Project Number: 5434-31000-017-00
Start Date: Oct 23, 2012
End Date: Oct 22, 2017
Feed consumption and replacement of cows, culled for reproductive failure, are two primary determinants of beef production efficiency. Our overarching goal is to develop strategies and technologies to alleviate these limitations. Sufficient nutrient intake resulting in adequate body energy stores are believed essential for reproduction. Thus, producers are challenged to match nutritional environment, which is subject to seasonal and annual variation, and various genotypes to obtain sustainable reproduction and retention rates. Our approach is, of necessity, long-term and multi-disciplinary, involving both basic and applied aspects of genetics, nutrition, and physiology in a semi-arid grazing production system. This proposal brings to fruition ongoing research and establishes investigations of genetic by environmental interactions and physiological mechanisms limiting reproductive success. Four distinct cattle populations (an intercross of Charolais (25%), Red Angus (50%) and Tarentaise (25%), Line 1 Hereford, purebred Angus, and Hereford-Angus herd) will be used to facilitate assessment of genetic factors affecting fitness (hybrid vigor). Distinct nutritional environments that utilize different contributions of harvested and grazed forage will be imposed to challenge the nutrition-reproduction interface to elucidate genetic, physiological, and management factors influencing feed utilization and lifetime productivity. Identification of genetic, nutritional, and physiological mechanisms that limit or contribute to beef production efficiency will facilitate early in life selection and management of replacement animals most fit for particular production environments. This research will result in the establishment of heifer development protocols that provide producers options for dealing with annual variations in availability and quality of forage.