Evaluation of Crossbreeding Systems for Small Beef Herds: I. Single-Sire Systems

Abstract

Stochastic computer models were developed to evaluate crossbreeding systems in small beef herds consisting of one bull, 30 cows and 10 replacements. Six systems were simulated: purebred (PB), two- and three-breed rotations using one bull per year (2R and 3R) or artificial insemination (2RAI and 3RAI) and four-breed composite (COMP). Inbreeding was avoided in all systems. Female replacements were selected from within the herd, whereas sires were purchased. Average heterosis estimates were assumed for calf survival (4.0%), conception rate (6.6%), weaning weight (5.4%, individual; 4.7%, maternal) and mature weight (2.5%). Estimates of calf and dam heterosis were used to calculate performance for calf weights weaned and sold, cull cow weights sold, total weight sold and gross calf, cow and total income. All crossbred systems were superior to the purebred system for weights sold and total income. The 2R and 3R systems utilized 82 to 85% of maximum heterosis available in 2RAI and 3RAI systems, respectively; however, no significant losses were found in weights sold or gross incomes. The COMP system ranked higher than 2R and 2RAI systems for all traits. Increasing the number of breeds (2 vs 3) did not significantly increase total weights or gross incomes. Results demonstrated that practical crossbreeding can be managed easily in small herds and that matings resulting in suboptimal heterosis levels do not cause significant losses in gross income.