Fish Nutrition and Feed Technology (2+1)

Unit 9 - Nutritional requirements of cultivable fish and shell fish

9.2.1.Protein and amino acids

The gross protein requirement decreases with increase in age and size of fish. However, generally 25-30% protein is optimum for practical diets for herbivorous and omnivorous fishes for pond feedings.

The gross protein requirement for carp fry and fingerlings vary from 36-45%. The protein requirement is higher in catla fry (45-47%) than fingerlings (40%). The protein requirement in silver carp fry ranges from 37-42% and for common carp it is 31%.

The information on protein requirement is of limited value unless amino acids requirement of fish is understood. The fish does not have true protein requirement but need a well-balanced mixture of essential and non-essential amino acids. Gross protein requirement of a fish is the requirement of essential amino acids and some non-essential amino acids to maintain metabolic activities. With hydrolysis of protein, about 20 different amino acids are released, out of which 10 are essential – arginine, histidine, isoleucine, leucine, lysine, methionine+cystine, phnylalanine+tyrosine, threonine, tryptophan and valine, which are not biosynthesized and hence required by fish.

Essential amino acid requirements (% dietary protein) of some fish and prawn species

There exists a high correlation between dietary amino acid requirements and body composition of amino acids and the data thus obtained suggest that EAA requirement of Indian major carps like catla, rohu and mrigal would not vary widely.