An analysis of sire-son and dam-daughter relationships for type traits in the Holstein descriptive type classification system

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Virginia Polytechnic Institute and State University

Age correction factors were developed from 336,253 individual classification results and were applied to final score, final classification, general appearance, dairy character, body capacity, and mammary system. Using a within-herd model, 30,715 daughter dam pairs were 2 analyzed to determine estimates of heritability (h²) and genetic and phenotypic correlations. Heritability estimates were: final classification, 0.31; final score, 0.25; general appearance, 0.26; dairy character, 0.15; body capacity, 0.23; mammary system, 0.20; stature, 0.38; head, 0.11; front end, 0.11; back, 0.14; rump, 0.21; hind legs, 0.07; feet, 0.08; fore udder, 0.16; rear udder, 0.17; udder support, 0.13; udder quality, 0.04; and teats, 0.17. When traits were expressed as 1 for desirable and 0 for undesirable, h² estimates were lower. Genetic correlations were generally positive, ranging from 1.01 ± 0,08 between final score and final classification to -0.17 ± 0.22 between dairy character and udder quality expressed as a binomial.

Regression of the son progeny test on that of his sire indicated that head, front end, hind legs, feet, rear udder, and udder quality were poor indicators of son's performance when the sire's progeny test result was used for selection decisions. Considerable emphasis was placed on type in selecting sires of sons, especially for final score, hind legs, fore udder, udder support, and teats, since bulls whose daughters scored high in these traits sired more future sires than other bulls.