ANIMAL PRODUCTION PROJECT SUMMARY
Our overarching goal is to develop strategies and technologies for reducing costs of beef production, including enhanced efficiency of nutrient utilization and improved reproductive performance. Feed intake levels resulting in adequate body energy stores are widely believed essential for successful reproduction. Feed consumption and replacement of cows culled for reproductive failure are two primary determinants of cost of beef production. Producers seek to optimally match nutritional environment and genotype to obtain high rates of reproduction. This optimization is complicated by the symbiotic interplay between host animal and rumen microbial populations. Our approach is of necessity long-term and multi-disciplinary, involving genetics, physiology, nutrition, and microbial metagenomics. This proposal brings to fruition ongoing research and establishes new lines of investigation. Four distinct cattle populations are used: Line 1 Hereford, an intercross (CGC) of Charolais (25%), Red Angus (50%) and Tarentaise (25%), and two predominantly Hereford-Angus crossbred herds. Line 1 Hereford cattle are ~30% inbred, with consequently reduced fitness, and have close ties to the bovine genome sequence and the general US Hereford population. These characteristics facilitate assessing genetic factors affecting fitness and assure relevance to the industry. Two distinct nutritional environments will be imposed on the CGC population to challenge the nutrition-reproduction interrelationship. One Hereford-Angus cowherd provides donor and recipient females for studies using embryo transfer. The other Hereford-Angus cowherd calves in two distinct timeframes and thus has differential synchrony between nutritional value of range forage and nutrient requirements of the cows. To address a broad spectrum of customer interests, we envision a mixture of basic investigations and applied studies.
USDA, ARS Fort Keogh Livestock and Range Research Laboratory