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Influence of Sex, Season of Birth and Age of Dam on Economic Traits in Range Beef Cattle^{1, 2}

U. S. Department of Agriculture

Abstract

The purpose of this study was to evaluate the influence of sex, season of birth, and age of dam on birth weight, weaning weight, gain from birth to weaning, weaning score, fall yearling weight, and fall yearling score for range Hereford cattle.

Male calves were 5.6 lb. heavier at birth and 26.2 lb. heavier at weaning than heifer calves. The sex difference in weaning score was negligible.

The regressions of birth weight, gain from birth to weaning, and weaning score on weaning age (the inverse of time born during the calving season) were –.08 lb. per day, –.04 lb. per day, and 0.1 unit per day, respectively. All regressions were considered to be too small for practical importance.

The age of dam had a marked influence on all traits studied except fall yearling score. The cow's production with regard to birth weight, weaning weight, and weaning score increased steadily from 3 to 6 years of age and then declined. Additive correction factors are presented for adjusting records to mature (6-year-old) basis.

¹ Contribution from the Western Regional Project W-1, "The Improvement of Beef Cattle Through Breeding Methods."

² Acknowledgement is made to Superintendent J. R. Quesenberry, U. S. Range Livestock Experiment Station, Miles City, Montana, under whose supervision the data for this study were collected in cooperation with the Montana Agricultural Experiment Station, and to the Nebraska Agricultural Experiment Station for providing staff time.

³ Department of Animal Husbandry, University of Nebraska.