Effects of beta-mannanase supplementation on growth performance, digestibility, intestinal morphometry, and cecal microbiota in broiler chickens

The β-mannans present in the fibrous portions of vegetables are associated with increased gastrointestinal viscosity, delayed gastric emptying, and reduced nutrient digestibility. Dietary supplementation with exogenous β-mannanase could offer an alternative to mitigate the adverse effects of this anti-nutritional factor, given its resistance to most chemical and physical processes used for treatment and inactivation. This study evaluated the effects of β-mannanase supplementation on growth performance, intestinal morphometry, cecal microbiota, and digestibility in broiler chickens. Treatments were as follows: PC positive control (basal diet), NC negative control (basal diet with a reduction of 36 kcal/kg of metabolizable energy), and NC+βm: negative control with the addition of β-mannanase. The β-mannanase supplementation (NC+βm) resulted in greater digestible energy from d 0 to 21 compared to PC and NC. At d 22, NC+βm exhibited greater digestible energy (P = 0.043) and villus-to-crypt ratio (P = 0.007) compared with PC in the duodenum, suggesting enhanced nutrient absorption. At 43 d, broiler chickens on NC+βm had lower (P < 0.001) villus height and crypt depth compared with PC and NC in the duodenum. Across all indices, alpha diversity of the cecal microbiota, except for Simpson's index and Pielou's evenness, was greater (P < 0.01) in 43 d on the β-mannanase diet than at 22 d, indicating a potential positive modulation of gut microbial ecology over time. Based on the results, β-mannanase supplementation can be considered a nutritional strategy for broiler chickens, with positive effects on intestinal morphometry, cecal microbiota, and the apparent digestibility of gross energy.