Quantitative l-lysine requirement of juvenile black sea bream (<i>Sparus macrocephalus</i>)

Abstract

An 8-week feeding experiment was conducted to determine the quantitative l-lysine requirement of juvenile black sea bream Sparus macrocephalus (initial mean weight: 9.13 ± 0.09 g, SD) in eighteen 300-L indoors flow-through circular fibreglass tanks provided with sand-filtered aerated seawater. The experimental diets contained six levels of l-lysine ranging from 20.8 to 40.5 g kg−1 dry diet at about 4 g kg−1 increments. All the experiment diets were formulated to be isoenergetic and isonitrogenous. Each diet was assigned to triplicate groups of 20 fish in a completely randomized design. Weight gain and specific growth rate (SGR) increased with increasing levels of dietary lysine up to 32.5 g kg−1 (P   0.05). All groups showed high survival (above 90%) and no significant differences were observed. The whole body crude protein and crude lipid contents were significantly affected (P   0.05), however, haemoglobin level was significantly influenced by different diets (P < 0.05). Analysis of dose (lysine level)-response (SGR) with second order polynomial regression suggested the dietary lysine requirement of juvenile black sea bream to be 33.2 g kg−1 dry diet or 86.4 g lysine kg−1 protein.