Evaluation of rapeseed protein concentration as protein source of diet for red sea bream

Abstract

Red sea bream Pagrus major having a mean body weight of 18.5 g were reared on diets containing 0, 10, 20, and 30% of rapeseed protein concentrate (RFC) for 52 days. Glucosinolates, sinapine, and phytic acid contents of RFC were respectively 0.58 μmol/g, 0.2%, and 4.4%. Final mean body weights of fish fed the 20 and 30% RFC diets were lower than fish fed the 0 and 10% RFC diets. No significant differences among the dietary treatments were found in daily feed intake, feed efficiency, protein efficiency ratio, hematology, and relative weight of the hepatopancreas, stomach and intestine to body weight. Crude fat content of the whole body fell, but that of the hepatopancreas increased with an increase in diet RFC levels. Hematological character and plasma total protein, albumin, cholesterol, Mg and Zn concentrations did not show any differences among the dietary treatments. However, plasma P concentrations of fish fed the 0 and 10% RFC diets were higher than fish fed the 30% RFC diet. Moreover, apparent protein and sugar digestibilities fell slightly with an increase in dietary RFC contents. These results suggest that a practically substituitve limit with RFC for dietary brown fish meal is about 10% in red sea bream.