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. Introduction Threonine is an indispensable amino acid for growth of young fish (Wilson, 1989) and terrestrial animals (Visek, 1984). The required amount of threonine has been investigated in common carp (Nose, 1979), Japanese eel (Arai et al., 1972), channel catfish (Wilson et al., 1978), Nile tilapia (Santiago and Lovell, 1988), milkfish (Borlongan, 1991, catla (Ravi and Devaraj, 1991) and rohu (Murthy and Varghese, 1996). Cirrhinus mrigala, popularly known as “mrigal”, is one of the most widely cultured of the Indian major carps. The economic success of fish culture depends on the cost of feeds, particularly the cost of protein materials incorporated into the feed. Although gross protein requirements of mrigal have been established (Mohanty et al., 1990), no information is available on the threonine requirement of this species. Hence, the present study * Corresponding author.