Response of broiler chickens fed wheat-based diets to xylanase supplementation
The objective of this study was to evaluate the effect of xylanase supplementation on performance, footpad score (FPS), nutrient digestibility, and intestinal morphometry in broiler chickens. Two-hundred-eighty-eight Ross 308 broiler chicks (one d old) were placed in one of 3 experimental treatments: positive control (PC), negative control (NC) (−150 kcal/kg), and XYL (NC supplemented with xylanase). Each treatment had 8 replicates with 12 animals each. Starter (zero to 21 d) and grower (21 to 42 d) diets, based on wheat and soy-bean meal, were available ad libitum. Body weight gain (BWG) and feed intake were measured, and mortality corrected feed conversion ratio (FCR) was calculated. The relative weights of the empty gastrointestinal tract compartments and FPS were recorded on d 21 and d 42. On d 42, ileal contents were collected for nutrient digestibility determination. Statistical comparisons were performed using one-way ANOVA (JMP Pro 12). The reduction of energy resulted in lighter birds at the end of the study (PC: 2,710 vs. NC: 2,546 g; P = 0.030) whereas xylanase supplementation numerically increased BWG by 84 g (P = 0.229) and improved FCR by 12 points (P = 0.145) compared with the NC. Significant differences in FPS were observed on d 21. Score 0 (no lessions) was predominant in PC and XYL treatments, while score 1 (mild lesions) had a higher frequency in NC birds. Xylanase supplementation numerically increased organic matter (5.9%) and energy (4.7%) utilization with values above those observed with the NC. No treatment effects were observed in any of the morphometric measurements, with the exception of the gizzard (P = 0.036) and the ileum (P = 0.088) on d 42. Xylanase resulted in higher relative gizzard weights compared to NC (P = 0.102). Supplementation of broiler diets with xylanase tended to influence performance, which may be due to a better utilization of nutrients. The increase in gizzard and ileum weights in birds 42 d but not 21 d of age suggests an adaptive response that takes time to develop.