec ts were the random effects. Estimates from the 10 data files were pool ed into a simple arithmetic mean. Empirical standard errors were calcu lated from the samples. Average estimates of heritability were the sam e for milk and fat yields (h2 = .30). Heritabilities for protein (h2 = .26) and SNF yields (h2 = .27) are slightly lower than those for milk and fat yields. Estimates of repeatabilities, .52 to .54, are conside rably different from those now used for genetic evaluations in Japan.