The Effects of Varying Dietary Protein Level on the Growth, Feed Efficiency, Protein Utilization and Body Composition of Gilthead Sea Bream Fry

Abstract

The effects of varying dietary protein level on several nutritional parameters of Sparus aurata fry were studied. Seven approximately isoenergetic diets were formulated with protein levels ranging from 35% to 65%, in increments of 5%. Highest specific growth rates were obtained in fish fed 55% protein at a fixed dietary feeding rate of 6% body weight per day, being significantly different from the other fish groups. Feed efficiency was significantly higher with diets containing the highest protein levels, when compared with dietary levels below 45%. Protein efficiency ratio values showed a trend towards an increase up to a maximum with 55% dietary protein, whereas carcass composition was only slightly affected. The minimum dietary protein level producing maximum growth of S. aurata fry was found to be 55%.