Weight gain and health are determining factors in the success of catfish production. After a three-month pond study, fish that were fed ONE Current™ (a commercial feed additive by Strong Animals® , a brand of Ralco® , containing a proprietary blend of oregano, thyme and cinnamon essential oils, Actifibe® Prebiotic and Yucca schidigera ) test diet demonstrated significantly greater weight gain than fish fed a control diet. When transferred into tanks and immersion exposed to Edwardsiella ictaluri , fish that were fed the test diet demonstrated significantly higher survival than fish fed the control diet.
Intestinal innate immune cells are essential for communicating with commensal bacteria and killing gut pathogens. Therefore, leukocytes were isolated from the gut and anterior kidney tissues of test diet fed fish and from fish fed the control diet, and characterized using monoclonal antibodies for dendritic cells, neutrophils, cytotoxic cells and macrophages. When visualized by flow cytometry, there was no significant difference between the number of cell types from fish fed the test diet or the control diet. However, when incubated with bacteria, macrophages and cytotoxic cells from fish fed the test diet phagocytosed or bound significantly higher numbers of bacteria than the same cell type from fish fed the control diet, indicating these cells were more efficient at phagocytosing and binding bacteria than cells from the control diet fed fish. Significantly higher reactive nitrogen species (RNS) production and significantly higher lactate dehydrogenase activity (LDH) were also demonstrated by adherent leukocytes from the test diet fed fish.
Gut morphology underlies nutrient absorption. A greater surface area of the gut will lead to greater nutrient absorptive capabilities. Histological examination of the gastrointestinal tract demonstrated significantly greater mucosa, submucosa and lamina propria height after month 2, and greater villi height and width after months 2 and 3 in the fish fed the test diet. Higher RNS and LDH production, and higher bacterial phagocytosis by macrophages and binding by cytotoxic cells from test diet fed fish contributed to higher survival. Based on the findings of this study, use of ONE Current™ supplemented feed in catfish production increases growth, improves health, and minimizes infectious disease losses.