Growth of dentex fingerlings ( Dentex dentex) fed diets containing different levels of protein and lipid

Abstract

Dentex fingerlings weighing 2.5 g initial live weight were fed 12 extruded diets containing four crude protein levels (40%, 45%, 50% and 55%) and three crude lipid levels (12%, 17% and 22%) according to a factorial design, for 6 weeks. Survival was high (84–92%) and specific growth rate (SGR) values were 3.4%, 3.9%, 4.3% and 4.1% day −1 and food conversion ratio (FCR) were 2.2, 2.1, 1.5 and 1.9 for fish fed the diets containing 40%, 45%, 50% and 55% crude protein, respectively. With respect to lipid levels, SGR values were 4.2%, 4.0% and 3.6% day −1 and FCR were 1.7, 1.8 and 2.3 for 12%, 17% and 22% crude lipid, respectively. The effects of protein and lipid levels were significant; final live weight, SGR, FCR and PER values were best for fish fed 50% crude protein and poorest for those fed 22% lipid diets. The best growth performance was observed in fish fed diets containing 50/12 and 50/17 protein/lipid ratios. The results indicate that optimum growth and nutrient utilisation of dentex fingerlings can be obtained when they are fed a diet containing around 50% crude protein with a lipid level ranging from 12% to 17%, and having a crude protein/gross energy ratio from 22 to 25 g MJ −1.