Abstract

Four commercial diets containing different levels of crude protein and crude lipid (44/25, 43/21, 46/20 and 47/20%) were assayed in duplicated groups in juvenile meagre (Argyrosomus regius) (initial individual weights were 94 g) in an experiment lasting 173 days. The essential amino acid contents (expressed in g/kg of diet basis) in diets 46/20 and 47/20 were higher than in diets 44/25 and 43/21. The HUFAs represented 184 and 207 g/kg in diets 46/20 and 47/20, respectively and 98 and 116 g/kg in diets 44/25 and 43/21, respectively. The fish fed diet 47/20 obtained the best growth and efficiency results, reaching a final individual weight of 393 g, followed by the meagre fed with diet 46/20. Meagre from the 47/20 group retained more of the ingested protein and energy than those  fed diets 46/20.  Fish fed 44/25 and 43/21 obtained the significantly lowest protein and energy efficiency. The retention of individual amino acids (AAs) in fish fed diets generally decreased in order of diets 46/20, 43/21 and 44/25. The IAA retention of meagre fed diet 47/20 was around 24.8% in phenylalanine and 39.7% in lysine. The results of the current experiment show that the fish fed commercial diet 47/20 obtained the best results in meagre growth, followed by fish fed diet 46/20. Diets 43/21 and 44/25 presented the worst growth and feed efficiency results.

Key words: Meagre, protein level, lipid level, extruded diets.