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

Abstract

The growth of broiler chicks and the mechanisms underlying responses to diets supplemented with commercial non-starch polysaccharides were evaluated. The supplements varied in viscosity and chemical structure and evaluation was conducted over two feeding periods. The viscosity of the four supplements tested ranged from 1.38 cP for alginic acid (AL) to over 2000 cP for guar gum (GG) and gum xanthan (GX). The whole diet followed a similar trend. The ileal digesta viscosity was significantly 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 reduction (P< 0.001) in the final body weight and weight gain of chickens on diets supplemented with GG and GX. Supplementation with GG and GX also resulted in a deterioration (P < 0.001) in FCR. The weight of the small intestine was higher (P < 0.001) on the GG-supplemented diet than on the other diets while small intestinal fill was increased by the presence of GG and GX. There was no significant variation in the mucosal morphometry of birds on the different diets. Jejunal maltase and sucrase activities were highest (P < 0.001) in chicks that were fed the AL-supplemented diet and lowest in chicks fed the GX-supplemented diet. The activity of aminopeptidase N in the ileum was stimulated (P <0.05) by GX. The uptake 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 significantly 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 affected by the supplements, being higher in chicks on the GX-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 GX-supplemented diets, respectively. The crypt 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 villi longest (P < 0.05) in chicks on the GG- and GA-supplemented diets, respectively. 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 content (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 on the GX diet than in chicks on the other diets. L-Tryptophan uptake by ileal brush-border membranes was lowest (P < 0.05) in chicks on the GA-supplemented diet.