This study investigates the possible effects of using Lactobacillus fermentum (LF) and/or ferulic acid (FA) in common carp (Cyprinus carpio) on some immunological parameters as well as resistance against Aeromonas hydrophila. Four diets were prepared including control diet and three diets supplemented with LF (108 CFU/g), FA (100 mg kg-1) or LF + FA (108 CFU/g + 100 mg kg-1). After 8 weeks, fish fed LF or/and FA had significantly higher final body weight, weight gain, and specific growth rate when compared to control group (P < 0.05). The feed conversion ratio of fish fed LF or/and FA were noticeably lower than control (P < 0.05). No alterations were observed in case of haematological parameters except red blood cells (RBCs), white blood cells (WBCs), hemoglobin (Hb), and hematocrit (HCT) which were significantly (P < 0.05) increased in fish fed FA or those fed both LF and FA. Also, the WBCs of fish treated with LF or/and FA were noticeably higher than control (P < 0.05). Feeding on LF and FA notably increased the serum total protein and albumin levels (P < 0.05). The serum respiratory burst and lysozyme activity were also enhanced (P < 0.05) in fish fed both LF or/and FA. In addition, evaluation of the serum antioxidant enzymes (catalase, glutathione peroxidase (GPX), and superoxide dismutase (SOD)) activity showed significant (P < 0.05) increase in fish fed FA or both LF and FA as compared to the control. Fish fed LF and FA supplemented diet had highest survival rate after experimental challenge with pathogenic A. hydrophila. The obtained results revealed that LF and/or FA can be used as beneficial feed additive to improve the immune responses and disease resistance in early stages of common carp culture.
Keywords: Aeromonas hydrophila; Common carp; Ferulic acid; Immune response; Oxidative status; Probiotics.
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