Raw Garlic (Allium sativum) Improves Nonspecific Immune Responses and Resistance Against Vibrio Alginolyticus Infection in Grouper (Epinephelus coioides)

Garlic contains various nutrients and healthful ingredients. The content of garlic products is closely related to their processing methods, and each compound has specific biological effects. Allicin, a heat labile compound, is considered the most important factor in garlic. Garlic powder is commonly prepared by subjecting raw garlic to thermal processing before being grounded into powder,and it is of interest to compare the biological activity of garlic powder with raw garlic in fish. This study investigated immune effects of raw garlic and garlic powder on groupers (Epinephelus coioides). Although raw garlic and garlic powder did not promote growth performance of groupers, they increased groupers' survival after fish were challenged with Vibrio alginolyticus, especially for fish receiving 80 g raw garlic/kg diet. The results indicated that phagocytosis, superoxide anion, and superoxide dismutase activity were significantly enhanced in groupers fed with diets containing raw garlic, and to a lesser extent in fish received garlic powder. No significant differences were found between different treatments in terms of serum albumin concentration or albumin/globulin ratio. Serum globulin concentration was temporarily enhanced in the groupers fed with 10 g raw garlic/kg diet or 10 g garlic powder/kg diet. These data suggest that diets with raw garlic and garlic powder could enhance nonspecific immune response of grouper and improve its resistance against V. alginolyticus and that immune effect of raw garlic is superior to that of garlic powder.