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The Importance of Sire x Sex Interactions for Preweaning and Weaning Traits¹

University of Missouri³, Columbia 65201

Abstract

The importance and magnitude of sire x sex interaction effects in beef sire evaluation for birth weight (BW), average daily gain to weaning (ADGW) and 210-day weight were investigated through the estimation of various parameters. Data from 902 Hereford calves (433 and 469 ) from 17 sires born at the Weldon Springs Station, Missouri during the 1961 to 1967 calving seasons were available for this study. The data were transformed to deviations from year-season-age of dam group averages in each sex before analysis. Separate analyses were made with one-way and two-way classifications.

The sire x sex interactions for BW were significant at P<.10. The interaction and sire effects were of small magnitude, the latter being relatively more important and highly significant. The heritability estimate for BW was higher in female than male calves but the difference was not significant, indicating that the sex of progeny did not affect the evaluation of sires for BW.

For ADGW, sire x sex interactions as well as sire effects were significant, although of small magnitude. The former, however, was relatively more important. The heritability estimate for ADGW was higher in male calves but the difference was not significant, suggesting that an equal number of progeny from either sex should be used in progeny testing sires for this trait.

The 210-day weights showed significant sire x sex interaction effects. However, each of the effects contributed only a small fraction of the total variance, with the interaction variance component about twice that of sires. The estimate of heritability for this trait was of low magnitude and almost identical in both sexes. Thus equal numbers of male and female calves should be used in the evaluation of sires on the basis of the 210-day weights of their progeny.

¹ Contribution from the Missouri Agricultural Experiment Station. Journal Series No. 7114. Approved by the Director.

² Present address: Department of Animal Breeding and Genetics, Orissa University of Agriculture and Technology, Bhubaneswar-751003, Orissa, India.

³ Department of Animal Husbandry.