Application of taurine in aquaculture nutrition

Taurine, or 2-aminoethanesulfonic acid, is an end product of metabolism of sulphur-containing amino acids. Taurine is found in eggs, fish, meat, and milk, but not in vegetable proteins. It is present in high concentrations in heart, retina, skeletal muscle, brain, large intestines, plasma, blood cells and leucocytes. Therefore, this amino acid plays significant roles in many physiological functions, including membrane stabilization, antioxidation, detoxification, modulation of immune response, calcium transport, myocardial contractility, retina development, bile acid metabolism, osmotic regulation and endocrine functions. In the past, taurine has not been considered as an essential nutrient for fish. However, recent studies have indicated that taurine synthesis widely differs between fish species and demonstrated that it plays a key role in nutrition of fish and shellfish. Fish meals, which are the primary protein source in aquaculture feed industry, have become costly and of limited availability. In recent years, plant-based protein sources, have been receiving considerable attention as a partial or total fishmeal replacer in aquaculture feed industry. However, most ingredients of plant origin are limited in a number of nutrients, including taurine, which might be necessary for the optimal performance and metabolism of farmed aquatic animals, particularly for carnivorous fish. Plant protein sources are deficient in taurine or its precursors, namely cysteine and methionine. The inclusion of high levels of plant protein in fish feeds is cause deterioration in fish performance, possibly due to the inability, or low ability, of these fish to synthesize taurine. On the other hand some freshwater teleost fish are able to synthesize taurine from methionine and cysteine. In this review we describes the taurine sources, requirement levels in some farmed species, and highlights the biological activities of taurine.