Relationships between herd type and genetic and environmental variances in Holsteins.

ABSTRACT

Type classification data from the Holstein Association of Canada on 354,308 daughters of 13,694 sires were subdivided into 20 groups of approximately equal size according to herd average final score. Genetic and environmental variances were estimated for each group by Henderson's new method. Traits considered and their heritabilities averaged over groups were final score .13; final class .11; dairy character .17; capacity .24; rump .16; feet and legs .10; mammary system .12; fore udder .12; rear udder .12; size .31. Regressions of genetic variances on group number ordered according to herd final score indicated significant trends only for rump and feet and legs for which higher genetic variances were found for higher type scores. Regressions of environmental variances on group number were significant for all traits. Higher environmental variances were found for lower final scores, final class, dairy character, and capacity, but the opposite was observed for size. The distribution of environmental variances across groups was U-shaped for rump, feet and legs, for udder, and rear udder; lowest variances were associated with intermediate scores for overall type.