Effects of different combinations of Bacillus on immunity and antioxidant activities in common carp

Bacillus can not only improve the ecological environment of aquaculture water, but also improve the immunity of aquaculture animals, inhibit the reproduction of pathogenic microorganisms and reduce the incidence of disease. The present study represented the effect of different combinations of Bacillus on immunity and antioxidant activities in common carp. A total of 240 fish were randomly divided into four groups: control group (basal diet), experimental group I (add B. subtilis), experimental group II (add B. subtilis and B. licheniformis), and experimental group III (B. subtilis, B. licheniformis, and B. cereus). Compared with the control group, the carp in experimental group II displayed a significantly elevated phagocytic percentage (up to a 20.2% increase; P < 0.05), phagocytic index (up to a 41.5% increase; P < 0.05), serum immunoglobulin M (up to a 26.1% increase; P < 0.05), serum lysozyme activity (up to a 21.9% increase; P < 0.05), intestinal mucosal secretory immunoglobulin A content (up to a 53.1% increase; P < 0.05), and peripheral blood lymphocyte proliferation ratio (up to a 32.8% increase; P < 0.05). Further analysis of liver antioxidants showed that, compared with the control group, carp in experimental group II displayed elevated superoxide dismutase (69.4%; P < 0.05), glutathione peroxidase (25.4%; P < 0.05), catalase (76.4%; P < 0.05), total antioxidant (41.1%; P < 0.05), maleic dialdehyde (28.9%; P < 0.05), and glutathione (35.6%; P < 0.05) activities. There was no significant difference between the experimental group I and the experimental group III (P > 0.05). Our results indicated that dietary Bacillus enhanced the performance of the common carp immune response and that a mixture of strains elevated the antioxidant ability.