Effects of forage percentage and canola seed on ruminal protein metabolism and duodenal flows of amino acids in steers.

The objective was to determine the effects of dietary forage percentage and fat supplementation on ruminal N metabolism, duodenal flows of AA, and digestion of N. Six ruminally and duodenally cannulated steers were offered six isonitrogenous diets for ad libitum intake twice daily in a 6 x 6 Latin square design. Treatments were arranged as a 2 x 3 factorial with two forage percentages (70 vs. 30% of dietary DM as corn silage) and three forms of canola seed supplementation, including no canola seed or canola seed added at 10% of dietary DM as whole seed treated with alkaline H2O2 or as crushed seed. No interactions between dietary forage percentage and canola seed supplementation occurred for any of the measurements. Duodenal flows of NAN and AA were greater for diets containing low forage than for diets containing high forage. However, duodenal flows of total N and NAN did not differ among diets when corrected for differences in intake. Efficiency of bacterial protein synthesis and duodenal flows of bacterial N and AA were increased when treated whole canola seed was supplemented. Apparent total tract digestibility of N was not altered by dietary forage percentage or canola seed supplementation. Results indicate that fat supplementation from canola seed (at 5% of dietary DM), in either form, had no effects on ruminal N metabolism or flows of AA to the duodenum and suggest that treated whole canola seed may stimulate ruminal bacterial protein synthesis.