INTERBREED EVALUATION OF BEEF CATTLE PRODUCTIVITY UNDER LOW AND MODERATE DRY MATTER AVAILABILITIES

Costs limit live animal experimentation to quantify genotype by environment interactions in herd productivity due to the number of production environments and beef cattle germ plasm combinations. Life cycle simulation models enable producers to evaluate breeds differing in genetic potential for productivity under a variety of environmental conditions; e.g., inter- or intra-breed by environment interactions. A simulation model developed for within ranch evaluations, DECI, was parameterized to evaluated productivity for a constant calving population inventory herd of two biological types of beef cattle across two production environments differing only in annual yields of dry matter (DM), low and moderate. The two biological types evaluated differed in genetic potentials for mature size and peak milk yield with each type having associated attributes; e.g., propensity to fatten, measures of fertility, dystocia and maintenance requirements. Ranking for weight of calf marketed per cow exposed of the two biological types differed depended on environment. Under restrictive DM the biological type with greater genetic potential for growth and milk production marketed fewer kilograms of product per cow exposed. At moderate DM availability, the biological type with greater genetic potential yielded more of this product. Application of dynamic simulation models provides an opportunity to investigate genotype by environment interactions