Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/24/2013
Publication Date: 7/1/2013
Publication URL: http://handle.nal.usda.gov/10113/56940
Citation: Hales, K.E., Freetly, H.C., Shackelford, S.D., King, D.A. 2013. Effects of roughage concentration in dry-rolled corn-based diets containing wet distillers grains with solubles on performance and carcass characteristics of finishing beef steers. Journal of Animal Science. 91(7):3315-3321. Interpretive Summary: Distillers grains are by-products of grain fermentation used to produce ethanol and contain relatively high amounts of fiber compared with the grains and concentrates they replace in feedlot diets. Typical finishing diets in the U.S. contain between 8.0 and 9.0% roughage. Therefore, it is possible that the concentration of roughage in a feedlot diet can be decreased when distillers grains are included in the diet. An experiment was conducted to evaluate the effects of roughage concentration in diets based on dry-rolled corn with wet distillers grains and solubles. One-hundred and twenty-eight fall-born steers were used. Individual feed intake was recorded daily and BW was measured every 35 days. Decreasing roughage in the finishing diet increased average daily gain at lower concentrations of roughage and decreased average daily gain at higher concentrations of roughage in the diet. Dry matter intake was less when lower concentrations of roughage were fed in the diet, and feed efficiency was greater when roughage concentration was low. Roughage concentration had no effect on carcass characteristics. Therefore, roughage concentration can be decreased in finishing cattle diets without adversely affecting cattle performance or carcass quality.
Technical Abstract: Distillers grains and distillers solubles are by-products of grain fermentation used to produce ethanol and contain greater concentrations of NDF and ADF compared with other grains and concentrates they replace in feedlot diets. Typical finishing diets in the U.S. contain 8.3 and 9.0% roughage. Therefore, it is plausible that the dietary concentration of roughage can be altered when distillers grains are included in feedlot diets. The effects of roughage concentration in dry-rolled corn-based diets containing wet distillers grains with solubles (WDGS) were evaluated in steers (n = 128, initial BW = 339 kg) using Calan gates. Each diet was based on dry-rolled corn and contained 25% WDGS with coarsely ground alfalfa hay (AH) replacing corn at 2% (AH-2), 6% (AH-6), 10% (AH-10), and 14% (AH-14) of DM. Feed offered was recorded daily, orts were measured weekly, and BW was measured on d 0, 1, 35, 70, 105, 140, 174, and 175. Following commercial harvest and chilling, carcasses were evaluated on-line with a beef carcass grading camera to assess marbling and yield grade traits. The data were analyzed using the Mixed procedure of SAS in which contrast statements were used to separate linear and quadratic effects of AH inclusion. Decreasing concentrations of AH in the finishing diet resulted in a tendency for a quadratic response (P = 0.07) in final BW where BW increased from 2 to 6% AH inclusion but then decreased from 6 to 14% inclusion. Similiarly, ADG from d 0 to end responded quadratically (P < 0.01) in which ADG increased from 2 to 6% yet subsequently decreased from 6 to 14% AH inclusion. Dry matter intake from d 0 to end increased linearly (P = 0.02) as AH inclusion increased in the diet; whereas, G:F increased from 2 to 6% AH inclusion and then decreased linearly (P < 0.01) from 6 to 14% AH inclusion. Concentration of AH in the finishing diet did not affect HCW, marbling score, or the proportion of cattle grading USDA choice (P > 0.18). However, dressing percent and LM area did respond in a quadratic manner (P < 0.02) in which they decreased from 2 to 10% AH inclusion and increased from 10 to 14% AH in the diet. Yield grade and adjusted 12th rib fat responded quadratically (P > 0.01) in which both increased from 2 to 6% AH inclusion and decreased from 6 to 14% inclusion. Analysis of responses of G:F and ADG on AH predict the apex at 3 and 7% for G:F and ADG, respectively, when fed in diets containing 25% WDGS.