Exogenous xylanase improves broiler production efficiency by increasing proximal small intestine digestion of crude protein and starch in wheat-based diets of various viscosities

Changes in small intestine digestion kinetics and early enzymatic hydrolysis in the crop attributable to xylanase supplementation has not previously been thoroughly studied in relation to animal performance. The current paper reports the effects on broiler performance of a commercial mono-component GH11 xylanase added to normal and high viscous wheat-based broiler diets with emphasis on the site of early enzymatic hydrolysis as indicated by nutrient digestibility kinetics, and visual cereal cell wall degradation. The study was conducted using 2850 1-day old male Ross 308 broilers, allocated to 5 dietary treatments: (1) positive control, an optimized diet based on wheat, soy and corn; (2) negative control; (3) negative control of high viscosity; (4) negative control supplemented with xylanase; (5) negative control of high viscosity supplemented with xylanase. Both negative control and negative control high viscosity diets were reduced in apparent metabolizable energy (starter 3.3 %, grower 7.0 % and finisher 8.5 %) as well as digestible amino acids compared to the positive control, achieved by substituting corn for rye and wheat-coproducts. The xylanase was supple-mented at 150 FXU/kg to treatment 4 and 5. Each treatment was fed ad lib to 19 replicated pens of 30 birds. The BW, feed intake (FI) and FCR were measured from d0-35 and intestinal viscosity and nutrient digestibility on d28. Statistical comparisons were performed using a mixed model. All negative controls had higher FI than the positive control regardless of xylanase supplemen-tation. The negative control with high viscosity supplemented with xylanase had an increased BW at d35 compared to all other treatments. The xylanase improved d35 FCR compared to the unsupplemented diets resulting in a European efficiency factor similar to the positive control. Microscopy of digesta samples helped visualize that the exogenous enzymatic degradation of the cereal cell wall components commenced already in the crop and increased throughout the in-testinal tract. This was accompanied by reduced jejunal and ileal digesta viscosity for the xylanase supplemented treatments. Depending on diet, the xylanase improved jejunal, but not ileal, digestibility of several nutrients including starch and protein. In conclusion, it is suggested that improved growth performance is caused by an array of multifactorial effects such as viscosity reduction, cell wall degradation and changes in the intestinal site of digestion. The current results display the potential of using xylanase in diets containing what is generally considered as lower quality arabinoxylan rich feedstuffs.

Automated summary

The study thoroughly investigated the effects of xylanase supplementation on broiler performance and compared different dietary treatments. Results showed that xylanase had positive effects on reducing intestinal viscosity, degrading cereal cell walls, and changing the site of digestion, leading to improved growth performance in broilers.