Effects of enzyme combinations on apparent metabolizable energy of corn-soybean meal-based diets in broilers

Corn and soybean meal (SBM) are high-quality feed ingredients for broiler diets. Antinutritive factors in SBM, such as protease inhibitors and lectins, are successfully inactivated by heat treatment. However, the nutritive value of these ingredients also depends on the amount of indigestible carbohydrates, in particular the amount of oligosaccharides and nonstarch polysaccharides (NSP). Despite the fact that such diets are low in indigestible carbohydrates, it has been suggested that the inclusion of exogenous feed enzymes to such diets could improve nutrient availability and, subsequently, improve energy digestibility. Four consecutive AME bioassays were conducted to investigate the effects of three single-activity enzyme products, two multi-activity enzyme preparations, and a commercially available enzyme product added to a corn-SBM-based broiler diet. None of the evaluated enzyme combinations successfully improved the performance of 3- to 4-wk-old broiler chickens. However, in experiments 1 and 2, when enzymes were included in a lower-energy corn-SBM basal diet, the combination of pectinase, protease, and amylase significantly improved AME(n) in comparison to the unsupplemented basal diet. Subsequent experiments with a higher energy and protein basal diet failed to show the same improvement when enzymes were added. Results of this study indicated that although enzyme addition to corn-SBM-based basal diets can significantly improve AME(n), the success of such improvement depended greatly on the raw ingredients available at the time.