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Abstract

Availability of nutritionally balanced commercial feeds is essential in producing healthy, high-quality aquatic animals. Protein is the most important component of aquaculture feeds. Fish require not only a minimum level of protein but also that the essential amino acids are balanced to meet the requirements of each single one. Histidine is an essential amino acid with several functions including protein synthesis, tissue formation and repair as well as maintenance of osmoregulation and myelin sheaths. It also regulates the immune system and acts as antioxidant in fish. Histidine deficiency depresses growth performance and feed utilization. If in excess, it causes disruption of the balance of dietary amino acids leading to toxicity or extensive necrosis in the epithelial cells. Furthermore, histidine serves as an important antioxidant and buffer in various organs of several fish species. In aquaculture, extensive research has been carried out to optimize the levels of histidine in the commercial diets for many fish species. Providing adequate levels of this amino acid is critically important for fish growth. Currently, available data suggest a wide variation in histidine requirements of different species ranging between 0.89-3.54% on protein basis.