Protection of Vibrio harveyi infection through dietary administration of Pueraria thunbergiana in kelp grouper, Epinephelus bruneus

The present study determined the protection afforded by dietary administration with Pueraria thunbergiana extract in terms of mortality and innate immune response to Vibrio harveyi infection in kelp grouper, Epinephelus bruneus. The grouper was fed with 0% (control), 0.1%, 1.0%, and 2.0% supplementation diets at week 1, 2, and 4. All enriched diets significantly increased the weight gain (WG) from weeks 1 to 4 while specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER) did not change significantly when compared to the control. The white and red blood cells count, haemoglobin, haematocrite, lymphocytes, and monocytes significantly increased when fed with 1.0% and 2.0% supplementation diets against pathogen. Total protein content and albumin level significantly increased with 1.0% diet than when fed with 0.01% or 2.0% enriched diet. All the supplementation diets significantly enhanced phagocytic ratio and lysozyme activity from week 1 to 4 against pathogen. The phagocytic index, superoxide anion production, bactericidal activity, and anti-protease activity significantly increased in fish fed with 1.0% and 2.0% doses diets from weeks 1 to 4 as compared to the control, but not with 0.1% diet. The highest protection by means of lower cumulative mortality was recorded with 1.0% and 2.0% diets when compared to 0% and 0.1% diet. This study suggested that 1.0% and 2.0% supplementation diet significantly influence the growth, hematology, and enhance the innate immune system in kelp grouper, E. bruneus against V. harveyi.

► The present study determined mortality and innate immune response in kelp grouper.
► All enriched diets significantly increased the weight gain (WG) from weeks 1 to 4.
► The WBC, RBC, Hb, Ht, lymphocytes, and monocytes significantly increased against pathogen.
► All the diets significantly enhanced phagocytic ratio and lysozyme activity from week 1 to 4.
► The phagocytic index, superoxide anion production, bactericidal activity, and anti-protease activity significantly increased.