377 Effects of corn silage inclusion rate in the finishing diet on performance, carcass characteristics, and liver abscess incidence of Holstein and Beef × Holstein steers.

Abstract The objectives were to investigate feedlot performance, carcass traits, and liver abscess incidence of Holstein (HO) and Beef × HO (B×HO) steers fed different corn silage inclusion rates in the finishing diet. After a 21-d adaptation, treatments were assigned in a 2x2 factorial arrangement, factors being breed type (HO or B×HO) and dietary inclusion of 20% or 40% corn silage (20CS or 40CS). Steers (n=120) were allocated to five pens per breed type by diet combination. Initial BW (266±18.7 kg) was included as a covariate for statistical analyses. Harvest occurred when treatments reached an average empty body fat (EBF) of 30% predicted by ultrasound. Carcass data were collected following a 48-h chill. The B×HO and HO steers were fed for 290 and 332-d, while 20CS and 40CS steers were fed for 307 and 314-d, respectively. There were no significant interactions between breed type and diet factors. The B×HO steers had a greater ADG, DMI, and gain:feed (P ≤ 0.01) compared with the HO steers. Dietary treatment did not affect performance metrics, except for DMI, which tended to be greater (P = 0.07) for steers fed 40CS than 20CS. Cost of gain was similar regardless of breed type and diet (P ≥ 0.68). Final live BW and hot carcass weight were greater for B×HO compared with HO (P ≤ 0.01) steers, but did not differ due to diet (P ≥ 0.19). Dressing percentage tended to be greater for B×HO compared with HO (P = 0.07) and was greater for steers fed 20CS compared with 40CS (P = 0.01). Liver abscess incidence was greater in HO compared with B×HO steers (49.2% vs. 21.7%; P < 0.01) and steers fed 20CS compared with 40CS (51.6% vs. 18.7%; P < 0.01). Additionally, B×HO carcasses had greater backfat thickness (P < 0.01) and greater longissimus muscle area (P < 0.01), but lesser kidney, pelvic, and heart fat percentage (P < 0.01), resulting in a lesser calculated USDA Yield Grade (P = 0.01) compared with HO carcasses. Carcass EBF, marbling score, and USDA Quality Grade were similar for breed type and diet (P ≥ 0.38). Carcass revenue was greater for B×HO carcasses when compared with HO carcasses (P = 0.04). Calculated breakeven value was $281/feeder calf greater for B×HO than HO (P = 0.02). Carcass revenue and breakeven feeder calf value were similar between diets (P ≥ 0.74). Overall, B×HO steers were more feed efficient, had a lesser incidence of liver abscesses, and produced carcasses with more desirable carcass yield, resulting in a greater breakeven feeder calf value compared with HO steers. Additionally, increasing corn silage inclusion from 20% to 40% reduced liver abscess incidence in both breed types without significantly influencing cost of gain.