Nutrition and disease resistance in fish

Abstract

Disease resistance in fish encompasses a variety of mechanisms including maintenance of epithelial barriers and the mucus coat; nonspecific cellular factors such as phagocytosis by macrophages and neutrophils; nonspecific humoral factors such as lysozyme, complement, and transferrin; and specific humoral and cellular immunity. Numerous nutritional factors can significantly affect incidence and severity of a variety of infectious diseases. Individual micronutrients known to affect disease resistance include vitamins C, B₆, E, and A and the minerals iron and fluoride. Macronutrient (protein, lipid, and carbohydrate) levels have not been critically evaluated. There are indications that certain fatty acids may be important factors in disease resistance. The potential for dietary enhancement of disease resistance in fish culture certainly exists. Before this can be achieved, more information is required on pathogenesis and specific resistance mechanisms involved in individual diseases, the specific effects of various nutrients, and how these effects are modulated by other dietary components and environmental factors.