Determination of Nutrient Digestibility in Calves Supplemented with Various Levels of Corn Gluten Feed When Consuming Forage-based Rations

The experimental objective was to determine the effect of supplementing various levels of corn or corn gluten feed (CGF) on apparent total tract nutrient digestibility in cattle consuming a forage-based ration. Twelve purebred Angus and Simmental heifers were stratified across treatments by BW and breed in a 2x2 factorial arrangement across 2 periods (n = 6/treatment). Treatments included either corn or CGF supplemented at 0.25% BW or 0.75% BW with ad libitum access to alfalfa hay. Each period lasted 21 d, with animals housed as a group and moved to individual stalls to consume supplement each morning during the first 10 d and individually thereafter. Fresh alfalfa and supplement were provided daily throughout the experiment, and feed offered and refused were recorded daily while animals were housed individually. During the final 3 d of each period, fecal samples were obtained directly from the rectum of each animal every 6-h. Samples were analyzed for neutral detergent fiber (NDF), organic matter (OM), and crude protein (CP). Data were analyzed using lm in R with significance defined at P ≤ 0.05. The statistical model included the fixed effects of supplement type, level, and their interaction, breed, and period. No differences (P ≥ 0.28) in ADG or G:F were noted among treatments. Total tract NDF, ADF, and OM digestibility did not differ among treatments, but OM and ADF digestibility tended to be greater (P = 0.10 and P = 0.06, respectively) for animals supplemented with corn. Crude protein digestibility was not influenced by supplement type (P = 0.46), but tended to be greater (P = 0.07) for animals supplemented at 0.25% BW. These results indicate that at supplement levels below 0.75% BW, supplementing cattle with CGF does not result in an improvement in apparent total tract digestibility relative to corn under the conditions of this experiment.