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Specific Combining Ability Among Dairy Sires for Type Traits¹

Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada

ABSTRACT

Type records of 12,030 Canadian Holstein cows in first lactation with both sires and maternal grandsires in a group of 200 artificial insemination sires were analyzed to determine the importance of specific combining ability. Data were adjusted for effects of round of classification, age, stage, and season of classification before final analysis. Magnitude of the component of variance for sire by maternal grandsire interaction was the criterion to evaluate the importance of specific combining ability. This component of variance explained 7.3, 2.5, 2.4, 1.7, 2.1, 2.3, 2.0, 1.8, .8, 2.3, and 6.0% of the variance in adjusted records for final score, final classification, general appearance, dairy character, body capacity, mammary system, fore udder, rear udder, legs and feet, rump, and body size. A least squares study of interaction among sires and maternal grandsires used extensively in Ontario studs revealed no practically important interaction effects for any of the traits.

¹ Based on the M.Sc. thesis of the senior author and financed in part by the Ontario Ministry of Agriculture and Food and the ministry of Colleges and Universities.