Impact of mannanase on broiler performance, intestinal health, and energy utilization with varying soybean meal levels

Mannanase specifically degrades mannan, increases the efficiency of energy utilization, and improves intestinal health in broilers. The interaction effects between mannanase and soybean meal (SBM) have not been extensively explored. Therefore, the present study aimed to determine effects of adding mannanase to diets with different SBM content on broilers, and to explore interaction effects between mannanase and SBM. This study was conducted on Arbor Acres broilers. Under low-energy conditions (metabolizable energy reduced by 50 kcal/kg), a 3 × 2 factorial design was used with three SBM content diets (control group, 50%, or 25% of the SBM content of control) and with two levels of mannanase (0 or 100 mg/kg) respectively. In experiment 1, growth performance and intestinal health were determined. Experiment 2 measured energy metabolism in broilers by respiratory calorimetry, while feces were collected to determine nutrient digestibility. Results indicated that low SBM diets supplemented with degossypolled cottonseed protein and corn gluten meal significantly reduced broiler growth performance during d 0−42. However, mannanase supplementation in diets containing 35.66% and 17.83% SBM significantly improved growth performance from d 0 to 21, reduced respiratory quotient at 21 d, and improved intestinal health (p < 0.05). In the 35.66% SBM diet, mannanase also enhanced energy metabolism by improving nitrogen retention and protein energy utilization (p < 0.05). However, mannanase showed limited efficacy when SBM content was reduced to 8.92%. Microbiological analyses showed that mannanase significantly reduced Escherichia coli and promoted 2-Oxocarboxylic acid metabolism in cecal microbes. In conclusion, there was a reciprocal relationship between mannanase and SBM content, with mannanase still exerting the above beneficial effects at the SBM level of 17.83%.