Dietary protein requirement of sharpsnout sea bream (Diplodus puntazzo, Cetti 1777) juveniles

Abstract

A trial was undertaken to estimate the protein requirement of sharpsnout sea bream (Diplodus puntazzo) and the protein sparing of dietary lipids. Ten diets were formulated to contain 5 protein levels (ranging from 15 to 55%) and two lipid levels (12 and 18%). Each diet was assigned to duplicate groups of 15 fish with a mean individual body weight of 49.3g. A quadratic model was used to adjust weight gain and N retention (gkgABW−1day−1) to dietary protein levels. Based on that model, optimum dietary protein requirement was estimated to be 42.9% for maximum weight gain and 43.8% for maximum N retention, corresponding to a protein intake of 7.68gkgABW−1day−1. Protein requirement for maintenance was estimated to be 0.71gkgABW−1day−1. Dietary lipid level improved protein utilization efficiency but did not affect protein requirement. Whole-body protein content increased with dietary lipids and protein content, but no other relevant differences in body composition were noticed. Hepatosomatic index increased with dietary starch and lipid levels and was directly correlated to liver glycogen content. Diet composition affected plasma glucose clearance and cholesterolaemia but not plasma protein and triglyceride levels.