Abstract #2

# 2
Beef heifer development systems and lifetime productivity.
Andrew J. Roberts*1, Rick N. Funston2, Elaine E. Grings3, Mark K. Petersen1, 1USDA-ARS, Fort Keogh LARRL, Miles City, MT, 2University of Nebraska West Central Research and Extension Center, North Platte, NE, 3Department of Animal Science, South Dakota State University, Brookings, SD.

Research continues to amass proving nutrition and other environmental factors experienced during pregnancy affect the fetus, resulting in changes in traits exhibited through life. In livestock, small differences in nutritional profiles during gestation may result in fetal programing that alters lifetime production efficiency. Thus, the potential of fetal programing should be considered when determining supplemental feeding strategies during gestation. For example, evaluation of offspring born to cows grazing dormant pasture supplemented with either 1.1 or 1.8 kg/d of alfalfa hay during the last 3rd of gestation demonstrated females born to cows provided the lower supplementation level were 10 kg heavier and had greater BCS at 5 yr of age. These differences appeared beneficial for maintaining reproductive performance in offspring managed with less harvested feed inputs. Comparison of offspring from cows wintered on native range (low quality) or improved pasture (greater quality) for 30 to 45 d during the 5th to 6th mo of gestation resulted in a trend for longer productivity in daughters from cows wintered on improved pasture. In recent studies comparing offspring from cows with or without protein supplementation while grazing dormant winter range during late gestation, heifers from protein-supplemented dams had greater BW at weaning. This increase in BW persisted through pregnancy diagnosis and subsequent calving, and pregnancy rates were greater in heifers from protein-supplemented dams. Heifers from protein-supplemented dams appeared less feed efficient compared with heifers from un-supplemented dams. Thus, in utero exposure to nutritionally restricted environments (non-supplemented dams) may promote greater feed efficiency later in life. Nutrition during post-weaning development may also affect lifetime productivity. Heifers developed on low quality native range with RUP supplementation had greater retention beyond 3 yr of age than cohorts developed in a feed lot with higher quality feed and greater ADG. Collectively, these examples show long-term effects of nutritional management strategies used during gestation and development in given production environments need to be evaluated.

Key Words: fetal programing, lifetime productivity, nutritional supplementation

Speaker Bio
Andy has been involved in beef cattle research since 1982, which has resulted in over 90 technical and scientific publications, including 49 in refereed journals, and 58 invited presentations at scientific or producer meetings. Research has focused on identifying basic mechanisms regulating reproduction in cattle in order to develop methods and management approaches that improve reproductive efficiency. Goal of basic research at Ft Keogh is to identify genes and physiological traits associated with enhanced production efficiency under sustainable nutritional regimens. Traits of economic importance being evaluated include growth, feed intake, ultrasound carcass characteristics and age of puberty in heifers and bulls; and re-breeding reproductive success, body weight and condition, weight of calf at weaning and longevity of production in cows. Results from research will provide opportunities to improve efficiency of beef cattle production by developing methods that minimize animal input requirements and enhance lifetime production characteristics.