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Effects of dietary supplementation with xylanase on growth performance, ileal digesta viscosity, apparent ileal digestibility and excreta noxious gas emission of broilers fed wheat-based diets
This study was conducted to evaluate the effects of dietary xylanase supplementation in wheat-based diets on growth performance, ileal digesta viscosity, apparent ileal digestibility and excreta noxious gas emission of broilers. A total of 600 one-d-old male Ross 308 broilers were used in this 35 d growth trial. Birds with an initial average BW of 43 ± 0.6 g were randomly allotted into 4 treatments with 10 replicate pens per treatment and 15 broilers in each pen. Dietary treatments were as follows: (1) CON, basal diet; (2) T1, basal diet + 0.0125% xylanase (the concentration guaranteed 9000U/g); (3) T2, basal diet + 0.025% xylanase; (4) T3, basal diet + 0.0375% xylanase. Broilers were weighed and feed consumption was recorded by pen on d 0, 18 and 35, to calculated BWG, ADFI and FCR. From d 29 to 35, Cr2O3 was used as an indigestible marker and supplemented to the diets at a level of 2 g/kg. On d 35, 120 chicks (3 per pen and 30 per treatment) were slaughtered and the ileal digesta was immediately collected for determining the ileal digesta viscosity and apparent ileal digestibility (AID) of nutrient. For analysis of excreta noxious gas emission, fresh excreta samples from each pen were collected in 2.6-L plastic boxes at the end of experiment. All data were analyzed by using GLM procedure of SAS, orthogonal polynomial contrasts were used to test the linear and quadratic effects of the increasing levels of xylanase. Statements of statistical significance were based on P<0.05. Dietary addition of xylanase improved (linear, P<0.05) the BWG and decreased (linear, P<0.05) the FCR during 1-18 d and 0-35 d. Oral administration of xylanase led to a decrease (linear, P<0.01) in ileal digesta viscosity. In addition, the AID of DM, CP, energy and most amino acids, with the exception of Ile, Phe, Asp, Glu and Pro, were improved (linear, P<0.05) by xylanase supplementation. Furthermore, xylanase supplementation reduced excreta NH3 (linear, P<0.05; quadratic, P<0.05) and R.SH (linear, P<0.01) emission. In conclusion, dietary xylanase supplementation in broilers wheat-based diets could mitigate the detrimental effect of NSP from wheat, reduce the viscosity of gut contents and improve nutrient digestibility, thus improving broilers growth performance. Moreover, inclusion of xylanase not only led to more consistent and uniform performance, but it also reduced the release of odor emissions from broiler houses.