Performance and nutrient digestibility of broilers fed barley-based diets supplemented with amylase

This study evaluated the effects of exogenous amylase supplementation in barley-based diets for broiler chickens. Two experiments (Exp. 1 and 2) were conducted, in which 11-to-33-d-old broilers were assigned to two dietary treatments (with or without amylase at 81 kilo-novo units/kg diet) in a randomized design. Exp. 1 used 352 male broilers (8 replicates of 22 birds) and a low-viscosity normal hulled barley, while Exp. 2 utilized 484 female broilers (11 replicates of 22 birds) and a normal hulled cultivar of high-viscosity. All diets in both trials were supplemented with phytase and a xylanase and β-glucanase complex. In Exp. 1, amylase tended to improve feed conversion ratio (P < 0.1) and increased AID of crude protein (CP) (P < 0.05) at 33 d of age but had no effect on AID of starch. In Exp. 2, no effects of amylase were observed on growth performance, AID of starch and CP, or relative organ weights. Overall findings from both Exp indicate that amylase supplementation can increase CP digestibility of barley-based diets depending on intrinsic viscosity, which may then improve performance. High starch digestibility observed in diets without amylase explains the lack of enzyme effect and suggests the investigated barleys caused no major detrimental effects to nutrient utilization, although the use of high-viscosity barley in Exp. 2 led to lower AID of starch and CP than Exp. 1. The use of a fiber-degrading enzyme likely enhanced starch utilization, leaving limited room for improvements with amylase for broilers at this age.