Oregano (Origanum vulgare), St John's-wort (Hypericum perforatum), and lemon balm (Melissa officinalis) extracts improved the growth rate, antioxidative, and immunological responses in Nile tilapia (Oreochromis niloticus) infected with Aeromonas hydrophila

Abstract

© 2020 The Author(s) The present study was designed to evaluate the effects of ethanolic extracts of Hypericum perforatum (HP), Origanum vulgare (ORG), and Melissa officinalis (MOF) on Nile tilapia (Oreochromis niloticus) juveniles. Fish (16.92 ± 0.28 g) were randomly divided into seven groups fed on diets with 0 % (CTR), and two levels (0.2 % and 0.5 %) from each plant extract for 60 days. Final body weight, weight gain %, specific growth rate, and feed conversion ratio were significantly improved in the groups fed with ORG and MOF at 0.5 % (P < 0.05). Moreover, ORG 0.5 % and MOF 0.5 % groups showed a significant increase in RBCs and WBCs counts as well as the hematocrit and hemoglobin values (P < 0.05). Besides, significant enhancement was noticed in the levels of intestinal digestive enzymes in the MOF 0.5 % group (P < 0.05). Activities of hepatic superoxide dismutase, glutathione peroxidase, catalase were significantly improved, meanwhile, the hepatic malondialdehyde levels were significantly decreased in all groups fed on phytogenic diets compared to the CTR group (P < 0.05). Furthermore, ORG 0.5 % and MOF 0.5 % groups showed a significant increase in serum total protein, and alternative complement activity (ACH50) (P < 0.05). Attractively, serum lysozyme levels were significantly increased while serum endotoxin values decreased in all groups fed on phytogenic diets. Furthermore, the MOF 0.5 % group showed the highest activities of skin mucus lysozyme, ACH50, and protease (P < 0.05), meanwhile mucosal total immunoglobulins were the highest in ORG 0.5 % and both levels of MOF. ORG 0.5 % and MOF 0.5 % groups showed the highest protection levels of fish following challenge with pathogenic Aeromonas hydrophila. Conclusively, this comparative study showed that both ORG and MOF extract at a 0.5 % level can effectively improve the growth, health, and immune status of Nile tilapia juveniles.