Immune Responses to Vibrio anguillarum in Yellowtail Kingfish, Seriola lalandi, Fed Selenium Supplementation

Abstract

Effects of dietary selenium (Se) on immune competence of yellowtail kingfish, Seriola lalandi, were investigated. The fish were fed one of the three experimental diets including a control diet without Se supplementation and two diets supplemented with Se from Se-yeast (Selplex®) at 2 and 4mg/kg. After feeding for 6 wk, the fish were challenged by injecting Vibrio anguillarum and observed for 2wk. Dietary Se had no effect on feed intake, feed conversion ratio, and survival over the course of 6-wk feeding; however, it significantly increased weight gain and Se content in muscle. Following the bacterial infection, the immune-stimulating effects of Se were observed in antibody, lysozyme, and bactericidal responses, and there was a corresponding increase in survival and hematocrit by Se. Under infectious condition, antioxidant capacity of fish as measured in term of resistance of red blood cells to peroxidation and glutathione peroxidase activity also increased by supplementation of Se. Liver necrosis and kidneymelano-macrophages were only seen in surviving fish fed the control diet after the challenge. Furthermore, there was evidence of myopathy in fish fed the diet without Se supplementation. This study suggests that Se, supplemented at 2 or 4mg/kg, can improve growth and health of yellowtail kingfish.