This study aimed to evaluate the effects of a proprietary admixture of carbohydrase enzymes on different sources (origin) of corn and soybean meal (SBM)-based diets on growth performance and apparent ileal digestibility (AID) of nutrients of broiler chickens. A total of 216 day-old chicks (Cobb 500) were equally distributed to 36 floor pens (9 replicates, 6 birds/pen), and the pens were allocated to 4 dietary treatments in a completely randomized 2×2 factorial arrangement. The treatments included: 2 corn and SBM sources as the main ingredients supplemented without (NC1 and NC2) or with enzymes (NC1+Enz and NC2+Enz). The diets were formulated in three phases (starter, d 0-14; grower, d 15-28; finisher, d 29-42), and all diets contained phytase in the background. Feed and water were provided ad libitum. The birds were housed in floor pens, and a standard commercial broiler rearing environment (temperature, humidity, and light) was managed. The body weight and feed intake were recorded at the beginning of trial and then on days 14, 28, and 42 to determine growth performance and feed conversion ratio (FCR). At 42d of age, ileal samples were collected to determine the AID of nutrients using the marker (TiO2) method. Data were subjected to multi-factorial analysis of variance and were compared among treatments using the MIXED procedure of SAS with a pen as the experimental unit. There was no effect of treatments on body weight (BW) and average daily gain (ADG) in the starter phase, but supplementation with enzymes increased (P <0.05) both BW and ADG during grower and finisher phases as well as the overall study period. Also, there was an interaction (P <0.05) between ingredient source and enzyme supplementation for BW, ADG, ADFI, and FCR in the finisher phase and ADG and ADFI in the overall study period. Enzyme supplementation significantly reduced (P <0.05) FCR in all stages of the study. There was a significant effect (P <0.05) of both the ingredient sources and enzymes on the AID of nutrients (DM, GE, and CP) as well as ileal AME, ileal AMEn, and N retention at ileum level. Also, a significant interaction between ingredient type and enzymes was found for N retention (P <0.05).
In conclusion, there was no notable effect of ingredient sources, but enzyme supplementation positively affected the growth performance parameters of broilers. As the source of corn and SBM influenced the effect of enzymes on nutrient digestibility and there was an interaction between ingredient source and enzyme supplementation, future work should use ingredients from different origins and explore reasons for this in order to further optimize the economic value of carbohydrases in corn/SBM-based diets for broilers.