Total Replacement of Fish Meal with Other Protein Sources in the Diet of Japanese Flounder, Paralichthys olivaceus

Abstract

Feeding experiments were conducted to examine the effects of dietary protein sources on the growth of Japanese flounder, Paralichthys olivaceus. White fish meal (WFM), cuttlefish meal (CFM), soybean meal (SBM), feather meal (FM), brewers yeast (BY), and egg white albumin (EWA) were used as single protein source, and the crude protein content of the diet was in the range of 41 to 51 %. The rearing period was 8 weeks for the juveniles and 5 weeks for the young fish at 20 °C. The effects of the protein sources on nitrogenous excretion were also examined.
Both in juvenile and young flounder, the survival rate of the fish fed on BY diet was extremely low. In juveniles, the weight gain, feed conversion efficiency and protein efficiency ratio were high in fish fed on WFM and CFM diets, and low in those fed on FM and EWA diets. These parameters were also lower in young fish fed on FM and EWA diets than those in the WFM, CFM and SBM diets.
Proportions of excreted to consumed nitrogen were extremely high in the flounder fed on BY and EWA diets. In the BY diet, the amount of nitrogen excreted as ammonia and urea accounted for more than 50 % of the consumed nitrogen. On the other hand, about 50 % of the consumed nitrogen was excreted as faeces in the EWA diet. Nitrogenous excretions of the flounder fed on SBM diet were similar to those fed on WFM and CFM diets.