J. Anim Sci.
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J. Anim Sci. 1984. 59:308-316.
© 1984 American Society of Animal Science
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Mathematical Modeling of Alternative Selection Strategies for Beef Production1

Stephen E. Clarke2,3,, C. T. Gaskins4, J. K. Hillers4 and W. D. Hohenboken2

Oregon State University, Corvallis 97331 and Washington State University, Pullman 99164-6310

Abstract

A closed beef herd of 500 cows and heifers was simulated over 40 yr. Several strategies for selecting bulls and cows were evaluated. Selection was practiced to increase weaning weight while holding birth weight constant. The bull-use strategy that maximized selection gains was to keep bulls for up to four breeding seasons (one season/year) while 75% of the 2-yr-old bulls were culled based on a progeny test of calves sired when the bulls were yearlings. Keeping bulls for two breeding seasons maximized genetic gains in weaning weight if progeny testing of sires was not practiced. Economic efficiency was maximized by keeping bulls for only one breeding season. Culling cows for not being pregnant or for not having a live calf at the end of the calving season improved economic efficiency to a greater degree than did decreasing the maximum cow replacement age or increasing the proportion of cows culled based on progeny performance, both of which also improved economic efficiency. Weaning weight was increased either by decreasing the maximum cow replacement age or by increasing the proportion of cows culled for poor progeny performance, but not by changing both simultaneously.

Footnotes

1 Technical Paper No. 6649, Oregon Agr. Exp. Sta. and Technical Paper No. 6431, Washington Agr. Exp. Sta. Contribution to Western Regional Coordinating Committee Project WRCC-1, "The Improvement of Beef Cattle through the Application of Breeding Methods."

Dept. of Anim. Sci., Oregon State Univ.

Current Address: Dept. of Anim. Sci., Colorado State Univ.

Dept. of Anim. Sci., Washington State Univ.






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