Fermented soybean meal can partially replace fishmeal and improve the intestinal condition of goldfish juveniles reared in a biofloc system

This study evaluated the effects of different dietary inclusion levels of fermented soybean meal (FSM) as replacement for fish meal and their effects on the productive performance and intestinal condition of goldfish (Carassius auratus) produced in biofloc (BFT) system. Five isoproteic (39.5% crude protein) and isoenergetic diets (4250 kcal kg(-1) of crude energy) were formulated with FSM inclusion levels of 0%, 7%, 14%, 21% and 28% (0, 11, 22, 32 and 43 fish meal replacement). A total of 400 goldfish (0.25 +/- 0.02 g) were weighed and distributed in 20 glass aquariums (15 L). Fish were fed twice daily for 56 days. The diet with FSM inclusion level of 28% reduced the weight gain and the specific growth rate and increased the feed conversion of the goldfish. Diets with FSM inclusion levels of 21% and 28% increased the alpha-amylase activity in the fish intestine. The diet with FSM inclusion level of 21% increased total height of the intestinal villi of the goldfish. In conclusion, the inclusion of up to 21% of FSM can replace fishmeal without affecting the growth of goldfish juveniles reared in BFT system. Fish fed 21% of FSM showed evidence of improvement in the intestinal health.