Effects of increasing levels of corn distillers dried grains with solubles to steers offered moderate-quality forage

Supplementation of forage-fed livestock has been studied for decades; however, as by-products become available research is needed to determine optimal feeding rates for increased efficiency. Five ruminally and duodenally cannulated beef steers (446 +/- 42 kg of initial BW) were used in a 5 x 5 Latin square to evaluate effects of increasing level of supplemental corn distillers dried grains with solubles (DDGS; 25.4% CP, 9.8% fat, DM basis) on DMI, rate and site of digestion, ruminal fermentation, and microbial efficiency. Diets consisted of ad libitum quantities of moderate-quality smooth brome hay (10.6% CP; DM basis), free access to water and trace mineral salt block, and 1 of 5 levels of DDGS (0, 0.3, 0.6, 0.9, and 1.2% of BW daily of DDGS; DM basis). Diets were formulated to meet or exceed the estimated rumen degradable protein requirements (assumed microbial yield = 10.5%). All supplements were fed at 0600 h before forage was fed. Steers were adapted to diets for 14 d followed by a 7-d collection period. Hay OM intake decreased (linear; P < 0.001), whereas total OM intake increased (linear; P < 0.001) with increasing DDGS level. Total CP intake, duodenal OM and CP flows, and total tract OM and NDF digestibilities increased (linear; P