DIETARY ESSENTIAL AMINO ACID REQUIREMENT OF DUSKY KOB Argyrosomus japonicus

Adejoke A. Adesola^a* Thomas A. Shipton^b and Clifford L.W. Jones^b

^aSchool for Resources and Environmental Studies, Dalhousie University, PO Box 15000 Halifax, NS, B3H 4R2, Canada.
^aDepartment of Ichthyology and Fisheries Science, Rhodes University, PO Box 94, Grahamstown 6140, South Africa
*Corresponding author, email: joke.adesola@dal.ca

Protein is the most expensive dietary component and is central to growth. An understanding of the dietary essential amino acid (EAA) requirements of a species is important for developing cost effective feeds. Based on lysine requirement it may be possible to estimate other EAAs by modelling with fish body EAAs composition, such estimation has been carried out in striped bass, colliroja, red sea bream, Japanese flounder and bluegill. Dusky kob is an economically important fish in South Africa and in other parts of the world. However, the information on the dietary essential amino acid requirements of this species is not available. Therefore, this study aimed to estimate the dietary essential amino acid requirement for dusky kob by using ideal protein concept.

Eighty seven juvenile dusky kob Argyrosomus japonicus with an average weight of 1.2±0.1 g were collected from a commercial fish farm, euthanized, placed in crushed iced and transported to the laboratory for amino acid analysis.

The mean whole body amino acid level of juvenile dusky kob ranged from 0.2% (cysteine) to 16.1% (glutamic acid). These data, together with a dietary lysine level of 7.3% protein were used to estimate the dietary requirements of the other essential amino acids. The dietary requirements of these amino acids ranged from 2.2% for histidine to 7.1% for leucine (Table 1).