Optimal feeding rate and feeding frequency during the grow-out phase (95-350 g) of tambaqui (Colossoma macropomum) reared in earthen ponds

Abstract Two feeding rates, 3% and 4% body weight per day (3%BW and 4%BW), and two feeding frequencies, twice and three times a day, were assessed during 84 days at the initial grow-out phase of tambaqui in earthen ponds. In a completely randomized 2x2 factorial experimental design in quadruplicates, 4,800 juvenile tambaqui (94.5 ± 6.4 g) were assigned to sixteen 300-m 2 earthen ponds. No mortalities or difference in growth between treatments were observed during the trial. Total feed intake and feed conversion ratio were low in the fish fed at 3%BW. Fat deposition in the fish carcass and concentration of glycogen and lipid vacuoles in the hepatocytes were also low in fish fed at 3%BW. Plasma cholesterol and triglycerides were higher in the fish fed three times a day at 4%BW. Increased concentration of malonaldehyde was observed in the carcass of fish fed three times a day at 4%BW at the end of the storage period. Fish fed twice a day presented higher total feed intake per meal than fish fed three times a day, demonstrating that tambaqui was able to regulate the feed intake to benefit from a low feeding frequency. No difference was observed in pond phytoplankton and zooplankton concentration or sediment chemistry. Fish fed at 3%BW presented higher stomach content weight, demonstrating the contribution of the natural food as a complementary nutrition to tambaqui. Based on the results, tambaqui of 95 to 350 g reared in earthen ponds may be fed twice a day at 3%BW.