INTEGRATED BEEF PRODUCTION MODELS FOR CROSSBREEDING STUDIES: COMPARISON OF DIFFERENT MANAGEMENT PROGRAMS

The effects of three management programs on each of three mating types, each at two levels of reproductive performance, have been investigated using a linear programming (LP) model. Data were for straightbred bulls bred to smaller two-breed cross cows, with sizes L♀ × SS♂, L♀ × MM♂ and M♀ × SS♂, where L, M and S were 800, 600 and 400 kg, respectively. Two-breed crossbred replacement heifers for the breeding herd were considered as a purchase item, and with this exception the model was integrated, in the feeding to slaughter weight of three-breed terminal cross calves from two-breed cross cows, and with cow and calf requirements for land, cropping, labor and capital. The three management programs involved methods of purchasing replacement breeding heifers: at 7 mo (T7) or 19 mo (T19)of age, or at 7 mo with disposal of the same number of terminal cross calves of the same age (TM), a modification to provide direct comparison with a rotation crossing system. On the basis of farm gross margins and the TM program, mating types ranked in the order L × SS, L × MM and M × SS (largest to smallest). On the average, one percentage point increase in calf crop percentage gave an extra 2.42 kg of saleable beef and $1.54 increased gross margins per cow. Assessing the T7 and T19 programs on the basis of farm gross margins, the L × MM and L × SS mating types were reranked, but the effects of reproductive performance were not consistent for the T7 and T19 programs. Optimal herd sizes, annual herd yields of beef, beef output/cow, gross margins/cow, total money returns/cow, costs/cow and costs/kg beef were also analyzed for each program.