Characteristics of ruminal and total tract digestion of canola meal and soybean meal in a high-energy diet for feedlot cattle

Four Holstein steers (233 kg) with ruminal cannulas and "T" cannulas in the proximal duodenum were used in a 4 X 4 Latin square experiment to evaluate characteristics of ruminal and total tract digestion of a generic (CM-40, 40% CP) and a high-protein (CM-46, 46% CP) variety of canola meal (CM) compared with a conventional, solvent-extracted soybean meal (SBM). Treatments consisted of an 80% concentrate diet that contained 20% tapioca (TP) or 20% of the respective test protein sources. Supplemental proteins replaced TP in the basal diet. Intake of dietary treatments was restricted to 5.0 kg/d (DM basis, 2.2% BW). Ruminal digestion of OM was similar (P > .10) for the CM-supplemented diets. Ruminal digestion of OM was higher (5.8%, P < .01) for SBM than for CM diets. Ruminal digestibility of ADF was similar (P > .10) across treatments. Ruminal degradation of feed N was similar (P > .10) for CM diets but tended to be greater (6.7 %, P < .10) for SBM. Ruminal degradation of N in CM-40, CM-46, and SBM averaged 71, 73, and 80, respectively. Passage of individual amino acids to the small intestine was similar for CM and SBM diets. Total tract DM digestibility (DMD) was similar (P > .10) for the CM diets. Total tract DMD was higher (2.9%, P < .01) for SBM than for CM diets. Total tract digestibility of ADF also tended to be higher (14; P < .10) for SBM than for CM diets. The DE (megacalories/kilogram) of the CM and SBM diets were greater (P < .01) than for the TP diet. The DE was greater (2.6%; P < .05) for the SBM diet than for the CM diets. The DMD of CM-40, CM-46, and SBM were 82, 82, and 92%, respectively. The corresponding OM digestibilities were 87, 86, and 98%, respectively. The DE values for CM-40, CM-46, and SBM were 4.12, 4.12, and 4.57 Mcal/kg, respectively. Canola meal is a relatively high-energy feedstuff that is slightly superior to SBM as a source of ruminal escape protein.