Mechanisms Of Xylanase On Broilers Fed Wheat-based Diets

The objective was to study the application of a xylanase on broiler production and its mechanism. The study included two parts.The first part, comprising a growth trial and a metabolism trial, was conducted to investigate the effects of dietary enzyme supplementation on performance, nutrient digestibility, intestinal morphology, digestive organ size, and volatile fatty acid profiles in the hindgut of broiler chickens fed wheat-based diets. The experimental diets in both trials consisted of a wheat-based control diet supplemented with 0, 200,400, 600, 800, or 1000 mg/kg xylanase. Diets were given to the birds from d 7 to 42 of age. In the growth trial, enzyme supplementation improved broilers average daily gain and decreased F/G (feed over gain ratio) linearly (P<0.01) with increasing levels of enzyme supplementation. Enzyme inclusion decreased the size of the digestive organs and the GIT (gastrointestinal tract) to some extent. The relative length of each intestinal segment decreased linearly (P<0.05). The relative weight of the AI (anterior intestine) on d 21 and ileum on d 42 also decreased linearly (P<0.01). On d 21 and 42, there were negative linear (P<0.05) relationships between increasing enzyme supplementation and the relative weight of the liver and pancreas, respectively. Furthermore, there was a linear (P<0..01) increase in total volatile fatty acid content of cecum in two phases and of ileum only on d 21. During each period of the metabolism trial, ACPD (apparent crude protein digestiblity) decreased linearly (P<0.05), while no differences were detected (P>0.05) in AME (apparent metabolizable energy).The second part, another metablisable trial, was carried out to study the effects of enzyme inclusion on digesta transit time of broilers fed wheat-based diets. The experiment diets were designed to two varieties of wheat supplemented with and without 0.04% enzyme. Thirty six male birds at the age of 6 wk were randomly allotted to each treatment with nine replications. Chromium oxide was used as a marker. After force-intake of 45 g feed, feces were collected at the time of 1, 2, 3, 4, 5, 7, 9, 12, 15, 18, 21 or 24 h. Then concentration of Chromium oxide was calculated as non-cumulative or cumulative data. The experiment results demonstrated that enzyme could accelerate digesta transit time of birds fed wheat-based diet. Furthermore, the peak excretion appeared about 1 h earlier.