SUMMARY

Ninety-six Simmental x Angus crossbred weanling heifer calves (239 ± 2.3 kg) were used in four replications to evaluate three dietary treatments in Trial 1. Treatments were cracked corn-hay based diets supplemented with one of three corn wet milling industry co-products: dry corn gluten feed (DCGF), dried distillers grains (DDG), and a new modified corn fiber (MCF). In Trial 2, four ruminally cannulated mature crossbred beef steers (606 ± 60 kg) were utilized in a 4 × 4 Latin square with 11 d periods to determine digestibility and ruminal metabolism of limit-fed cracked corn-hay diets supplemented with: cornstarch (CON), DCGF, DDG, or MCF. An in situ study was conducted to compare the rate and extent of crude protein (CP) degradation of DCGF, DDG, and MCF.

There were no differences in initial weights or dry matter intake (DMI) of heifers fed the three treatments in Trial 1. Average daily gain and feed efficiency (G/F) were improved for heifers fed DCGF (P < .01) or DDG (P < .001) vs. heifers fed MCF. No differences in digestibilities of any nutrients or in ruminal VFA concentrations were observed in Trial 2 for steers fed DCGF or DDG vs. those fed MCF. Supplementing cornstarch (CON) resulted in decreased (P < .05) total dietary fiber (TDF) digestibility, tended (P <.10) to improve digestibilities of DM and OM, increased (P < .05) total VFA concentrations and concentrations of propionate and valerate, but decreased (P < .05) concentrations of butyrate, isobutyrate, and isovalerate when compared to DCGF, DDG, and MCF. Dry corn gluten feed had increased (P < .05) and DDG tended to have increased (P < .10) percentages of the immediately soluble fraction of CP 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 may be utilized in limit-fed high-energy diets without decreasing performance or digestibility. Feeding of MCF resulted in poorer performance of heifers; MCF may have limited feeding value because of poor digestion characteristics.