Protein to energy ratios in African catfish fed purified diets: is Clarias gariepinus (Burchell) an ordinary carnivore?

Abstract

Six diets made from purified and semi-purified materials (casein, gelatin, gluten, zein, dextrin, a-cellulose) were tested over an 80-day period in adult (150 ± 47.40 g) African catfish, Clarias gariepinus (Burchell). Six protein to lipid ratios were tested ranging from 12.85 mg protein kJ-1 to 20.51 mg protein kJ-1. Performance indices (PWG, SGR, FCR) compare favorably with those previously observed for C. gariepinus and other clariid species. The best performing diets were those with a total gross energy range of 22 to 24 kJ g-1, a P/E ratio of 19.5-20.5 mg protein kJ-1, a crude protein level of 46%, a crude lipid level of 10-17%, and a carbohydrate level of 26-32%. The carbohydrate levels (26-32%) of the best performing diets during these experiments were much higher than those of previous researchers (16-18%) for the same species and still higher than those (15-25%) employed for other carnivores (salmonids, sea bass, sea bream). Therefore, African catfish possibly exhibits more efficient dietary carbohydrate utilization. An increase in carcass lipid as a result of increased dietary non-protein energy was also recorded.

CORRESPONDING AUTHOR:

Panagiotis A. Pantazis, University of Thessaly, Department of Agriculture, Animal Production and Aquatic Environment, Fytokou Street, Nea Ionia Magnisias, 384 46 Volos, Greece, Tel./Fax: (30) 421-93259, (30) 24210 93157;
e-mail: papantaz@uth.gr