The effects of corn milling coproducts on growth performance and diet digestibility by beef cattle

Simmental x Angus weanling heifers (n = 96; 239 +/- 2.3 kg) were used in fo ur replications to evaluate three dietary treatments in Trial 1. Treatments were cracked corn-hay diets supplemented with one of three corn milling in dustry coproducts: dry corn gluten feed (DCGF), dried distillers grains (DD G), and a new modified corn fiber (MCF). In Trial 2, ruminally cannulated m ature crossbred beef steers (n = 4; 606 +/- 60 kg) were used in a 4 x 4 Lat in square with 11-d periods to determine digestibility and ruminal metaboli sm of limit-fed cracked corn-alfalfa haylage diets supplemented with cornst arch (CON), DCGF, DDG, or MCF. During Periods 3 and 4, an in situ study was conducted to compare the rate and extent of CP degradation of DCGF, DDG, a nd MCF. In Trial 1, there were no differences (P > .10) in initial weights or DM intake. Average daily gain and feed efficiency (G/F) were improved (P < .01) for heifers fed DCGF or DDG vs heifers fed MCF. In Trial 2, no diff erences (P > .10) in digestibilities of any nutrients or in ruminal VFA con centrations were observed for steers fed coproducts. The CON supplementatio n decreased (P < .05) total dietary fiber (TDF) digestibility, improved (P < .10) digestibilities of DM and OM, increased (P < .05) total VFA concentr ations and concentrations of propionate and valerate, and decreased (P < .0 5) concentrations of butyrate, isobutyrate, and isovalerate when compared w ith the coproducts. Dry corn gluten feed increased (P < .05) and DDG tended (P < .10) to increase percentages of the immediately soluble fraction of C P, and both had increased (P <.05) rates (K-d) and greater (P < .05) extent of ruminal CP degradation than MCF. These data suggest that DCGF and DDG m ay be utilized in limit-fed high-energy diets without sacrificing performan ce. Feeding of MCF resulted in poorer performance of heifers, suggesting a limited feeding value that results from high ADIN content and slow in situ protein digestion.