The economic backdrop of the study is stark. Feed represents more than half of total broiler production costs, and as corn and soybean meal prices climb, producers are increasingly turning to alternative raw materials. The problem is that many of these alternatives are rich in non-starch polysaccharides, or NSP, complex plant carbohydrates that monogastric animals such as chickens cannot efficiently digest. Soluble NSP, particularly β-mannans found in soybean meal and palm kernel meal, dissolve in the gut and dramatically increase the viscosity of intestinal contents. This thickened digesta slows the diffusion of digestive enzymes toward their substrates, reduces nutrient absorption, and ultimately depresses growth and feed efficiency.

β-Mannanase has long been deployed as a countermeasure. The enzyme cleaves the β-1,4-mannosidic linkages in galactomannan backbones, breaking down viscous NSP and releasing nutrients physically trapped within plant cell walls. Previous research has also indicated that β-mannanase can reduce the impact of trypsin inhibitors in soybean meal by supporting endogenous protease activity. However, conventional commercial products typically consist of single-domain enzymes, and the Korean team hypothesized that incorporating additional glycoside hydrolase domains and accessory peptides could extend the enzyme’s functional reach, improving stability through the acidic proventriculus and gizzard and maintaining activity in the near-neutral small intestine where most nutrient absorption occurs.

To test this, the researchers allocated 300 day-old broilers to five dietary treatments: a positive control basal diet, a negative control with metabolizable energy reduced by 120 kcal/kg, and three enzyme-supplemented versions of the reduced-energy diet. The first enzyme (M1) was a conventional β-mannanase produced by fermentation with Bacillus subtilis, with an activity of approximately 800,000 U/kg. The second (M2) incorporated upgraded glycoside hydrolase functionality, and the third (M3) added accessory peptides designed to support enzyme-substrate interaction and gastrointestinal stability. The upgraded products were manufactured through optimized fermentation, with temperature modulated between 40 and 60 °C and pH between 5 and 6, to maximize enzyme secretion and consistency under feed manufacturing conditions.

In vitro characterization revealed meaningful differences among the three products. At pH 3.0, the conventional M1 enzyme retained relatively high activity, while the upgraded M3 showed a marked reduction. As pH rose to 6.0, however, the picture reversed: M3 and M2 demonstrated the highest relative activities, ranging from roughly 70 to 80 percent, while M1 declined. At pH 7.2, both upgraded enzymes significantly outperformed the conventional product. Thermal profiling showed that all three enzymes retained more than 80 percent activity at 30 °C, but at 60 °C the conventional M1 proved more heat-tolerant, a property potentially useful during feed pelleting yet apparently less decisive under living digestive conditions. Pepsin digestion assays further showed that M2 and M3 resisted proteolytic degradation better than the control diets, suggesting the upgraded enzymes could survive the hostile environment of the upper digestive tract.

The in vivo results were striking. Final body weight was significantly higher in the positive control and M3 groups compared with the unsupplemented reduced-energy negative control, and during the final phase, weight gain was higher in the positive control and M3 treatments while feed conversion ratio was lower in all enzyme-supplemented groups. Notably, feed intake did not differ among treatments, indicating that the performance benefits stemmed from improved nutrient utilization rather than simply eating more. In practical terms, the upgraded enzymes allowed birds to extract more energy and protein from a diet deliberately stripped of 120 kcal/kg, effectively recovering much of the nutritional value that NSP-rich ingredients would otherwise lock away.

Digestibility measurements reinforced this interpretation. Dry matter digestibility was higher with M2 and M3 than in the negative control, and crude protein digestibility in the M3 group exceeded both control diets. Apparent ileal digestibility of the key limiting amino acids lysine, methionine, and threonine was significantly improved by M2 and M3, while valine digestibility rose with all three enzyme products. Digesta analysis using ELISA-based assays showed elevated trypsin activity in all enzyme-supplemented groups and higher protease concentrations with M2 and M3, pointing to a secondary stimulation of the birds’ own digestive machinery. The researchers suggest that by dismantling anti-nutritional NSP barriers, the exogenous enzymes improved nutrient signaling within the gut, prompting greater endogenous enzyme secretion.

Metabolic markers told a consistent story. Blood urea nitrogen, an indirect indicator of protein metabolism and nitrogen balance, was significantly lower in the M2 and M3 groups than in both controls and the conventional enzyme group, consistent with more efficient incorporation of dietary amino acids into body tissue and reduced deamination. Jejunal digesta viscosity dropped significantly in all enzyme-supplemented groups, confirming the primary mode of action of β-mannanase in degrading soluble NSP. Plasma amino acid concentrations, however, remained unchanged across treatments, which the authors attribute to tight homeostatic regulation of circulating amino acid pools; when combined with improved growth, the pattern suggests enhanced post-absorptive utilization rather than accumulation in the bloodstream.

Carcass evaluation added a further dimension. The negative control group showed the lowest thigh muscle proportion, while the positive control and the two upgraded enzyme treatments achieved the highest values. Abdominal fat deposition was highest in the full-energy positive control group, implying that enzyme supplementation supported lean tissue deposition without the fat accretion associated with higher dietary energy. Dressing yield, breast muscle, drumstick, wing, and organ weights were unaffected, and critically, no significant differences emerged in meat quality parameters including pH, water-holding capacity, cooking loss, or shear force, indicating that the enzymatic intervention improved efficiency without compromising the physicochemical properties that consumers and processors care about.

The study’s authors are careful to note its limitations: only a single level of energy reduction and enzyme inclusion was tested, and mechanistic analyses of gut microbiota, intestinal morphology, and fermentation metabolites were not performed. Dose-response studies and microbiome sequencing could clarify how the accessory peptides in M3 enhance enzyme-substrate affinity or protect against proteolytic degradation. Nevertheless, the central conclusion carries weight for a global poultry sector under pressure to cut costs and reduce the environmental footprint of production. If structurally upgraded enzyme systems can recover 120 kcal/kg of dietary energy without sacrificing performance, carcass composition, or meat quality, feed formulators gain a powerful new lever, one that depends not on feeding more enzyme but on designing it better.

Subject of Research: Effects of structurally upgraded β-mannanase enzyme supplementation on nutrient utilization and growth performance of broilers fed energy-reduced, non-starch polysaccharide-rich diets

Article Title: Dietary β-mannanase supplementation and its effect on nutrient utilization and performance in broilers fed energy-reduced diets

Article References: Choi, S. D., Tajudeen, H., Mun, J. Y., Park, S. A., Hosseindoust, A., Neves Silvestre, P., Lee, S. S., & Kim, J. S. (2026). Dietary β-mannanase supplementation and its effect on nutrient utilization and performance in broilers fed energy-reduced diets. Food Science of Animal Resources, 46(1), Article 68. https://doi.org/10.1007/s44463-026-00068-7

Image Credits: AI Generated

DOI: 10.1007/s44463-026-00068-7

Keywords: β-mannanase, broilers, non-starch polysaccharides, feed enzymes, nutrient digestibility, energy-reduced diets, poultry nutrition, amino acid digestibility, feed conversion ratio, glycoside hydrolase, intestinal viscosity, carcass traits