Dietary threonine requirement of Indian major carp, Cirrhinus mrigala (Hamilton), juveniles

A growth study was conducted to determine the dietary threonine requirement of juveniles of the Indian major carp (Cirrhinus mrigala) known as "mrigal". Diets containing casein and gelatin as sources of intact proteins were supplemented with crystalline amino acids to obtain a crude protein content of 40%. Six diets with different levels of threonine (1.0, 1.3, 1.5, 1.7, 1.9 and 2.1%) were fed to triplicate groups of mrigal juveniles twice a day for 56 days. The dietary threonine requirement, estimated by break-point analysis, was 1.66% of the dry diet (4.15% of the dietary protein). The highest growth and specific growth rate were recorded in fish fed the diet containing 1.7% threonine.