Ph D Thesis Amelie Deglaire - TEL

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intake stimulated the synthesis, secretion and activity of proteolytic enzymes (Hee et al.,
1988a).
Postprandial exocrine pancreatic secretion was reported to be higher than preprandial
secretion in its volume and its protein content, but this was not affected by the amount of
food intake per se (Botermans & Pierzynowski, 1999). The food intake pattern has been
reported to affect exocrine pancreatic secretion: feeding 12 small meals to growing pigs
(16−31 kg), compared with one large meal daily, tended to stimulate protein output from
exocrine pancreatic secretions by 44% (Botermans et al., 2000).
In summary, Juste (1982) reported values for pancreatic secretions ranging from 1.5 to 4
g N/d in 35−40-kg pigs fed a standard diet containing 15% protein, values that are similar
to those reported in Table 6.
1.5. Small intestine
The small intestine is functionally divided into duodenum, jejunum (two-fifths of the
length of the small intestine) and finally ileum, structurally indistinct from the jejunum
(Sanford, 1982). The small intestine can synthesize up to 400 g protein/d in pigs
(Souffrant et al., 1993), which is one of the highest synthesis rate capacities in the body.
The N input from the small intestine has been reported to be higher than that produced
from bile, pancreas and stomach together (Juste, 1982). Quantitative and qualitative
estimations of intestinal secretions are difficult because of the constant entry of N, at
multiple stages, and because of constant reabsorption. Total N secreted in intestinal juice
has been reported to amount to 8.9 g N/d, when determined by digesta exchange between
15
N-labelled 30-kg pigs (Krawielitzki et al., 1990), and up to 15 g N/d, when determined
in intestinal loops of 35−50-kg pigs perfused with isotonic osmotic solution
(Buraczewska, 1979).
Dietary factors have been reported to influence intestinal secretions. Intestinal secretions
of N compounds were markedly decreased in pigs fed a protein-free diet (Buraczewska,
1979). A stimulating effect of dietary fibre has been reported; infusion of guar gum
solution (6.7 g/L) in isolated jejunal loops increased N secretion from the mucosa of the
entire small intestine from 15 to 27 g/d (Low & Rainbird, 1984). Their net influence on
endogenous N recovered at the terminal ileum is detailed in Section IV.
Intestinal endogenous N arises from mucins, epithelial enzymes (aminopeptidases,
maltases, lactases etc.), pancreatic enzymes, desquamated cells and, to a lesser extent,