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Mathematical Modeling of Alternative Culling and Crossbreeding Strategies in Beef Production¹

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

Abstract

A 500-head, spring-calving, cow-calf enterprise was modeled in which the number of cows in the calving herd was held constant. The study was designed to evaluate the relative economic efficiency of (1) three mating plans (three-breed rotational, three-breed terminal and combination two-breed rotational, to produce female replacements, with terminal, called the criss-out-cross system) when terminal sire breeds of several sizes were used, (2) mandatory cow replacement ages between 5 and 16 yr and (3) cow culling strategies based on measures of reproductive failure (not pregnant, no live calf at the end of the calving season or failure to wean a calf). Replacing nonpregnant cows in the fall with a heifer increased economic efficiency, as did replacing cows without a live calf at the end of the spring calving season. Replacing cows for failure to wean a calf decreased economic efficiency. The use of a very large terminal breed in the criss-out-cross or three-breed terminal cross sytems surpassed the three-breed rotational cross system in economic efficiency. The criss-out-cross system was superior to the three-breed terminal cross at cow replacement ages less than 12 yr. The cow replacement ages that maximized gross margin/ cow were 5, 9 and 12 yr for three-breed rotational, criss-out-cross and three-breed terminal crossbreeding, respectively. This reflected the average utilization of individual and maternal heterosis for the various mating plans.

¹ Technical Paper No. 6561, Oregon Agr. Exp. Sta. and Technical Paper No. 6365, Washington Agr. Exp. Sta. Contribution to Western Regional Coordinating Committee WRCC-1, "The Improvement of Beef Cattle through the Application of Breeding Methods."

² Dept. of Anim. Sci., Oregon State Univ.

³ Current address: Dept. of Anim. Sci., Colorado State Univ., Fort Collins 80521.

⁴ Dept. of Animal Sci., Washington State Univ.