Researchers tested the enzyme's effectiveness in a 3×2 factorial experiment, combining different SBM concentrations and mannanase doses under low-energy conditions. The findings show that mannanase improved feed conversion ratios, reduced gut inflammation, and enhanced microbial balance, especially in diets containing 17.83% or more SBM.
Soybean meal (SBM) is a primary protein source in poultry diets, but it contains anti-nutritional factors—particularly mannans—that hinder digestion and stimulate immune responses, leading to energy loss. Mannanase, an enzyme that breaks down β-1,4-mannosidic bonds in mannans, can reduce intestinal viscosity and enhance nutrient absorption. While mannanase has shown individual benefits, its interaction with varying SBM levels had not been thoroughly studied. Given that reducing metabolizable energy by just 50 kcal/kg can impair broiler growth and gut integrity, this study sought to determine whether mannanase could mitigate those negative effects—especially in diets with partial or minimal SBM content.
A study (DOI: 10.48130/animadv-0025-0009) published in Animal Advances on 07 May 2025 by Yuming Guo's team, China Agricultural University, points to a promising nutritional strategy for poultry producers facing cost pressures or feed ingredient limitations.
To evaluate the impact of mannanase supplementation under varying soybean meal (SBM) levels in energy-restricted broiler diets, researchers conducted a controlled 3×2 factorial experiment using Arbor Acres broilers. Diets were formulated with three SBM inclusion rates (35.66%, 17.83%, and 8.92%) and two mannanase levels (0 or 100 mg/kg), all under a metabolizable energy deficit of 50 kcal/kg. Growth performance, nutrient digestibility, energy metabolism, intestinal health, gene expression, and microbiota composition were comprehensively assessed.
The results revealed a significant interaction between mannanase and SBM content. Mannanase supplementation improved growth performance metrics such as body weight and feed conversion ratio (FCR), particularly in the 35.66% and 17.83% SBM groups. Respiratory metabolism assessments showed reduced oxygen consumption and carbon dioxide output, increased nitrogen retention, and decreased nitrogen excretion with mannanase addition. Energy metabolism was enhanced as evidenced by higher retained energy (RE), net energy (NE) values, and improved protein energy utilization, especially when SBM was maintained at 35.66%. Nutrient digestibility also benefited from mannanase, with increased apparent total tract digestibility (ATTD) of crude protein and key amino acids. Intestinal health improvements included reduced jejunal chyme viscosity, enhanced villus height and tight junction gene expression (e.g., Claudin-1, Occludin), and decreased serum markers of barrier dysfunction (D-LA, DAO, ET). Mannanase also suppressed inflammatory gene expression (IL-1β, IL-6, NF-κB) and improved anti-inflammatory profiles in the ileum. Microbial analysis showed a reduction in Escherichia coli and pathogenic genera, along with functional shifts in microbial metabolism, such as increased 2-oxocarboxylic acid pathways. These benefits, however, diminished when SBM content fell to 8.92%, suggesting a threshold for mannanase efficacy dependent on substrate availability.
These findings have important implications for poultry production systems seeking to reduce costs or soybean dependence without sacrificing performance. Mannanase supplementation enables better nutrient utilization, compensates for lower energy inputs, and supports gut health—key factors for efficient broiler growth. Feed formulators may strategically include mannanase in diets with moderate soybean meal levels (≥17.83%) to maintain performance metrics while managing ingredient variability or cost pressures. This enzyme-based strategy could reduce reliance on high-energy inputs and improve environmental sustainability by enhancing feed conversion efficiency.
