J. Anim Sci.
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J. Anim Sci. 1964. 23:562-568.
© 1964 American Society of Animal Science
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Genetic Analyses of Economic Traits Measured in Range-Raised Herefords at Preweaning and Weaning Ages1

O. F. Pahnish, R. L. Roberson, R. L. Taylor, J. S. Brinks2, R. T. Clark2 and C. B. Roubicek

The University of Arizona, Tucson, and U. S. Department of Agriculture

Abstract

Heritabilities of preweaning and weaning traits within sex and with sexes combined were estimated by the paternal half-sib method from a four-year set of data representing 350 heifer progeny and 370 bull progeny of 17 Hereford sires. Correlations (genetic, environmental and phenotypic) plus direct and correlated responses were computed within sex. The heritability of birth weight was 0.14 and 0.32 for heifers and bulls, respectively. The estimate with sexes combined was 0.20. Heritabilities of daily gain from birth to weaning, weaning weight, weaning grade and weaning condition of heifers ranged from 0.23 to 0.32. The corresponding heritabilities for bulls were all less than 0.10. The heritability estimates over sexes for weaning traits ranged from 0.05 to 0.13. With two exceptions, corresponding within-sex correlations (genetic, environmental and phenotypic) agreed in sign. The discrepancies in sign were obtained in estimates of genetic correlations of weaning grade with daily gain from birth to weaning and weaning weight. Estimated genetic correlations of birth weight with weaning grade and condition were consistently negative in sign. All correlations (genetic, environmental and phenotypic), except those thus far noted, were consistently positive. Correlated responses computed within sex indicated that birth weight might have some promise as an early selection criterion for improvement of weaning weight unless emphasis on birth weight should eventually lead to calving difficulties. For general application over sexes, direct selection remained a relatively promising method of increasing weaning weight. Responses of weaning grade and condition to selection for birth weight were negative. Responses of grade to selection for preweaning gain or weaning weight were inconsistent in sign between sexes. If direct selection to increase grade and condition is considered, then direct selection for only one of these two traits should be sufficient under the conditions of this experiment.

Footnotes

1 Arizona Agricultural Experiment Station Technical Paper No. 850. This study was conducted in cooperation with the USDA under Western Regional Project W-1, The Improvement of Beef Cattle through the Application of Breeding Methods. Cooperation of the Apache Indian Tribe of San Carlos, Arizona, by providing the essential livestock and facilities is gratefully acknowledged.

2 Beef Cattle Research Branch, Animal Husbandry Research Division, ARS, Denver, Colorado.






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Copyright © 1964 by the American Society of Animal Science.