Effects of wet corn distiller's grains with solubles and nonprotein nitrogen on feeding efficiency, growth performance, carcass characteristics, and nutrient losses of yearling steers

Authors: PONCE, CHRISTIAN - West Texas A & M University; COLE, N. ANDY - Retired ARS Employee; SAWYER, JASON - Texas A&M University; DA SILVA, JULIO - West Texas A & M University; SMITH, DOUG - West Texas A & M University; MAXWELL, CASEY - West Texas A & M University; BROWN, MIKE - Elanco Animal Health, Inc

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2019
Publication Date: 4/15/2019
Citation: Ponce, C., Cole, N., Sawyer, J., Da Silva, J., Smith, D., Maxwell, C., Brown, M.S. 2019. Effects of wet corn distiller's grains with solubles and nonprotein nitrogen on feeding efficiency, growth performance, carcass characteristics, and nutrient losses of yearling steers. Journal of Animal Science. 97(6):2609-2630. https://doi.org/10.1093/jas/skz133.
DOI: https://doi.org/10.1093/jas/skz133

Interpretive Summary: American feedlots require cost effective feed ingredients to produce beef products competitively. Wet distiller’s grains with solubles (WDGS) are a common by-product feedstuff generated by the grain-ethanol industry, and can be used as a cost effective feed ingredient. The protein in WDGS has low digestibility in the cow’s first stomach, the rumen, and thus, the quantity of protein that is consumed in the rumen may be deficient. The easiest way to increase the degradable protein in the rumen is to add urea. Therefore, scientists from ARS (Bushland, Texas), Texas A&M AgriLife Research and West Texas A&M University conducted two feeding studies to evaluate the supplemental ruminal protein requirements of beef cattle fed steam-flaked corn-based feedlot diets with 0 to 30% WDGS. Based on average daily gain, no supplemental urea was required in diets that contained 30% WDGS. However, increasing urea was needed as the percentage of WDGS in the diet was decreased. These results are of interest to feedlot operators because they define optimal levels of protein supplementation with varying amounts of WDGS in the diet.

Technical Abstract: Wet distiller’s grains with solubles (WDGS) is a common by-product feedstuff generated by the grain-ethanol industry, and it is used extensively by the cattle feeding industry. Distiller’s grains are typically high in protein; however, the protein in WDGS has a low ruminal degradability, and thus may result in a deficiency of rumen degradable protein (RDP) in the diet even when dietary crude protein (CP) concentrations are high. Assessment of the RDP needs in diets containing WDGS is needed to aid the cattle feeding industry in managing feed costs and potential environmental issues. To that end, we conducted two feeding studies to evaluate the supplemental RDP requirements of beef cattle fed steam-flaked corn-based finishing diets. In experiment 1, 525 yearling steers (initial body weight = 373 ±13 kg) received treatments in a 2 × 3 + 1 factorial. Dietary factors included WDGS (15 or 30% of dry matter [DM]) and non-protein N (NPN; 0, 1.5, or 3.0% of DM) from urea. The control diet without WDGS contained 3.0% NPN (1.06% urea) and cottonseed meal. Diets were formulated to have equal crude fat concentrations. Overall gain efficiency among steers fed 15% WDGS was greatest for 1.5% NPN and least for 0% NPN (P = 0.07, quadratic); whereas, gain efficiency decreased linearly (P < 0.09) as NPN increased in the 30% WDGS diets. Dressing percent was greater (P < 0.01) for the Control diet than for 15% or 30% WDGS. In experiment 2, 296 steer calves (initial BW = 344 ± 12 kg) were fed one of four experimental diets that included a Control diet without WDGS (contained 3% NPN from urea, and cottonseed meal) and 15% WDGS diets with either 1.50, 2.25, or 3.00% NPN (0.52, 0.78, and 1.04% urea, respectively, on a DM basis). Overall gain efficiency on either a live or carcass-adjusted basis was not different among treatments (P > 0.15). Dietary NPN concentration did not influence growth performance (P > 0.21). Increasing dietary WDGS concentration resulted in decreasing diet digestibility and increasing N volatilization losses; however, the effects of NPN level on digestibility and N losses was somewhat inconsistent across experiments. Results suggest that optimum performance for cattle fed 15% WDGS occurred when the diet contained between 1.5% and 2.25% NPN. However, no supplemental NPN was needed to support optimum performance in diets containing 30% WDGS.