Effect of enzyme supplementation of a rye-based diet on xylanase activity in the small intestine of broilers, on intestinal crypt cell proliferation and on nutrient digestibility and growth performance of the birds.

1. A study was undertaken to investigate the susceptibility to peptic digestion of exogenous xylanase (EC 3.2.1.8) from Trichoderma longibrachiatum, added to a rye-based diet for broiler chickens, in order to elucidate its possible site of action. 2. It was also designed to investigate the effects of the enzyme (plus exogenous protease EC 3.4-24.28) when added to a rye-containing diet (60% rye/kg diet) on crypt cell proliferation in the mucosa of the small intestine, on short chain fatty acid (SCFA) concentrations in the small intestine digesta and in portal blood and on nutrient digestibilities. 3. In Experiment 1, the enzymes were added at activities 10x and 30x those recommended in commercial practice, but in Experiment 2 the activities were the recommended levels. 4. A significant proportion (estimated to be 15 to 20%) of the xylanase added at the higher concentration (15,000 and 45,000 units/kg diet) remained active in the small intestine of the growing chicken. 5. The crypt cell proliferation rate in birds fed on the control diet (45 cells/2 h) was significantly higher than in birds fed on the diets supplemented with enzyme at the higher level (29 and 33 cells/ 2 h), but there was no significant effect on SCFA. In birds fed on the diet supplemented with enzyme at the commercial level there was no clear-cut effect on crypt cell proliferation but exogenous xylanase could be detected in the small intestine. Intestinal fluid viscosity was reduced and growth performance of the birds was improved by the supplementation with exogenous enzymes. 6. Part of the improvement in growth performance could be ascribed to a 25% increase in the digestibility of nitrogen and a doubling of the digestibility of fat.