Synbiotic feed supplementation improves antioxidant response and innate immunity of juvenile barramundi, Lates calcarifer subjected to bacterial infection

The positive effect of dietary synbiotic supplementation on fish exposed to bacterial infection is poorly researched. The present study addressed the knowledge gap of dietary supplementation of Lactobacillus casei and garlic, Allium sativum, termed as synbiotic on the growth performance, lipid utilization, antioxidant activities, skin mucosal status, cytokine gene expression and intestinal epithelial responses following Vibrio harveyi infection in juvenile barramundi, Lates calcarifer. Juvenile barramundi with an initial weight of 9.16 +/- 0.08 g were randomly allocated into 8 tanks of 300 L capacity each at a density of 20 fish per tank. The quadruplicate groups were fed either a non-supplemented control diet or the same control diet supplemented with 1% of garlic powder and 1% of L. casei (109 CFU/mL) for 56 days. Results indicated that although the synbiotic supplemented diet did not produce any significant improvement in growth rate and feed utilization, lipid utilization and glutathione peroxidase activity were improved (P < 0.05). Synbiotic diet also reduced the intraperitoneal adipocyte cells size and increased the number of skin mucin cells. TEM micrographs showed an enhanced microvilli length with a normal intestinal morphological pattern in synbiotic fed fish compared to a leaky intestinal tight junction in the control when fish are subjected to V. harveyi infection. In addition, a significant improvement of the expression of immune responsive genes were found in synbiotic fed fish when compared to control. Overall, the results indicate that dietary synbiotic supplementation has the potential to improve antioxidant response and health welfare of barramundi.

Automated summary

The study found that dietary synbiotic supplementation has a positive effect on fish exposed to bacterial infection, improving lipid utilization, antioxidant activities, and overall health welfare of the fish.