J. Anim Sci.
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J. Anim Sci. 1978. 47:853-857.
© 1978 American Society of Animal Science
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Effect of Inbreeding on within-Herd Genetic Evaluation of Beef Cattle

E. J. Pollak and G. R. Ufford

University of California1, Davis 95616

Abstract

The effects of inbreeding of dam and calf on sire evaluations were examined for 2,921 weaning weight records from Hereford cattle. Two models were considered; one including regressions for both sources of inbreeding and the second excluding the regressions. The basic model contained age of dam by sex of calf subclasses, years, sire and dam groups, regression on calf age at weaning, sires and dams.

Regression coefficients of weaning weight on inbreeding of dam and calf were –.3 and –.25 kg/percent inbreeding, respectively. Both estimates indicate an inbreeding depression in performance for weaning weight. In the dam this depression may be in the form of decreased milk production, and in the calf a depression in direct growth performance.

Including the regressions of inbreeding of dam and calf in the model affected the comparisons of sires imported into the herd (hence unrelated to mates) with sires raised on the ranch. Sires and dams raised on the ranch were grouped by year of birth in 5-year and 2-year increments, respectively. Neither within group or between group comparisons of these sires were affected by including the regressions for inbreeding. Dam group solutions changed when including the inbreeding regressions by the magnitude predicted from the difference in the average inbreeding coefficients observed between group 1, representing the base generation dams, and other groups.

Footnotes

1 Department of Animal Science.






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Copyright © 1978 by the American Society of Animal Science.