1673
Effect of wheat dried distillers grains with soubles inclusion and fibrolytic enzyme supplementation on ruminal fermentation and digestibility in beef heifers fed backgrounding diet
A metabolic study was conducted to evaluate the effects of wheat dried distillers grain with solubles (DDGS) inclusion and fibrolytic enzyme (FE) application on digestibility, ruminal pH and fermentation in beef heifers. Six ruminally cannulated Angus heifers (averaged BW 794 kg) were used in a 6 × 6 Latin square design with 2 × 3 factorial arrangement. Treatments were control (CON; 50% barley silage, 10% grass hay and 40% barley grain-based concentrate) and WDG (CON diet substituting 15% DDGS for barley grain) diets combined with 3 FE dosages (0, 1 and 2 mL FE/kg diet DM). Ruminal digestibility of wheat DDGS, barley silage and grass hay was measured using in situ technique and total digestibility was determined using Yb as external digesta marker. Heifers were fed at restriction of 90% ad libitum. Statistical analyses were conducted using the MIXED procedure of SAS with model including fixed effects of diet, FE and their interaction. In situ ruminal DM disappearance (DMD) of DDGS and grass hay did not differ between WDG and CON after 12, 24, or 48 h of incubation, whereas in situ ruminal DMD (34.0 vs. 36.9%; P = 0.01) of barley silage was greater in heifers fed WDG than CON after 24 h of incubation. Increasing FE application quadratically (P = 0.04) changed in situ DMD (61.1, 63.1 to 59.3%) of DDGS after 24 h of incubation and linearly (P = 0.03) increased in situ NDFD of barley silage (14.9 to 18.9%) after 24 h of incubation. There was no interaction between diet and FE dosages on total digestibility and ruminal pH and VFA concentration. Inclusion of DDGS increased the digestibility (CON vs. WDG) of CP (58.9 vs. 67.6%; P < 0.01), NDF (32.7 vs. 37.4%; P = 0.04) and ADF (25.0 vs. 31.0%; P = 0.03). Increasing FE linearly (P = 0.03) increased CP digestibility from 61.8, 63.5 to 64.5% without affecting the digestibility of other nutrients. There were no effects of DDGS inclusion and FE dosages on ruminal pH and VFA concentration except the concentration of propionate was greater (P = 0.04) with WDG (19.5 mM) than CON (18.5 mM). These results indicate that inclusion of wheat DDGS or supplementation of FE in barley silage-based background diet improved ruminal and total digestibility of NDF and CP, and had potential to improve feed efficiency in beef cattle.
Keywords: backgrounding beef heifers, fibrolytic enzyme, wheat distillers grain