Abstract
Nutrient availability is critical for the development of poultry digestive function and immune responses. Carbohydrase formulations, containing alpha-galactosidase (CAG) enzyme with specificity for galacto-oligosaccharides fromsoybean meal (SBM), have been shown to increase dietaryMEin monogastric diets. This exploratory study aimed at evaluating the effect of CAG on the growth performance and humoral immunity of broilers fed corn-SBMdiets with varying energy density. A total of 640 male 1-day-old chicks were allocated at random to one of 64 floor pens, with 10 birds each. Replicateswere assigned to a 432 factorial experimental design. Four dietary energy density levels were formulated, namely control and with a 270, 2100, and 2120 kcal/kg of feed ME downspecification to the control. Each of these diets was treated with 2 levels of CAG supplementation, either none (2) or at a dose of 200 g/tonne (1). Growth performance was determined over a 35-D period. At the end of the study, carcass processing parameters, organ weight, and dimensions of the intestine were determined in 1 randomly selected bird per replicate. Humoral immunity was measured by quantification of antibody titers to Newcastle disease vaccination, in 1 bird per replicate, at 21 and 35 d of age. Dietary ME had a significant effect on BW and feed conversion ratio (FCR) (P < 0.05). Regression analysis confirmed differences in the linear response of CAG groups (2 or 1) in terms of elevation (P < 0.05) for BW gain and FCR. Significant interaction of the main effects confirmed that CAG maintained carcass dressing percentage equivalent to the control diet (P < 0.05). CAG increased antibody titers of broilers at 35 d, irrespective of the dietary energy density (P < 0.001). In conclusion, the impact on broiler growth performance from feeding low-energy-density diets can be ameliorated with a CAG enzyme.