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Sire Effects for Specific Combining Ability in Purebred and Crossbred Cattle¹

Brooksville Beef Cattle Research Station, A.R.S., U.S.D.A., Brooksville, Florida 33512 and University of Florida, Gainesville 32601

Abstract

Specific combining ability of individual sires was evaluated from sire x breed-of-dam interaction effects and the genetic correlation between half-sib family means using data from purebred and backcross progeny. The traits studied were pre-weaning condition score, birth weight, 205-day weight and post-weaning gain ratio. A total of 2,083 progeny were evaluated.

Sire x breed-of-dam interaction effects were non-significant for all analyses with an average F ratio of 1.06. The estimated genetic correlations between paternal half-sib families from different classes of dams varied from .56 to 1.24 for an average of .96. These data suggest that differences among sires of the same breed for specific combining ability were not large enough to be of economic importance, that progeny testing procedures sensitive enough to effectively improve specific combining ability would be difficult to achieve and that evaluating sires on the basis of straightbred or crossbred progeny would be of nearly equal effectiveness in improving additive genotypic value.

¹ Contribution from the Southern Regional Beef Cattle Breeding Project, S-10, Florida Agricultural Experiment Station Journal Series #5348.

² University of Florida.

³ Brooksville Beef Cattle Research Station.