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 and did not indicate the need for using different heritability values to predict progress from selection, or to develop selection procedures for herds with different production levels.

Abstract

SU~%[~£ARYIntra-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.There was no significant relationship between the heritability values and the production levels for the groups of herds in any of the breeds.Heritability estimates obtained by pooling the results from each breed were: Guernsey, 0.21 .06;Holstein, 0.22 +---.04; and Jersey, 0.24 ± .05.These results do not indicate the need for using different heritability values to predict progress from selection, or to develop selection procedures for herds with different production levels.