Dietary supplementation with β-mannanase-producing Bacillus velezensis HF-14109 enhances growth performance, antioxidant status, immune response, and intestinal health in Common Carp

ABSTRACT Objectives Mannan, an antinutritional factor in plant-based aquafeeds, impedes nutrient absorption. How to reduce the antinutritional factors simply and efficiently in plant fish meal and improve its utilization is one of the difficulties in the current research. This study investigated the effects of dietary supplementation with β-mannanase-producing Bacillus velezensis HF-14109 (HF-14109) in Common Carp Cyprinus carpio. Methods Juvenile Common Carp (35.2 ± 0.5 g initial weight) were stocked in triplicate tanks (10 fish per tank) within a recirculating aquaculture system and fed one of four experimental diets (0, 107, 108, and 109 CFU/g HF-14109, respectively). Results Compared with the control group (0), the HF-14109 groups exhibited elevated digestive enzyme (β-mannanase, lipase, and pepsin) activity in gut; increased final body weight, weight gain rate, specific growth rate, and antioxidant enzyme activities (glutathione, superoxide dismutase, catalase); and reduced malondialdehyde. Dietary β-mannanase-HF-14109 significantly (1) elevated alkaline phosphatase, high-density lipoprotein, and lysozyme levels; (2) decreased aspartate aminotransferase, alanine aminotransferase, cholesterol, triglyceride, and pro-inflammatory cytokines (TNF-α, IL-1β, IL-6); and (3) enhanced anti-inflammatory markers (IL-10, TGF-β). The inclusion of β-mannanase-HF-14109 improved the intestinal morphology of Common Carp, including thickened walls and elongated villi; increased the relative abundance of Firmicutes, Bacteroidota, and Fusobacteria; and reduced the relative abundance of Proteobacteria relative to the control. Conclusions These findings highlight HF-14109 as a multifunctional probiotic for sustainable aquaculture.