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

This study evaluated whether β-mannanase systems incorporating additional glycoside hydrolase domains and accessory peptides provide functional advantages over conventional β-mannanase in broilers fed energy-reduced NSP-rich diets. This study evaluated the effects of positive control as basal diet (PC), negative control reduced metabolizable energy 120 kcal/kg in PC (NC), NC + 0.05% β-mannanase (M1), NC + 0.05% β-mannanase with upgraded glycoside hydrolase (M2), NC + 0.05% β-mannanase with upgraded glycoside hydrolase and accessory peptides (M3) on growth performance, nutrient digestibility, blood metabolites, carcass traits, and meat quality of broilers fed diets rich in non-starch polysaccharide (NSP). Results showed that β-mannanase supplementation (M2 and M3), but not conventional β-mannanase alone, synergistically increased (p < 0.05) digestive enzyme activity, and overall nutrient utilization. This increment translated into higher (p < 0.05) growth performance and feed conversion ratio. β-Mannanase supplementation also reduced (p < 0.05) intestinal viscosity, promoted endogenous protease activity, and increased (p < 0.05) the digestibility of key amino acids (AA) such as lysine, methionine, threonine, and valine. The M2 and M3 treatment lowered (p < 0.05) blood urea nitrogen levels, indicating more efficient protein utilization for growth. Furthermore, M2 and M3 supplementation increased (p < 0.05) thigh muscle proportions while reducing abdominal fat deposition, although no significant differences were observed in meat quality parameters (pH, water-holding capacity, shear force). Plasma AA levels remained unchanged, reflecting rapid utilization in protein synthesis and metabolism. Overall, these findings demonstrate that structural upgrading of β-mannanase rather than enzyme inclusion alone represents a distinct nutritional strategy to improve energy and protein utilization in broilers without negatively affecting meat physicochemical properties.