Insects are emerging as a sustainable alternative to fishmeal and
fish oil in aquafeeds. This study assessed the effect of graded incorporation levels of defatted yellow mealworm (Tenebrio molitor)
protein meal on juvenile rainbow trout (Oncorhynchus mykiss) growth performance, body composition, and apparent nutrient digestibility. The trial comprised five dietary treatments: control diet with 25% fishmeal, and four experimental diets with yellow mealworm
protein meal at 5%, 7.5%, 15%, or 25%, which corresponded to a fishmeal replacement of 20%, 30%, 60%, or 100%, respectively. After 90 days, the graded incorporation of
insect protein meal led to a significant stepwise increase in final
body weight, and a significant improvement of specific growth rate, feed conversion ratio, and
protein efficiency ratio compared to the control treatment. Regardless of the incorporation level, the
insect protein meal had no effects on fish whole-body composition and apparent digestibility coefficients of dry matter,
protein, fat,
phosphorus, and energy.
Protein,
phosphorus, and energy retention significantly increased in fish fed the diets with an
insect protein meal. In conclusion, the yellow mealworm
protein meal could effectively replace 100% of fishmeal in the diet of juvenile rainbow trout with positive effects on its overall zootechnical performance.