Preliminary assessment of restaurant food waste as a feed ingredient for small juvenile rainbow trout (Oncorhynchus mykiss)

Growth of fed aquaculture is dependent on finding sustainable and inexpensive ingredients that would satisfy the nutritional requirements of fish. The present work assessed restaurant post-consumer food waste as an ingredient in feeds for small (ca 6.5 g) rainbow trout, Oncorhynchus mykiss. Food waste from Lebanese-food restaurants was used to prepare seven iso-nitrogenous feeds (ca 42.5% protein, 18% lipid) by replacing soybean meal (SBM), soy oil, and whole wheat in a control diet. Seven diets containing 0, 5, 10, 15, 20, 25, and 30% food waste were made. Fish were stocked in triplicate 52-L tanks (15 fish per tank) and offered the feeds at 4% body weight daily for 8 weeks. Growth, hematology, and proximate chemical composition of the fish were assessed. Results show that food waste can be incorporated as 25% of the diet without affecting growth of O. mykiss. The best growth (ca 317% from initial stocking weight) was observed in fish offered feed with 20% food waste. Feed treatment did not significantly affect hematology, but significantly affected body composition. Total fish body protein proportion was greater in the treatment offered 30% food waste feed than in the control. There seems to be a potential for using food waste as an ingredient in trout feed, and this could mitigate the environmental consequences of disposal of food waste.