Antioxidative status, immune response, and disease resistance of Clarias gariepinus fed on Azolla pinnata and Moringa oleifera supplemented diets

Abstract

The current study aims to supplement fish feed with two plants (Azolla pinnata and Moringa oleifera) in order to combat the disease caused by Edwardsiella tarda bacterium. Four groups of African catfish, Clarias gariepinus, were set up: fish fed on supplementary feed at 5% Azolla pinnata and 5% Moringa oleifera/kg diet for groups 1 and 2, the positive control, group 3, and negative control, group 4, received non-supplemented diets. After a two-week feeding period, all groups (except group 4) received an intraperitoneal injection containing a lethal dosage of Edwardsiella tarda isolated from a local outbreak with LD₅₀ 3×10⁴. Non-specific immune parameters and antioxidant indicators were estimated at the serum level of all experimental fish before and after the Edwardsiella tarda challenge. Furthermore, tissue expression levels of some immune and antioxidant-related genes were evaluated in the spleens of experimental fish before and after the Edwardsiella tarda challenge. Results recorded that supplemented feed groups showed relative percent survival of 75% and 66.67% for groups 1 and 2 against Edwardsiella tarda with normal serum levels of aspartate aminotransferase and alanine aminotransferase hepatic enzymes. The high survivability was accompanied by elevated serum levels of the measured non-specific immune parameters and antioxidant indicators, particularly after challenge. Also, transcription analyses showed upregulation of expression levels of GPX, SOD1, IL-1β, and MHC-IA genes in the spleens of experimental fish, indicating enhanced innate immune response of Clarias gariepinus fed on supplementary feed at 5 % Azolla pinnata and 5 % Moringa oleifera / kg diet for two weeks.