Heritability of Fat Yields in Herds with Different Production Levels

Intra-herd-sire heritability estimates were computed to examine the relationship between these values and the herd level of fat yield for 1,825 Guernsey, 5,458 Holstein, and 3,465 Jersey daughter-dam pairs. Phcnotypie and additively genetic variances showed a definite increase as the mean fat production for the herd increased, and in the Jersey data the correlation between the mean fat yield for the herd and the intra-herd-year variance was 0.46 --+ .05. The coefficient of variation, however, declined for the higher herd levels.