Interaction between protease and xylanase in broiler chicken diets containing sorghum distillers' dried grains with solubles

Individual or combined effects of xylanase and protease on the nutritive value of diets containing sorghum distillers' dried grains with solubles (sDDGS) in broiler chickens were investigated. A total of 480 day-old male broiler chickens were assessed in a 3 × 2 × 2 factorial arrangement of treatments (0, 150 or 300 g sDDGS/kg diet, with or without xylanase, and with or without protease) in a 21 d study. Each of the 12 treatments was replicated 5 times, accommodating 8 birds per replicate. Feed intake and body weight gain (BWG) of the birds were increased (P < 0.001) by inclusion of sDDGS to the diets independent of enzyme supplementation. Feed conversion ratio (FCR) deteriorated (P < 0.001) with the incorporation of sDDGS into the diets at both levels. Protease improved feed consumption (P < 0.05) and BWG (P < 0.01) of the birds when assessed for the 21 d study with an interaction with inclusion of sDDGS (P < 0.05). Regardless of sDDGS and protease, xylanase significantly improved (P < 0.01) FCR at any period of the trial. Digestibility of protein and most amino acids was adversely affected (P < 0.001) by the inclusion of 150 and 300 g sDDGS/kg diet. While protease individually improved (P < 0.01) methionine digestibility, independent of sDDGS inclusion, an admixture of xylanase and protease did not result in further improvement in amino acid digestibility. Addition of xylanase reduced (P < 0.05) the concentration of insoluble non-starch polysaccharides (NSP) in the ileum. Noticeably, the response of birds to xylanase supplementation on the concentrations of arabinose, xylose and total insoluble NSP was compromised when xylanase and protease were added to the diet simultaneously. To conclude, despite lack of significant synergy, supplementation of xylanase and protease to the diets containing sDDGS was beneficial for the FCR and BWG of the birds, respectively.