Lemon, Citrus aurantifolia, peel and Bacillus licheniformis protected common carp, Cyprinus carpio, from Aeromonas hydrophila infection by improving the humoral and skin mucosal immunity, and antioxidative responses

Abstract

The role of dietary lemon peel (LM) and/or Bacillus licheniformis (BL) on the growth, immunity, and resistance against Aeromonas hydrophila in common carp, Cyprinus carpio was investigated in this study. LM and BL were included in diets at 0% (T0), 108 CFU/g BL (T1), 1.5% LM and 108 CFU/g BL (T2), and 3% LM and 108 CFU/g BL (T3). Fish fed with T1, T2, or T3 had higher weight gain, specific growth rate, white blood cells count, and blood total protein with lower feed conversion ratio than T0 group (p <.05). The albumin increased significantly (p <.05) in fish fed both BL and LM (T3). The serum superoxide dismutase (SOD), catalase, lysozyme, and bactericidal activities were significantly increased in fish fed both BL and LM (T2 and T3), while serum glutathione peroxidase increased in fish fed BL (T2) (p <.05). Fish fed T1, T2, and T3 diets displayed higher SOD and lower malondialdehyde than fish fed T0 (p <.05). After the A. hydrophila challenge, the mortality rate was significantly lower in T1, T2, and T3 groups than the T0 group (p <.05). The obtained results revealed that LM and BL could be used to increase resistance against A. hydrophila infection in carp. However, further field studies should be performed to confirm the obtained results.