Intestinal development and body growth of broiler chicks on diets supplemented with non-starch polysaccharides

The growth of broiler chicks and the mechanisms underlying responses to die ts supplemented with commercial non-starch polysaccharides were evaluated. The supplements varied in viscosity and chemical structure and evaluation w as conducted over mio feeding periods. The viscosity of the four supplements tested ranged from 1.38 cP for algini c acid (AL) to over 2000 cP for guar gum (GG) and gum xanthan (GX). The who le diet followed a similar trend. The ileal digesta viscosity was significa ntly highest (P < 0.001) in chicks that were fed the GX diet. Over a period of 7 days of feeding the diets, there was a significant reduc tion (P < 0.001) in the final body weight and weight gain of chickens on di ets supplemented with GG and GX. Supplementation with GG and GX also result ed in a deterioration (P < 0.001) in FCR. The weight of the small intestine was higher (P < 0.001) on the GG-suppleme nted diet than on the other dirts while small intestinal fill was increased by the presence of GG and GX. There was no significant variation in the mu cosal morphometry of birds on the different diets. Jejunal maltase and sucr ase activities were highest (P < 0.001) in chicks that were fed the AL-supp lemented diet and lowest in chicks fed the GX-supplemented diet. The activi ty of aminopeptidase N in the ileum was stimulated (P < 0.05) by GIG. The u ptake of L-tryptophan into brush-border membrane vesicles was unaffected by NSP supplement. After a second period of feeding the diets containing NSP at half the level present in the first period, final body weight and weight gain were signif icantly higher (P < 0.001) on the gum arabic (GA)-supplemented diet than on the other diets. Absolute feed intake (P < 0.05), feed intake per unit of initial body weight (P < 0.001) and FCR (P < 0.001) were significantly affe cted by the supplements, being higher in chicks on the OX-supplemented diet than on the other diets. The weight (P < 0.001) and capacity (P < 0.01) of the small intestine were highest in chicks on the GG- and OX-supplemented diets, respectively. The c rypt depth of the jejunal mucosa was higher(P < 0.01) in chickens on the GX -supplemented than in the other chickens. Ileal crypts were deepest and vil li longest (P < 0.05) in chicks on the GG- and GA-supplemented diets, respe ctively. Jejunal mucosal DNA (P < 0.05) and RNA (P < 0.001) contents of chicks were significantly increased by the GA-supplemented diet. In the ileum, RNA cont ent (P < 0.01) and RNA:DNA ratio (P < 0.001) were reduced in chicks raised on the more viscous diets. Ileal maltase activity was also significantly higher (P < 0.01) in chicks o n the GX diet than in chicks on the other diets, L.-Tryptophan uptake by il eal brush-border membranes was lowest (P < 0.05) in chicks on the GA-supple mented diet. (C) 2001 Elsevier Science B.V. All rights reserved.