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Effects of Corrective Mating 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 of 107,486 registered Holstein cows and their dams. Each cow record also contained progeny test scores of the sire of the cow.

Corrective mating was defined as mating dams with undesirable phenotypes to sires with significantly desirable progeny test scores for type. Corrective mating was evaluated by changes from breed average of frequency distributions of types of offspring in one generation. Corrective mating with Predicted Difference Type as a breeding strategy including sire selection and corrective mating also was evaluated by changes from breed average of frequency of offspring types.

For most types of dams, corrective mating produced significantly fewer daughters than breed averaged coded desirable. However, corrective mating did produce sizable increases of the frequency of desirable types of female offspring over female parents. Therefore, it may be useful as a selection scheme. Corrective mating by Predicted Difference Type produced distributions of offspring similar to those produced by sire selection for each individual descriptive trait.

Correlations between dam's classification score and sire's progeny test score were larger than .6 for stature and less than .5 for final score, back, and teats. Correlations for all other traits were near zero.

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.