405 WS Young Scholar Talk MS I: The impact of cow size on cow-calf and post-weaning progeny performance in the Nebraska Sandhills

Abstract

Abstract Optimizing beef production system efficiency requires an understanding of genetic potential suitable for a given production environment. Therefore, the objectives of this retrospective analysis were to determine the influence of cow body weight (BW) adjusted to a common body condition score (BCS) of 5 at weaning influenced cow-calf performance and post-weaning steer and heifer progeny performance. Data were collected at the Gudmundsen Sandhills Laboratory, Whitman, NE, on crossbred, mature cows (n = 1,715) from 2005 to 2017. Cow BCS at calving, pre-breeding, and weaning were positively associated (P < 0.01) with greater cow BW. Increasing cow BW was positively associated (P < 0.01) with the percent of cows that conceived during a 45-d breeding season. For every additional 100-kg increase in cow BW, calf BW increased (P < 0.01) at birth (2.70 kg) and adjusted 205-d weaning BW (14.76 kg). Calf pre-weaning average daily gain (ADG) increased (P < 0.01) 0.06 kg/d for every additional 100-kg increase in cow BW. Heifer progeny BW increased (P < 0.01) post-weaning with every addition 100-kg increase in dam BW. Dam BW did not influence (P ≥ 0.11) heifer puberty status prior to breeding, overall pregnancy rates, or the percent of heifers calving in the first 21-d of the calving season. Steer initial feedlot BW (7.20 kg¬), reimplant BW (10.47 kg), and final BW (10.29 kg) increased (P □ 0.01) for every additional 100-kg increase in dam BW. However, steer feedlot ADG was not influenced (P > 0.67) by dam BW. Hot carcass weights of steers were increased (6.48 kg; P = 0.01) with every additional 100-kg increase in cow BW. In a hypothetical model using the regression coefficients from this study, total output (calf weaning and cull cow BW) would be 6,352 kg greater utilizing a 454 kg cowherd compared with a 554 kg cowherd. Overall, larger sized-cows within this herd and production system of the current study had increased reproductive performance and offspring BW; however, total production output and economic returns would be potentially greater when utilizing smaller-sized cows.