THE POST-RUMINAL DIGESTION OF DRY-MATTER, NITROGEN AND AMINO-ACIDS IN WHEAT-BASED DISTILLERS DRIED GRAINS AND CANOLA-MEAL

The degradation of dry matter (DM), nitrogen (N) and amino acids (AA) by ruminal microorganisms (ruminal disappearance) in distillers' dried grains with solubles (DDG), groups DG1, DG2 and DG3, prepared from 70%, 75% and 100% wheat grain, respectively, and the remainder maize grain, plus a sample of canola meal (CM) was determined by incubating sample-filled Dacron bags for 12 h in sacco. The total digestion of nutrients was determined using a sequence of in sacco ruminal incubation for 12 h, in vitro digestion in acid-pepsin and with Dacron bags as mobile bags post-abomasally. A collection of mobile bags, via a cannula at the terminal ileum provided an estimate of ileal disappearance, which was a sum of digestion in the rumen, abomasum and small intestine. Recovery of mobile bags in feces provided an estimate of total tract digestion, defined as fecal disappearance, which was ileal disappearance plus the effects of the passage of sample-filled Dacron bags through the large intestine. Acid detergent insoluble N (ADIN) was 16.7%, 8.9% and 9.7% of total N in DG1, DG2 and DG3, respectively. ADIN was 5.7% of total N in CM. Both ADIN, with DG1 lower than DG2, and the composition of fermentative substrate, with DG3 lower than DG2, influenced the ruminal disappearance of DM, N and amino acids in DDG. The ruminal disappearance of DM, N and AA was higher for CM than all three groups of DDG. The ileal disappearance of N and AA was lower with DG1 than DG3 and was the result of a combined effect of ADIN and the composition of fermentative substrate, while there were no consistent differences between CM and DDG. Ileal estimates of disappearance were more sensitive than fecal-based data in identifying differences for total tract digestion among groups of DDG. Except for lysine, whose concentration in DDG was 40% that in CM, the estimated mean weight of AA digested post-ruminally (ileal disappearance minus ruminal disappearance) ranged from + 9% + 133% higher for DDG than CM.