Mentha piperita powder enhances the biological response, growth performance, disease resistance, and survival of Oreochromis niloticus infected with Vibrio alginolyticus

Recently, medical plants have been widely used as replacements for antibiotics in disease treatment. Because of its multiple medicinal uses, peppermint (Mentha piperita, MP) is a common herbal remedy. In the present study, MP powder was used as a feed additive to assess growth performance; hematological; biochemical and immune parameters; intestinal histology; and interleukin 1β (IL-1β) gene expression, as well as protection against Vibrio alginolyticus infection in Oreochromis niloticus. O. niloticus (n = 120, 25.66 ± 0.16 g) were fed diets containing 0 (CTR), 2, 3, or 4% MP for 60 days. The results revealed that the inclusion of 2% MP significantly improved the growth indices, intestinal morphological parameters, and reduced the feed conversion ratio. The 2% MP treatment significantly (P < 0.05) increased hematological parameters (red blood cell (RBC) count, white blood cell (WBC) count, packed cell volume% (PCV%), hemoglobin) compared with those of the CTR (P < 0.05). Additionally, feeding fish 2% MP diets decreased the levels of cholesterol and LDL (low-density lipoprotein). There were significant increases in immune responses (serum protein and phagocytic activity and index) and non-significant increases in the expression of IL-1β in the 2% MP group comparing with the other groups and the CTR group (P < 0.05). At the end of the feeding trial (60 days), fish were challenged with a virulent strain of Vibrio alginolyticus and the results showed that the mortality rate decreased in the 2% MP treatment group, followed by the 3% and 4% MP groups. Overall, the results revealed that the dietary inclusion of 2% MP can exhibit growth-promoting and immunostimulant effects for sustainable aquaculture.