The positive effect of dietary synbiotic supplementation on fish exposed to bacterial infection has been poorly researched. A team of international researchers 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 eight 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. Synbiotic diet 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.
Researchers suggested that dietary synbiotic supplementation has the potential to improve antioxidant response and health welfare of barramundi.
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