Fermented food waste for culturing jade perch and Nile tilapia: Growth performance and health risk assessment based on metal/loids

Food waste is a low-cost and nutritious source of feed which could be beneficial to the fishery industry. The objective of this study was to use fermented food wastes as major sources of protein to replace the fish meal used in fish feeds for culturing jade perch (Scorinm barcoo) and Nile tilapia (Oreochromis niloticus). Two experiments (a laboratory and a field trial) were conducted to test the suitability of the fish feeds for the two fish species. In the laboratory trial, six out of seven formulations (six food waste-based formulations and one commercial diet as control) were tested on jade perch whereas four out of the seven formulations were tested on Nile tilapia to study the effects of the diets on the growth performance and serum immunological parameters of fish. The formulations (Diet F and Diet A) with the best growth performance (feed conversion ratio (FCR) of jade perch (1.98) and Nile tilapia (1.28)) while having the lowest amount of fish meal (55/a) were selected for field scale feeding trial. In addition, the percentage of fermented food waste ingredient in fish feed (Diet A and Diet F) was about 50% without causing significant effects on the immunity (P < 0.05) of the two fish species when compared with control diet. In the field scale feeding trial, FCR values of jade perch and Nile tilapia fed with Diet F and A were 1.06 and 1.16, respectively, which were similar to the control diet (P > 0.05). Metal/loids concentrations in fish tissue showed that both fish species fed with food waste-based pellets (Nile tilapia) Diet A: As (0.028 mg/kg), Cd (0.011 mg/kg), Cr (0.163 mg/kg), Cu (0.851 mg/kg), Hg (0.141 mg/kg), Pb (0.081 mg/kg) and Zn (30.8 mg/kg)) and jade perch Diet F: As (0.709 mg/kg), Cd (0.026 mg/kg), Cr (0.300 mg/kg), Cu (2.49 mg/kg), Hg (0.318 mg/ kg), Pb (1.745 mg/kg) and Zn (40.9 mg/kg) were all below the maximum permissible levels of the local standard (As (AS(2)O(3)) = 6 mg/kg; Cd = 2 mg/kg; Cr = 1 mg/kg; Pb = 6 mg/kg; Hg = 0.5 mg/kg), while no permissible levels of Cu and Pb are stipulated by the standard. The results of the human health risk assessment indicated that the fish cultured with food waste-based diets were generally safe for human consumption (Hazard Index values: 0.075-0.054; cancer risk range: 2.14-8.15 x 10(-6)). The present study revealed that fermented food waste could serve as protein substitute in fish feed for the culture of quality jade perch and Nile tilapia for human consumption.