Effect of weaning status and implant regimen on growth, performance, and carcass characteristics of steers

One hundred forty-three Angus x Simmental crossbred steers (initial BW = 15 5.1 +/- 4.5 kg) were used in a 2-yr study (yr 1, n = 67; yr 2, n = 76) to d etermine the effects of weaning age, implant regimen, and the weaning age x implant regimen interaction on steer growth and performance, organ mass, c arcass characteristics, and cooked beef palatability. Steers were early-wea ned at an average age of 108 d (EW) or normally weaned at an average age of 202 d (NW) and allotted by weight to an aggressive or nonaggressive implan t regimen. On their respective weaning dates, EW and NW steers were penned individually and fed a grain-based diet until they were slaughtered at a fi nal BW of 546 kg. A subsample of steers (n = 2 per treatment) were slaughte red at 254 kg. At 254 kg, EW steers implanted with the aggressive implant r egimen had 64% greater backfat depth than those implanted with the nonaggre ssive implant regimen; conversely, NW steers implanted with the aggressive implant regimen had 52% lower backfat depth than those implanted with the n onaggressive implant regimen (weaning status:x(implant regimen interaction; P < 0.01). A similar interaction was observed for empty visceral organ wei ghts. Early-weaned steers were younger (354.7 vs 372.4 d; P < 0.01) at; fin al slaughter but were in the feedlot longer (246.5 vs 169.6 d; P < 0.01) th an NW steers, whereas the aggressive implant regimen decreased days fed (20 3.3 vs 212.7; P < 0.07) compared to the nonaggressive implant regimen. Over all ADG was greater for EW than for NW steers (1.61 vs 1.50 kg/d; P < 0.01) and for the aggressive compared with the nonaggressive implant regimen (1. 59 vs 1.52 kg/d; P < 0.02). Early-weaned steers consumed less DM per day (7 .4 vs 8.5 kg/d; P < 0.01) and were more efficient (0.217 vs 0.208 kg/kg; P < 0.02) but consumed more total DM (1,817 vs 1,429 kg; P < 0.01) than NW st eers while in the feedlot. Implant regimen did not affect DMI (P > 0.37) or feed efficiency (P > 0.15). Weaning status did not affect carcass characte ristics (P > 0.14), final empty body composition (P > 0.25), or final longi ssimus muscle composition (P > 0.18); however, steaks from EW steers had hi gher (P < 0.05) taste panel tenderness and juiciness ratings than steaks fr om NW steers. The aggressive implant regimen decreased yield grade (P <less than> 0.02), but did not affect; quality grade (P > 0.86) compared to the nonaggressive implant regimen. Placing early-weaned steers on an aggressive implant regimen is a viable management option.