Influences of indigenous isolates Pantoea agglomerans RCS2 on growth, proximate analysis, haematological parameters, digestive enzyme activities, serum biochemical parameters, antioxidants activities, intestinal morphology, disease resistance, and molecular immune response in juvenile's cobia fish (Rachycentron canadum)

Abstract

The fast expansion and high intensity of cobia culture or, better still, farming has resulted in diseases infestation and has been recognised as a significant evolving problem for cobia culture throughout its production cycle. This study explored the possible effects of dietary additives of indigenous Pantoea agglomerans RCS2 on growth, haematological parameters, biochemical blood indices, antioxidant enzyme activities, disease resistance, digestive enzyme activities, and molecular immune response in juvenile's cobia fish. After 70 days, the growth parameters (i.e., specific growth rate, weight gain, and final weight) and feed conversion ratio significantly improved (P < 0.05) compared to those fed diets without supplementation. Also, haematological parameters such as red blood cells, white blood cells, corpuscular haemoglobin concentration, mean corpuscular volume, haemoglobin, and Mean corpuscular haemoglobin were high significantly (P < 0.05) in supplemented groups. The serum blood biochemical indices aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, triglyceride, cholesterol, and glucose recorded no significant difference (P > 0.05) while globulin, total protein, and albumin were high significantly (P < 0.05) in supplemented groups as compared to the group without supplement. The current results displayed that the activities of superoxide dismutase, glutathione peroxidase, and catalase in the liver and head kidney were affected by dietary supplements of indigenous isolated microorganisms. An exceptionally low mortality rate was observed in the treatment groups than the group without supplemented diets when challenged with pathogenic bacteria. Similarly, light microscopy revealed an increase in the intestinal villus length in fish fed with the supplemented diet compared to those without supplements. In this study, the higher digestive enzyme activities show that supplemented bacteria isolates have impacted digestive enzyme secretion in juvenile cobia. Regarding the gene expression, Interleukin-1 Beta (IL-1β), Tumour necrosis factor α (TNFα), and Interleukin-8 (IL-8) were all up-regulated by indigenous isolates. The current results show that the dietary additive of indigenous P. agglomerans RCS2 could constitute a treasured nutritional approach in the path of a sustainable cobia aquaculture. The fish immune responses enhancement and the gut morphology are vital in enhancing growth, absorption of nutrients, and disease resistance; hence the results in the present study are essential outcomes for the development and competitive aquaculture sector.