Effect of degradable intake protein supplementation in finishing diets containing dried distillers grains or wet distillers grains plus solubles on performance and carcass characteristics1

Two finishing trials were conducted to determine whether supplemental degradable intake protein is necessary to optimize performance in dry-rolled corn (DRC) based finishing diets containing distillers grains. Diets without urea were deficient in degradable intake protein based on the NRC (1996) recommendations, yet all diets had positive metabolizable protein balances. In Exp. 1, individually fed, crossbred heifers (n = 58; BW = 383 ± 25 kg) were used in a completely randomized design with a 2 × 2 factorial arrangement of treatments. Dietary treatments contained 10 or 20% dried distillers grains replacing DRC, with or without 0.80 or 0.63% urea, respectively (DM basis). Blood samples were analyzed for BUN. Heifers receiving urea or 20% dried distillers grains (P < 0.01) had greater BUN concentration than did heifers not receiving urea or fed 10% dried distillers grains, respectively. In Exp. 2, pen-fed, crossbred steers (n = 336; initial BW = 365 ± 31 kg) were assigned randomly within block to 1 of 24 pens in a randomized complete block design with 3 treatments. Dietary treatments were 0, 0.5, or 1.0% urea added to a DRC diet containing 25% wet distillers grains plus solubles (DM basis). Marbling tended to decrease linearly (P = 0.09) as urea level increased. However, no other significant differences (P > 0.10) were observed for performance or carcass characteristics for either experiment. These data indicate supply of ruminal degradable intake protein was adequate to maintain performance when at least 10% distillers grains was included in DRC diets.