Nutritional deficiency

Interest in fish nutrition has increased markedly over the past two decades, largely due to the global increase in aquaculture production. Nutritional status is considered one of the important factors that determine the ability of fish to resist diseases. Outbreaks of fish diseases commonly occur when fish are stressed due to a variety of factors including poor nutrition. The need for proper diets to improve health and prevent diseases of farmed aquatic animals is widely recognized. Nutritional and physical characteristics of diets can modulate susceptibility of fish to infectious diseases. In the most severe cases, diets that are inadequate with respect to essential nutrients (protein, amino acid, essential fatty acids, vitamins and minerals) lead to gross malnutrition and high disease susceptibility. In general, gross malnutrition is no longer a problem, however, we are now faced with the more challenging task of determining the more subtle effects that micronutrients, and their interactions with other dietary components have on the immune system of fish. Several reviews have dealt with the subject of nutrition and immune response in fish (Blazer, 1992; Lall and Olivier, 1993; Waagbo, 1997). In the past two decades significant advances have been made in establishing the quantitative requirements of more than 40 essential nutrients for optimum growth and better feed utilization, as well as to prevent deficiency diseases of single or multiple nutrients (NRC, 1993).

Mineral elements have a great diversity of uses within the animal body. The following mineral elements are recognized as essential for body functions in fish: calcium, phosphorus, sodium, molybdenum, chlorine, magnesium, iron, selenium, iodine, manganese, copper, cobalt and zinc. To these many are added like enzymes, probiotics etc. which have very important role such as better digestion, growth and overall performance of fish in aquaculture.

Ascorbic acid is an essential vitamin of fish. Deficiencies of this vitamin lead to poor wound healing, ulceration of the skin on fins, hemorrhage, and skeletal deformity. This vitamin is very temperature sensitive and oxidizes readily in stored feed.

Factors influencing nutritional status, health and immune function of fish