J.P. Schoonmaker, F.L. Fluharty, S.C.
Loerch1, and T.B. Turner
The Ohio State University Department of Animal Sciences
Abstract
Seventy Angus X Simmental crossbred calves (initial body weight (BW) 366.5 ± 9.3 lb) were used in a 3 X 2 factorial arrangement of treatments to determine the effect of age at feedlot entry and castration on growth, performance, and carcass characteristics. At 82 days of age (5-26-99), calves in the steer group were castrated. Calves were placed in the feedlot at 110 days of age (EW), 202 days of age (NW), or 371 days of age (Y). Calves in the NW and Y group remained with their dams until 188 days of age, and consumed pasture until feedlot entry (202 and 371 days of age; respectively). Steers were implanted with Synovex-S (when steers were 93 days from their terminal implant), and with Revalor-S (when steers were estimated to be 100 days from slaughter). Calves were slaughtered on an individual basis when backfat was estimated to be 0.5 inches. While in the feedlot, Y calves gained faster (P < 0.01) than NW and EW calves (4.15, 3.71, and 3.57 lb/day); however, when measured from 110 days of age until slaughter, average daily gain (ADG) was greatest for EW, intermediate for NW, and lowest for Y calves (3.57, 3.25, and 2.67 lb/day; P < 0.01). Early-weaned calves spent the most days in the feedlot, followed by NW, and Y calves spent the fewest days in the feedlot (221, 190, and 163 days; P < 0.01). Total dry matter intake (DMI) was similar (P > 0.22) between age groups; however, daily DMI was the lowest for EW, intermediate for NW, and the highest for Y calves (15.7, 17.9, and 23.1 lb/day; P < 0.01). Early-weaned calves were the most efficient, followed by NW, and Y calves were the least efficient (0.227, 0.207, 0.180 lb gain/lb feed; P < 0.01). Weight at slaughter (1504, 1284, and 1141 lb; P < 0.01) and hot carcass weight (911, 789, and 693 lb; P < 0.01) was greatest for Y calves, intermediate for NW, and lowest for EW. Early-weaned calves had the smallest rib-eye area, followed by NW, and Y had the largest rib-eye area (12, 13, and 14 in2; P < 0.01). Early-weaned and NW calves had lower yield grades (3.2, 3.1, and 3.5; P < 0.04) and produced fewer select carcasses compared to Y calves (25, 13, and 48 %; P < 0.01). Bulls and steers both had an average daily gain of 3.8 lb/day while in the feedlot; however, bulls had a greater (P < 0.09) hot carcass weight (816 versus 780 lb) and a larger (P < 0.01) rib-eye area (13.3 versus 12.6 in2) compared to steers. Earlier feedlot placement results in higher quality beef.