Effects of dietary β-mannanase supplementation on the additivity of true metabolizable energy values for broiler diets

Objective: This experiment was conducted to determine the effects of dietary β-mannanase on the additivity of true metabolizable energy (TME) and nitrogen-corrected true metabolizable energy (TME_n) for broiler diets.

Methods: A total of 144 21-day-old broilers were randomly allotted to 12 dietary treatments with 6 replicates. Five treatments consisted of 5 ingredients of corn, wheat, soybean meal, corn distillers dried grains with solubles, or corn gluten meal. One mixed diet containing 200 g/kg of those 5 ingredients also was prepared. Additional 6 treatments were prepared by mixing 0.5 g/kg dietary β-mannanase with those 5 ingredients and the mixed diet. Based on a precision-fed chicken assay, TME and TME_n values for 5 ingredients and the mixed diet as affected by dietary β-mannanase were determined.

Results: Results indicated that when β-mannanase was not added to the diet, measured TME and TME_n values for the diet did not differ from the predicted values for the diet, which validated the additivity. However, for the diet containing β-mannanase, measured TME_n value was greater (p<0.05) than predicted TME_n value, indicating that the additivity was not validated.

Conclusion: In conclusion, the additivity of energy values for the mixed diet may not be guaranteed if the diet contains β-mannanase.