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Components of Genetic Variation for Descriptive Type Traits of Holsteins^{1, 2,}

Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg 24061

ABSTRACT

Data consisted of first available classification scores for 12 descriptive type traits on 298,875 registered Holstein cows and their dams. Traits were final score, stature, head, front end, back, rump, hind legs, feet, fore udder, rear udder, udder support, and teats.

Covariances among cow-dam pairs, full-sisters, paternal half-sisters, and maternal half-sisters were used to estimate four components of genetic variation for the 12 type traits. Genetic components of variance produced by additive direct, dominance direct, additive maternal, and covariance between additive direct and additive maternal effects were estimated.

Heritabilities from sire components of variance ranged from .39 for final score to .06 for hind legs with all traits except final score and stature less than .25.

Dominance effects ranged from 2 to 6 times as great as additive variation whereas additive maternal effects were similar to additive direct effects. Effects due to additive direct by additive maternal covariance effects were small but consistently negative.

¹ Published with the approval of the Dean and Director of the College of Agriculture and Life Sciences and the Agricultural Experiment Station.

² Supported in part by a grant from the Holstein Association of America.

³ Department of Dairy Science, Louisiana State University, Baton Rouge 70803.

⁴ Director, Program Development and Research, Holstein Association of America, Brattleboro, VT 05301.