Effects of Dietary β-Mannanase Supplementation on Growth Performance, Lipid Fraction Contents, and Physiological Responses in Broiler Chicks

This experiment was conducted to evaluate the dietary effects of β-mannanase on growth performance, cecal ammonia concentration, lipid fraction contents and physiological responses in broiler chicks. A total of nine hundred 1 d old Ross male broiler chicks were assigned to six groups arranged in a 3 × 2 factorial of three levels of energy and CP [standard energy + standard CP (HEHP), 75 kcal/kg diet reduction in energy + standard CP (REHP), 75 kcal/kg diet reduction in energy + 1% reduction in CP (RERP)], with or without β-mannanase (0 or 0.05%). As dietary energy and CP decreased, growth performance also decreased. The growth and feed conversion ratio in chicks fed diets containing β-mannanase significantly improved. No significant differences were observed in the levels of serum enzymes and the relative weight and length of each fraction of small intestine among groups, except for the liver. The concentration of cecal ammonia in chicks fed diets containing β-mannanase was significantly lower than those of corresponding groups without β-mannanase. The levels of serum and hepatic lipid fractions were not influenced by supplementing β-mannanase to the diets. These results indicated that dietary β-mannanase may improve growth performance and utilization of dietary energy and protein in broiler chicks.