Effects of increasing level of corn distillers dried grains with solubles on intake, digestion, and ruminal fermentation in steers fed seventy percent concentrate diets.J Anim Sci 2009; 87(9):2906-12JA
Five ruminally and duodenally cannulated steers (500 +/- 5 kg of initial BW) were used in a 5 x 5 Latin square to evaluate effects of increasing level of corn distillers dried grains with solubles (DDGS) in growing diets (70% concentrate) on OM intake, site of digestion, ruminal fermentation, and microbial efficiency. Diets consisted of 30% grass hay, 6% concentrated separator by-product, 4% supplement, and 60% dry-rolled corn, sunflower meal, urea, or DDGS (DM basis). Treatments consisted of increasing DDGS at 0, 15, 30, 45, or 60% of diet DM replacing a combination of dry-rolled corn, sunflower meal, and urea. Diets were balanced for growing steers gaining 1.22 kg/d and included 0.25% (DM basis) chromic oxide as a digesta flow marker. Diets were offered to the steers for ad libitum intake each day (10% above the intake of the previous day). Each period consisted of 14 d for adaptation and 7 d for collections. Intake of OM responded quadratically (P = 0.004) with greatest intakes at 15% DDGS and least at 60% DDGS. No differences (P >or= 0.14) were observed in CP intake or duodenal flow of OM, CP, and NDF. Apparent and true ruminal OM digestibilities decreased (linear; P <or= 0.009) with increasing DDGS inclusion. Total tract CP digestibility increased (linear; P < 0.001) with increasing DDGS, but total tract OM digestibility was not different (P = 0.74). Microbial efficiency (g of microbial N/kg of OM truly fermented) was not affected (P = 0.22) by treatment. As DDGS increased, ruminal pH increased (linear; P = 0.004), whereas ammonia concentration remained unchanged (P = 0.42). Acetate proportions decreased (linear; P < 0.001) with increasing DDGS, whereas propionate and butyrate were not affected (P >or= 0.19). A cubic (P = 0.02) effect was observed for total ruminal fill (as is basis) with the greatest fill at 0% DDGS and the least fill at 45% inclusion. Replacing dry-rolled corn with up to 60% DDGS in 70% concentrate diets resulted in no adverse effects on total tract OM digestion, although OM intake was reduced at 60% DDGS inclusion.