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The influence of dry-rolled corn particle size and dried corn distiller's grains plus solubles inclusion levels on digestibility in steers
Eight cannulated Holstein steers (525 ± 3.6 kg) were used in a 4 × 4 Latin square experiment to examine the impact of fine- vs. coarse-rolled corn and 20 vs. 40 % dried distiller's grain with solubles (DDGS) inclusion on nutrient digestibility. Animals were housed in individual stalls in a temperature-controlled room. Dietary treatments consisted of 1) 65% coarse-rolled corn (2.5 mm) and 20% DDGS, 2) 45% coarse-rolled corn and 40% DDGS, 3) 65% fine-rolled corn (1.7 mm) and 20% DDGS and 4) 45% fine-rolled corn and 40 % DDGS. Treatments were offered to ensure ad libitum intake and approximately 6 % feed refusal daily. Chromic oxide was added to each ration at 0.25 % as an external marker. Steers were provided experimental diets for a period of 14 d, and daily feed intake and fecal excretion was recorded during the final 7 d. Intake, excretion and disappearance of DM, OM, CP, NDF and ADF were measured. Results were analyzed using the Mixed procedure of SAS. No differences were observed between treatments for intake or disappearance of DM or OM (P ≥ 0.24). Intake, duodenal flow, and total tract disappearance of CP were greater (P ≤ 0.04) in steers consuming 40% DDGS. Crude protein ileal flow and rumen microbial efficiency (microbial CP produced/OM fermented) were not influenced by treatment. Starch intake, fecal output and total tract disappearance were greater (P ≤ 0.01) in rations with 20% DDGS while no impact was observed for duodenal and ileal flow. Feeding coarse-rolled corn increased (P = 0.02) NDF digestibility (% of intake) while feeding 40% DDGS increased (P ≤ 0.01) NDF intake, fecal output, and total tact disappearance. An interaction between corn and DDGS was observed (P ≤ 0.05) for NDF total tract disappearance, apparent ruminal digestibility, and total tract digestibility with greater values present in treatments containing coarse-rolled corn and 20% DDGS. Intake, total tract disappearance, and total tract digestibility of ADF was greater (P ≤ 0.001) in diets containing 40% DDGS. Duodenal flow and ileal flow of NDF and ADF were unaffected by treatment (P ≥ 0.06). Results of this study indicate that increased corn grain inclusion rates have a greater impact on total tract disappearance of starch while CP and fiber disappearance and digestibility are more likely to be affected by increased DDGS.
Keywords: bovine, corn, distillers, nutrient disappearance