Comparison of Different Dietary Fatty Acids Supplement on the Immune Response of Hybrid Grouper (Epinephelus fuscoguttatus × Epinephelus lanceolatus) Challenged with Vibrio vulnificus

SIMPLE SUMMARY: Groupers are one of Asia’s most valuable marine fish. The strong market demand has driven the expansion of grouper farming. However, with the intense farming practices, the farm rearing system was exposed, thus increasing the risk of infectious diseases. The present study was conducted to compare the use of different fatty acid immunostimulants on the survival, growth, and immune response of hybrid grouper infected with Vibrio vulnificus. Our results showed that the oleic acid formulated diet gives the highest fish survival rate and growth rate compared to the other fatty acid formulated diets and control diet after six weeks of feeding trial and one week of the bacterial challenge. Moreover, fish supplemented with an oleic acid diet showed significantly increased immune responses after being infected with V. vulnificus. ABSTRACT: Aquaculture has been expanding in Malaysia due to the increased demand for fish products. In addition, aquaculture faces challenges in maintaining feed suitability in support of the global growth of fish production. Therefore, improvements in diet formulation are necessary to achieve the optimal requirements and attain a desirable growth efficiency and health performance in fish. Seven weeks of study were conducted to compare the equal amounts of different fatty acids (2%) (oleic acid, stearic acid, palmitic acid, and behenic acid) on the survival, the growth, and the immune response of hybrid grouper (Epinephelus fuscoguttatus × Epinephelus lanceolatus) against V. vulnificus. After six weeks of the feeding trial, fish were challenged with V. vulnificus for 30 min before continuing on the same feeding regime for the next seven days (post-bacterial challenge). Fish supplemented with dietary oleic acid showed significantly (p < 0.05) enhanced immune responses, i.e., lysozyme, respiratory burst, and phagocytic activities compared to the control diet group for both pre-and post-bacterial challenges. Following the Vibrio challenge, no significant effects of supplemented fatty acid diets on survival rate were observed, although dietary oleic acid demonstrated the highest 63.3% survival rate compared to only 43.3% of the control diet group. In addition, there were no significant effects (p > 0.05) on specific growth rate (SGR), white blood cell (WBC), and red blood cell (RBC) counts among all experimental diets. The results from this study suggest that among the tested dietary fatty acids, the oleic acid diet showed promising results in the form of elevated immune responses and increased disease resistance of the hybrid grouper fingerlings challenged with V. vulnificus.