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

Abstract

Summary Five sheep, fitted with a PVC cannula in the dorsal rumen, a silastic infusion tube in the abomasum, and a single T‐shape PVC cannula in the proximal duodenum (D1), distal duodenum (D2), mid‐jejunum (J) and terminal ileum (I), were fed diets, which varied in crude protein (N × 6.25) and fibre contents. A 15N labelled grass meal‐beer yeast suspension was continuously infused into the abomasum over a period of 1 week. Subsequently, over a period of 4 days, the 15N excess in D1, D2, J and I digesta was related to 15N excess in blood plasma TCA soluble N. The average daily intakes of dry matter and N were 1.02 kg and 25.9 g, respectively. Average daily endogenous N amounted to 4.3 g at D1, 11.1 g at D2, 5.9 g at J and 4.8 g at I. Corresponding percentages of total N flow were: 15.0 (D1), 33.4 (D2), 44.6 (J) and 47.0 (I), respectively. The difference between distal and proximal duodenal endogenous N flow, the jejunal endogenous N flow and the ileal endogenous N flow were positively related to the amount of N, entering the small intestine (R2 = 0.69, 0.81 and 0.63, respectively). The ileal endogenous N flow was also positively related to the small intestinal NDF/DM/non‐protein DM flow and faecal dry matter flow (R2 = 0.81, 0.62, 0.59, 0.91, respectively). The apparent re‐absorption of endogenous protein varied among experimental diets, and was on average between D2 and I 56.0%. Zusammenfassung Die Wirkung von Faser, Trockensubstanz und Protein auf die Passage von endogenem Stickstoff im Dünndarm des Schafes In Experimenten (3 times 3 und 2 times 2) an insgesamt 5 Schafen, die mit einer PVC Kanüle im dorsalen Pansen, einem Labmagenkatheter und mit T‐formigen PVC Kanülen am proximalen Duodenum (D1), distalen Duodenum (D2), mittlerem Jejunum (J) und terminalen Ileum (I) sowie mit einem Katheter in der V. jugularis ausgerüstet waren, wurden Rationen eingesetzt, deren Faser‐ und Rohproteingehalt variierte. In der Tagesration waren 668–1193 g DM, 150–676 g NDF und 22–32 g N enthalten. Die Tiere wurden durch eine 7tägige intraabomasale Infusion einer Mischung von 15N‐Gras und 15N‐Hefe mit 15N markiert. 14 h nach Beendigung der Infusion wurde über eine Periode von 4 Tagen die 15N‐Anreicherung in der Digesta von D1, D2, J und I gemessen und mit der 15N‐Anreicherung in der TCA‐löslichen N‐Fraktion des Blutplasmas in Beziehung gesetzt. Die durchschnittliche tägliche Menge an endogenem N (Ne) belief sich von D1 bis I auf 4.3, 11.1, 5.9 und 4.8g. Das entsprach 15.0, 33.4, 44.6 und 47.0% der Passage an Gesamt‐N. Die Differenz im Fluß an Ne zwischen distalem und proximalem Duodenum sowie der Fluß von Ne am Jejunum und Ileum war positiv mit der N‐Passage an D1 korreliert (R2 = 0.69, 0.81 und 0.63). Der ileale Fluß von Ne war positiv korreliert mit der ilealen Passage von NDF, DM, und Nicht‐Protein‐DM sowie der DM‐Ausscheidung im Kot (R2 = 0.81, 0.62, 0.59 und 0.91). Die scheinbare Re‐Absorption von Ne varierte zwischen den Rationen. Im Durchschnitt wurden zwischen D2 und I 56% des Ne reabsorbiert. Es wird gefolgert, daß erhebl...

Studies on N-metabolism in different gastrointestinal sections of sheep using the digesta exchange technique. 2. Passage of endogenous nitrogen

“…Recently experiments of Voigt et al (1996) and Van Bruchem et al (1997) using intra-abosomal 15 N infusion to multifistulated sheep resulted in an average of 3.1 g endogenous N at the proximal duodenum, which is 12% of the total N flux at the duodenum and corresponds to 2.8 g/kg DM intake. Lammers-Wienhoven et al (1998) who used the same method estimated a higher value: 4.3 g endogenous N, equivalent to 15% of total N flux at the duodenum or 4.2 g/kg DM intake. Brandt et al (1980) estimated, by the use of intraruminal 15 N infusion, similar values in dairy cows (3.6 g endogenous protein N/kg DM passage at the proximal duodenum or 9-12% of NAN flow).…”

“…This higher CF content gives rise to enhanced sloughing of epithelial cells and therefore to a higher endogenous NAN flux into the duodenum. Recently, Lammers- Wienhoven et al (1998) demonstrated in sheep that the flow of endogenous N into the duodenum increased from 20 to 28%) of total N flow if the dietary NDF content was increased from 15 to 68%.…”

“…Assuming that the 15 N at % excess of endogenous N and of the TCA soluble N fraction of the plasma is identical (Lammers-Wienhoven et al, 1998), the amounts of endogenous N passing the duodenum and the ileum can be estimated as follows: The estimation of flow rates of endogenous N into the duodenum was not possible for labelled animal No. 1, since the 15 N present in its duodenal digesta consisted of infused urea 15 N and 15 N of endogenous origin.…”

Studies on N-metabolism in different gastrointestinal sections of sheep using the digesta exchange technique. 3. N secretion and reabsorption

“…These authors found average values of 50%). In the studies of Lammers-Wienhoven et al (1998) the N reabsorbility amounted to 56%. These differences are likely due to the mode of calculation.…”

“…Thus the net N secretion into the rumen and the abomasum could be calculated using the quotient of 15 N enrichment in the duodenal digesta and the TCE soluble blood plasma of the animal No. 2 (Lammers-Wienhoven et al, 1998). The N secreted by bile and the pancreatic fluid (Sandek et al, 2001a) was subtracted from this value.…”