Effect of cell walls, dry matter and protein supply on endogenous nitrogenflow in the small intestine of sheep

Five sheep, fitted with a PVC cannula in the dorsal rumen, a silastic infus ion tube in the abomasum, and a single T-shape PVC cannula in the proximal duodenum (D-1), distal duodenum (D-2), mid-jejunum a, and terminal ileum (I ), were fed diets, which varied in crude protein(N x 6.25) and fibre conten ts. A N-15 labelled grass meal-beer yeast suspension was continuously infus ed into the abomasum over a period of 1 week. Subsequently, over a period o f 4 days, the N-15 excess in D-1, D-2, J and I digesta was related to N-15 excess in blood plasma TCA soluble N. The average daily intakes of dry matt er and N were 1.02 kg and 25.9 g, respectively. Average daily endogenous N amounted to 4.3 g at D-1, 11.1 g at D-2, 5.9 g at J and 4.8 g at I. Corresp onding percentages of total N flow were: 15.0 (D-1), 33.4 (D-2), 44.6 a, an d 47.0 (I), respectively. The difference between distal and proximal duoden al endogenous N flow, the jejunal endogenous N flow and the ileal endogenou s N flow were positively related to the amount of N, entering the small int estine (R-2 = 0.69, 0.81 and 0.63, respectively). The ileal endogenous N fl ow was also positively related to the small intestinal NDF/DM/non-protein D M flow and faecal dry matter flow (R-2 = 0.81, 0.62, 0.59, 0.91, respective ly). The apparent re-absorption of endogenous protein varied among experime ntal diets, and was on average between D-2 and I 56.0%.