NUTRITIONAL REQUIREMENTS OF TURBOT (Scophthalmus maximus): I. A PRELIMINARY STUDY OF PROTEIN AND LIPID UTILIZATION

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Abstract
Twelve groups of 10 g turbot were fed ad libitum for 42 days. Each group was given a diet containing 37.5, 48.3, 59.2 or 69.8% protein, and 10, 15 or 20% lipid. Food consumption was similar for all diets. Specific growth rate (SGR) increased and feed conversion (FC) decreased with increasing dietary protein content. The best SGR (2.5%) and the best FC (0.57) were obtained with the 69.8% protein‐10% lipid diet. Lipid had a negative effect on growth and food conversion except for low protein diets. Carcass protein and lipid content were not influenced by diet composition. Liver lipid content was nearly constant and showed no trend in relation to the diet composition for 15 and 20% dietary lipid. The fish fed the 10% lipid diet showed higher liver lipid content. Liver glycogen increased with decreasing dietary protein content. High dietary protein levels enhanced daily tissue protein deposition. With the exception of the 37.5% protein‐20% lipid diet, which showed the best protein efficiency ratio (PER=3.1%) and the best protein utilization coefficient (PUC=50%), all the other diets gave similar PER and PUC values, from 2.2 to 2.6% and from 36 to 43%, respectively.