Digestion des protéines dans l'intestin grêle chez le porc. III. - Digestibilité des acides aminés et variations postprandiales de la composition des digesta selon la source de protéines d'un régime à base d'amidon de blé purifié

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Abstract
Four Large White castrated male pigs averaging 57 kg liveweight were fitted with a post-valvular ileo-colic fistula. They were fed daily either a protein-free diet or a diet including 16% crude protein supplied as fish-meal or wheat gluten. Total N and amino acid (A.A.) contents of the feeds were determined as well as those of the digesta collected from the terminal ileum 4, 6, 8, 14 and 24 h after the meal. Variations in the A.A. composition of digesta as well as apparent and true ileal digestibilities of each A.A. for wheat starch based diets were compared to previous results obtained with maize starch based diets. The total amounts of A.A. collected over 24 h in the distal small intestine were 19, 7 and 5 g, respectively, for the fish-meal, gluten and protein-free diets. The apparent ileal digestibility of individual A.A. was much higher with the gluten diet than with the fish-meal diet (except fort LYS, ALA and ARG). The corresponding true digestibilities were globally 3-4 points higher than the apparent digestibilities. This increase did not lead to a noticeable change in the A.A. hierarchy for fish-meal, while it led to a levelling of the values around 100% for gluten (except for LYS and ASX). The postprandial variation in the amounts of A.A. collected was very different with the fish-meal diet from that observed with the other diets. The mean A.A. composition of digesta considerably differed according to the dietary protein source. The A.A. composition of digesta after feeding the protein diet also varied during the 24 h period. The factorial analysis of variance (2 starches .times. 2 proteins) concerning the digestibilities of each A.A. showed that the influence of the protein source on the apparent or true digestibility was very important. The nature of the starch significantly affected the apparent digestibility of most A.A., but only the true digestibility of some of them. For both criteria the effect of the starch-protein interaction was significant in most of the cases. The protein source directly affected the ileal digestibility of A.A. The nature of the dietary starch seemed also to have an effect probably by modifying the proportion of endogenous proteins in the digesta, as shown by the comparison of the profiles of apparent and true digestibilities of A.A. for these wheat starch and maize starch based diets.