100 Young Scholar Presentation: Energy and Mineral Supplementation Strategies for Beef Cattle Grazing the Northern Great Plains

Three experiments were conducted to evaluate supplementation strategies for beef cattle grazing in the Northern Great Plains. In experiment 1, 28 cow-calf pairs had access to electronic feeders (SmartFeed system; C-Lock Inc., Rapid City, SD) that monitored individual vitamin and mineral supplement (VTM) intake. Cows had greater VTM intakes (81.1 ± 8.2 g/d; P < 0.01) than calves (44.2 ± 8.6 g/d) but both attended feeders a similar (P = 0.71) proportion of days. Furthermore, we noted greater (P < 0.01) concentrations of Se, Cu, and Co in livers of HIGH intake cows compared to LOW intake cows. Experiment 2, we used the SmartFeed system to regulate intake of individual heifers (n = 60) in a group pasture scenario assigned to control (CON), VTM, or energy supplement (NRG) treatments, and evaluated supplement intake, and concentrations of liver mineral and metabolites. Though no differences were observed in BW and ADG, treatments that provided VTM enhanced liver concentrations of Se, Fe, Cu, and Co (P < 0.05). No differences (P = 0.85) were observed in concentrations of NEFA; however, NRG heifers had greater (P = 0.01) glucose concentrations than CON and VTM heifers. Experiment 3 objectives were to determine the influence of feeding VTM and NRG supplements to beef heifers (n = 35) during the first 84 days of pregnancy on concentrations of progesterone (P4), corpus luteum (CL) size and fetal body measurements. Providing NRG during early gestation resulted in heavier CLs (P = 0.003) that produced more P4 (P = 0.002) and greater fetal femur growth (P = 0.009) whereas providing VTM enhanced fetal liver growth (P = 0.05). Overall, we were able to successfully monitor and control individual mineral intake, corroborated those differences in liver mineral concentrations, and observed alterations in fetal growth after mineral and energy supplementation.