Pigs were fed protein-free diets containing different pea inner fiber (PIF) isolates (from wrinkled or smooth peas, unprocessed or micronized) or different PIF levels (from 50 to 200 g/kg diet), and the flows of endogenous N and amino acids were measured at the ileum level. The flows were better correlated to the water-holding capacity (WHC) of the diet than to fiber intake (R 2 = 0.996 vs 0.76, respectively). The relationship with WHC was of the exponential type, with a high increase when the WHC exceeded 3 g of water/g diet. A similar pattern and correlation (R 2 = 0.98) was obtained for the ileal flow of nucleobases (markers of epithelial cells and bacteria), whereas the relationships with crude mucus (R 2 = 0.96) and diaminopimelic acid (marker of bacteria, R 2 = 0.55) were linear. N retention by pigs fed with 0, 30, 60, or 90 g/kg of dry matter (DM) of the same protein isolates did not differ significantly in pigs receiving a 40 or 160 g of PIF/kg diet, despite significant differences in ileal N and amino acid flows between the two fiber levels (2.0 and 3.1 g of N/kg of DM intake, on average). These results and those of the flow of endogenous N compounds suggest an effect of the swollen fibers on the intestinal wall rather than a disturbance of the digestive processes. Keywords: Pig; ileum; endogenous N; fiber; water-holding capacity

5 8oo Gembloux (Belgique) (**) Chaire de Physiologie animale et de Zootechrzie, Facaslté des Sciences agronomiques de l'État, 2 , passage des Dé!ZOVtés, B 5 8 0 o Gembloux (Hel giqi

caractéristique est exigée tant pour les études de digestibilité que pour celles visant à déterminer l'ingestion au pâturage. En outre, ils doivent rester associés aux constituants de la phase marquée, au cours du transit. Cette exigence est particulièrement importante pour les études de digestion menées sur des animaux munis de fistules simples. L'oxyde de chrome proposé par E DIN (101 8) comme indicateur inerte a été fort utilisé, principalement en vue de la détermination de digestibilité des rations par de nombreux auteurs, pour de nombreuses espèces animales (S CHUR C H , I,r,oYD