Abstract
This study evaluated carinata (CRM) versus canola meal (CM) fed alone or in combination with wheat-dried distillers’ grains with solubles (WDDGS)as a protein supplement for beef cattle. The trial was designed as a Latin square with 4 rumen-cannulated heifers (386 ± 27.95 kg; mean ± SD) fed a barley-based backgrounding (BK) diet with CRM (9.2% DM); CM (10.0% DM); CRM (5.0% DM) + WDDGS (5.3 DM); or CM (5.0% DM) + WDDGS (5.3 DM) as protein sources. Rumen and omasal samples were collected every 8 h for 3 d. Fecal output was collected every 2 h for 5 days. Omasal digesta flow and nutrient digestibility were measured with the triple marker technique using chromium-EDTA, ytterbium chloride and indigestible NDF. Microbial protein synthesis was determined using nitrogen labelled ammonium sulphate. Ruminal pH, ammonia, acetate, propionate and butyrate concentrations were not affected (P > 0.05) by treatment. No treatment differences were detected for omasal nutrient flow or apparent digestion of DM, OM or NDF, as well as for true ruminal OM digestion. Apparent digestion of N tended (P = 0.09) to be greater for CRM and CM diets relative to WDDGS diets (-10.0 ± 2.73 vs. 13.9 ± 14.81 g d(-1)). The inclusion of WDDGS increased (P = 0.04) N truly digested in the rumen (154.5 ± 0.16 vs. 177.9 ± 0.55 g d(-1)), and decreased (228.0 ± 2.45 vs. 205.6 ± 20.07 g d(-1)) ruminal non-ammonia nitrogen (NAN) flow. No treatment differences (P > 0.05) were noted in total bacterial NAN flow or in microbial efficiency. Total tract nutrient digestibility was not (P > 0.05) affected by treatment. These results indicate that CRM, relative to CM, does not affect rumen fermentation, nutrient utilization and microbial protein synthesis with no benefit to adding WDDGS as a rumen undegradable protein source.