THE POST-RUMINAL DIGESTION OF DRY-MATTER, NITROGEN AND AMINO-ACIDS INWHEAT-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 gra in, plus a sample of canola meal (CM) was determined by incubating sam ple-filled Dacron bags for 12 h in sacco. The total digestion of nutri ents was determined using a sequence of in sacco ruminal incubation fo r 12 h, in vitro digestion in acid-pepsin and with Dacron bags as mobi le 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. Re covery of mobile bags in feces provided an estimate of total tract dig estion, defined as fecal disappearance, which was ileal disappearance plus the effects of the passage of sample-filled Dacron bags through t he 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% o f total N in CM. Both ADIN, with DG1 lower than DG2, and the compositi on of fermentative substrate, with DG3 lower than DG2, influenced the ruminal disappearance of DM, N and amino acids in DDG. The ruminal dis appearance 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 a nd was the result of a combined effect of ADIN and the composition of fermentative substrate, while there were no consistent differences bet ween CM and DDG. Ileal estimates of disappearance were more sensitive than fecal-based data in identifying differences for total tract diges tion among groups of DDG. Except for lysine, whose concentration in DD G was 40% that in CM, the estimated mean weight of AA digested post-ru minally (ileal disappearance minus ruminal disappearance) ranged from + 9% + 133% higher for DDG than CM.