Effect of feeding wet distillers grains on performance, marbling deposition, and fatty acid content of beef from steers fed low- or high-forage diets.

One hundred thirty-eight Angus cross yearling steers (initial BW 390 ± 0.5 kg) were allotted by BW to a 3 × 2 factorial arrangement of 6 treatments (4 pens per treatment) to determine the effect of wet distillers grains (WDG) concentration (0, 20, 40% of dietary DM) in low-forage (12% hay) and high-forage (50% hay) diets on growth performance and marbling. Steers were implanted on d 0 with Component TE-S (VetLife, Overland Park, KS) and were slaughtered in 3 groups when final BW averaged 578 kg. Steers fed a low-forage diet gained BW faster (P < 0.001) than did steers fed a high-forage diet; the amount of WDG fed did not affect (P = 0.25) daily BW gain. Hot carcass weight and dressing percentage were greater (P < 0.001) for steers fed low-forage diets than for steers fed high-forage diets. Dressing percentage increased (P = 0.08) as WDG concentration increased. Longissimus muscle area (P = 0.08) and yield grade (P < 0.01) were greater for steers fed low-forage diets compared with steers fed high-forage diets. Longissimus muscle area (P = 0.02) and yield grade (P = 0.03) increased as WDG concentration increased. An interaction occurred for marbling (P < 0.01), fat thickness (P = 0.08), and PUFA content (P < 0.01). In steers fed low-forage diets, marbling score (325, 306, 265) and fat thickness (1.22, 1.07, 1.07 cm) decreased with WDG inclusion rates of 0, 20, and 40%, respectively, but in steers fed high-forage diets, marbling score (249, 282, 262) and fat thickness (0.89, 0.97, 0.81 cm) increased from the 0 to 20% inclusion rate and then decreased from the 20 to 40% inclusion rate. The inclusion of 0, 20, or 40% WDG increased PUFA content of beef from steers fed low-forage diets (6.9, 9.3, 10.6 g/100 g) but decreased PUFA content of beef from the 0 to 20% inclusion rate and then increased PUFA content of beef from the 20 to 40% inclusion rate in steers fed high-forage diets (8.5, 5.9, 7.8 g/100 g). In conclusion, when fed to a common BW end point, concentration of WDG in feedlot diets alters lean and adipose tissue deposition in beef cattle.