PS5-26. Evaluation of Maternal Supplementation of Choline on Progeny Growth Performance During the Finishing Period and Carcass Characteristics.

Abstract Previous research has demonstrated that prepartum supplementation of dairy cows with rumen-protected choline (RPC) can improve calf health, increase growth performance during the finishing phase, and improve marbling score in beef ´ dairy calves. To evaluate the effects of maternal supplementation with RPC in beef cows and their offspring, pregnant Angus cows (n = 80) were fed during the prepartum period (target 45 days) with a total mix ration containing: A) 12.9 g/cow daily of rumen protected choline ion (RPC; 60 g of ReaShure®, Balchem Corp.; 21.5% choline ion content) or B) 0 g/cow daily RPC (CTL). Following a backgrounding period, a subset of 17 bulls were banded 84 d prior to the feedlot phase and were finished at South Dakota State University Cow-Calf Education and Research Facility (CCERF; Brookings, SD). Individual feed intake of steers was measured for 107 days in a Monoslope barn equipped with electronic feeders (Insentec, The Hague, Netherlands). The finishing diet was based on dry-rolled corn and provided 1.39 Mcal/kg NEg. Data were analyzed using mixed models with the fixed effect of maternal treatment and random effect of animal. Differences were declared as significant at P ≤ 0.10, and tendencies at 0.10 < P ≤ 0.15. At initiation of the finishing period, steers born from RPC-supplemented dams weighed 566 kg, compared with the 504 kg of BW of steers from CTL-dams (P = 0.07). This effect was maintained until day 70 on feed, when RPC-derived steers weighed 705 kg compared with the 640 kg of CTL-derived steers (P = 0.07). At 107 days of feed, final BW (FBW) tended to differ between groups (P = 0.14; 685 kg vs 736 kg ± 22.3 kg for CTL vs RPC, respectively). Hot carcass weight (HCW) tended to differ between groups (P = 0.13; 435 kg vs 470 kg ± 15.5 kg for CTL vs RPC, respectively). Cumulatively, no differences were observed between groups for average daily gain (P = 0.57; average 1.92 kg), dry matter intake (P = 0.31; average 13.6 kg), or gain to feed (P = 0.23; average 0.141 kg/kg). Yield grade tended to be greater for the RPC-derived steers (P = 0.10; 3.45 vs 3.86, for RPC vs CTL, respectively). No other differences in carcass characteristics were observed (P ≥ 0.47) for ribeye area, rib fat, marbling, dressing percentage, and empty body fat. Differences in FBW and HCW for RPC could have meaningful economic impacts. Following backgrounding, steers from RPC-supplemented dams had a weight advantage; however, during finishing, the initial BW difference did not translate into enhanced growth performance or carcass characteristics. Further research is needed in larger cohorts to determine if maternal supplementation of RPC will have impacts on finishing period growth performance and carcass characteristics.