Exogenous α-amylase supplementation reduces the variability of ileal digestible energy in broiler chickens fed complete diets with maize batches of variable protein solubility

Abstract

This study evaluated the relationship between salt-soluble protein (SSP) of maize and the apparent ileal digestibility (AID) of complete diets in response to exogenous α-amylase supplementation in broiler chickens. Samples of 12 maize batches originating from the mid-north and northeast of China were analyzed for SSP. Six of the 12 sources of maize with a wide variation of SSP (from 21.1 % to >50 %) were selected. Six maize-soybean meal basal diets were formulated, including each source of maize with or without the addition of α-amylase (Ronozyme® HiStarch; DSM Nutritional Products). A total of 960 day-old male Arbor Acres Plus broiler chickens were randomly allocated to 12 treatments with 8 replicates per treatment in wired cages and fed experimental diets in 2 phases (d 1−14; d 15−28). At d 28, 4 birds selected from each cage were euthanized for evaluation of apparent ileal digestibility (AID) of starch and energy. The addition of α-amylase reduced the feed conversion ratio (FCR) of chickens from 1 to 28 d (1.407 vs. 1.426) compared to the basal diets across maize batches, particularly from 1 to 7 d (1.049 vs. 1.078). An interaction between maize batch and α-amylase supplementation on FCR was detected only at 7 d, when the batch with the lowest SSP exhibited the greatest response to α-amylase. Neither a main effect of α-amylase nor an interaction with maize batch on AID of starch were detected (P > 0.05). Nonetheless, α-amylase supplementation increased ileal digestible energy (IDE) from 12.21 to 12.50 MJ/kg dry matter across maize batches. These increments were mainly driven by the maize batch with the lowest SSP. α-amylase supplementation reduced the variability of IDE from a coefficient variance (CV)=5.2 % to a CV=0.7 % across maize batches. Interestingly, there was a strong negative correlation (r<-0.95; P < 0.001) between the initial IDE of maize and the IDE response to α-amylase, and a less strong correlation between SSP and the IDE response to α-amylase (r=-0.78, P = 0.07). SSP was not a predictor of starch digestibility at this age. Dietary α-amylase supplementation has the potential to significantly reduce the variability in the energy value of maize-based diets in commercial poultry production by improving the nutritional value of poorly digestible maize.