Interrelationship of diet fibre and endoxylanase with bacteria in the chicken gut

Abstract

Four trials were conducted to assess the influence of non-starch polysaccharides (NSP) from dietary corn (C), wheat (W) and wheat supplemented with endoxylanase (E) on performance, the gastrointestinal tract and on the bacterial population and its fermentation characteristics in broiler chickens. Trial one determined the difference in GIT size, specific culturable intestinal bacteria numbers, and volatile fatty acid (VFA) production at 42 d between C, W and wheat diets supplemented with E either throughout the 42 d or for 0-28 d or 29-42 d. The second trial utilized the same wheat treatments as the first trial, but GIT and VFA measures were taken at 14, 28 and 42 d while bacterial enumeration was only done at 28 and 42 d. This experiment was analyzed as a two-way analysis of variance with age and treatment effects. A third trial evaluated the C, W and E diets for differences in the amounts of total aerobic and anaerobic bacteria cultured at 28 and 42 d. The fourth trial was a two-way analysis of variance evaluating the effect of age and diet (C, W and E) on performance, GIT size, VFA production and residual NSP in the terminal ileum at 7, 14, 21, 28, 35 and 42 d. Performance was measured in all four trials and digesta viscosity was measured in all but the third trial. Results from the first trial showed that E supplementation of wheat diets improved performance. Viscosity was lowest for C diets. Measures of GIT size were all smaller on C versus wheat-based diets. Ileal anaerobes tended to be higher with E than without while caecal anaerobes were higher on unsupplemented wheat diets. VFA production was higher for wheat versus corn fed birds in the ileum. C diets and wheat diets where E was removed at 28 d yielded the highest caecal propionic acid levels. In the second trial, performance was also improved with E supplementation. Viscosity was lower for E supplemented wheat-fed birds than unsupplemented birds, except at 42 d. Full ileal weights were higher for W diets versus all others while caecal weights were lower on this diet. Bacterial data indicated higher levels of ileal anaerobes and some caecal anaerobes on W diets at 28 and 42 d. VFA content of the digesta, at 28 d was higher in the ileum in diets without E and the same tendency was noted for caecal VFA. At 42 d ileal VFA production was higher with E and caecal VFA production was higher without E. The results from the first two trials demonstrate that while certain anaerobic bacteria do increase in the ileum of W diets, others appear to respond to the substrates created by E supplementation in both the ileum and the caecum. Age related adaptation also appears to affect the response of the bacteria to E supplementation. In the third experiment C and E birds performed equally well with W birds having the highest gain to feed ratios after 14 d and overall. E diets resulted in the highest numbers of caecal anaerobes with C birds having the lowest number. At 42 d, birds had higher numbers of caecal anaerobes than at 28 d. At 28 d, caecal aerobes were highest on E diets (P