Secretion and reabsorption of endogenous protein along the small intestine of sheep: estimates derived from 15N dilution of plasma non-protein-N.
Sheep fitted with a PVC cannula in the dorsal rumen, a silastic infusion tube in the abomasum, and single "T'-shape PVC cannulas in the proximal duodenum (D1), distal duodenum (D2), mid-jejunum (J), and terminal ileum (I), were fed on diets varying in crude protein (N x 6.25) and fibre contents. 15N was administered to the sheep as a 15N-labelled grass meal-beer yeast suspension which was continuously infused into the abomasum over a period of 1 week. Subsequently, over a period of 4 d, 15N excess in the D1, D2, J and I digesta and faeces was measured and related to 15N excess in blood plasma TCA-soluble N. Average daily intakes of DM and N were 1.12 kg and 26.3 g respectively. Average daily endogenous N (g) amounted to 3.1 at D1, 10.2 at D2, 6.1 at J, 5.0 at I, and 5.1 in the faeces (F). Corresponding percentage values for total N were: D1 12.4, D2 32.9, J 46.4, I 48.4 and F 50.7. The secretion, particularly of pancreatic juice and/or bile, varied. The apparent re-absorption of endogenous protein varied among experimental diets, on average by 50.4% between D2 and I. Along the small intestine the percentage of 15N in the TCA-precipitable fraction gradually changed, on average by 66.0, 63.0, 46.3 and 55.7 at D1, D2, J and I respectively. Because of differential rates of enrichment and turnover among protein pools which contribute towards endogenous secretion, care should be taken in interpreting these data as absolute values.
Van Bruchem
J
J
Wageningen Institute of Animal Sciences (WIAS), Agricultural University, The Netherlands.
Voigt
J
J
Lammers-Wienhoven
T S
TS
Schönhusen
U
U
Ketelaars
J J
JJ
Tamminga
S
S
D000821:Animal Feed; D000818:Animals; D005243:Feces / Q000737:chemistry; D007408:Intestinal Absorption / Q000502:physiology; D007421:Intestine, Small / Q000378:metabolism*; D008297:Male; D009584:Nitrogen / Q000032:analysis / Q000097:blood; D009587:Nitrogen Isotopes; D011506:Proteins / Q000378:metabolism*; D011865:Radioisotope Dilution Technique; D012756:Sheep / Q000378:metabolism / Q000502:physiology*
D009587:Nitrogen Isotopes; D011506:Proteins; D009584:Nitrogen