Evaluation of the Dietary Effect of Hallabong Peel Oil on Growth, Hematological, and Immune Gene Expression in Rock Bream, Oplegnathus fasciatus Challenged with Edwardsiella tarda

In the present study we evaluated the dietary effect of Hallabong peel oil (HPO) on growth, disease resistance, and immune gene expression of rock bream, Oplegnathus fasciatus challenged with Edwardsiella tarda after a 4 week feeding trial with 5 treatments: control-C, probiotic–P, HPO (0.1%), HPO (0.5%), and P+HPO, diets. All fish groups were assessed for growth performance, innate immune parameters, serum biochemical profile, and immune gene expression in head kidney on 2nd, and 4th week, and 1st, 3rd and 7th day post infection with Edwardsiella tarda. Fish fed the HPO enriched diets showed increased growth performance with significantly decreased (P>0.05) mortality compared with the control and probiotic diet groups. The positive effects of HPO enriched diet were also found in all assessed innate immune and biochemical parameters which included increased respiratory burst and lysozyme activity, with significantly increased erythrocyte and leukocytes counts, increased serum protein, decreased glucose, triglycerides, cholesterol level in serum compared with control diet fed fish. Moreover, the probiotic bacterial count in the intestine of fish was enhanced with the HPO diet and the P+HPO diet compared to fish fed the probiotic diet. The head kidney of HPO enriched diet fed fish showed up-regulated expression of inflammatory cytokines genes such as TNFα, IL-1β, and FST, after 4th week of feeding trial which was increased ~2 to 3 times on 1dpi and 3 dpi. These results indicate that limonene rich (91.26%), HPO enriched diets enhance growth and immunity and enhance disease resistance of Oplegnathus fasciatus challenged against E. tarda.