Modulatory effects of fenugreek seeds powder on the histopathology, oxidative status, and immune related gene expression in Nile tilapia (Oreochromis niloticus) infected with Aeromonas hydrophila

Abstract

The present trial investigated the effects of dietary fenugreek on the histopathology, oxidative status, and immune-related gene expression in Nile tilapia (Oreochromis niloticus) (15 ± 0.5 g) infected with Aeromonas hydrophila. Fish were fed two diets with or without fenugreek supplementation at 3%. The trial was lasted for 8 weeks then fish were divided into four groups; the first and fourth groups were intra-peritoneally injected with phosphate buffer saline (PBS) while the second and third groups were challenged with sublethal dose of A. hydrophila. At 6 h, 24 h and 1-week post challenge, several serum immune and immune-related gene expressions and antioxidant defense parameters as well as the histopathological alterations were evaluated. The results indicated that administration of fenugreek supplemented diets could significantly increase the growth performance parameters and decreased the feed conversion ratio as compared to the non-supplemented groups (P < 0.05). Furthermore, fish fed fenugreek supplemented diets showed improved immune (lysozyme, immunoglobulin, and respiratory burst activity) and antioxidant parameters (superoxide dismutase and glutathione peroxidase and malondialdehyde) in 6 h, 24 h and 1-week post challenge (P < 0.05). Additionally, fenugreek upregulated the immune-related gene expressions in liver and kidney (IL-1β and TNF-α) and reduced the blood aspartate aminotransferase (AST) and alanine aminotransferase (ALT) indicating the protective role for the hepatic tissue (P < 0.05). The histopathological images of A. hydrophila infected groups revealed damage in intestine, spleen, hepatopancreas and kidney which exaggerated with time, but the infected groups fed on fenugreek diet showed significant alleviation of damage of intestine, hepatopancreas, spleen and kidney. The results of challenge test showed that administration of fenugreek supplemented diets significantly increased tilapia resistance (P < 0.05); the highest survival rate, was observed in the third group. Fish fed 3% fenugreek supplemented diets exhibited increased immune response and antioxidant capacity compared other groups (P < 0.05). The present results confirmed the beneficial effects of fenugreek as a natural alternative immunostimulant for Nile tilapia aquaculture.