Insight into bioavailability of various insect meals for European perch (Perca fluviatilis): A nutritional and stable isotopic evaluation

The present study evaluated nutritional composition, stable isotopic signature, apparent digestibility coefficient (ADCs), and relative contribution of seven insect meals, namely black soldier fly (Hermetia illucens) (BSF), common housefly (Musca domestica) (CHF), yellow mealworm (Tenebrio molitor) (YMW), lesser mealworm (Alphitobius diaperinus) (LMW), house cricket (Acheta domesticus) (HC), banded cricket (Gryllodes sigillatus) (BC) and field cricket (Gryllus assimilis) (FC), on European perch (Perca fluviatilis), a potential aquaculture species in Europe. Nutritional composition on a dry matter basis varied widely across insect species. YMW, HC, and BC appeared to contain high protein content (>70%), whereas lower content was found in defatted BSF, LMW, and CHF (ranging 55–59%), adult FC remained intermediate (66.83%). Lipid levels were highest in LMW and CHF (27.72% and 26.53%, respectively), medium in BSF, HC, BC and FC, and lowest in the highly defatted YMW (8.14%). Methionine and lysine were the first limiting amino acids in all insect meals. Heatmap visualization indicated considerable similarity in amino acid profile between fishmeal and YMW. Most insect meals contain a high amount of saturated, monosaturated fatty acids and a lack of n-3 fatty acids. Although macro-minerals were lower in insect meals than in fishmeal, the trace minerals of YMW, BSF, HC, and FC surpassed fishmeal, implying that insect meals are an excellent source of trace minerals. The digestibility of nutrients and energy differed significantly among insect meals. Dry matter ADC varied from 67.91% (YMW) to 85.02% (LMW), with LMW and CHF significantly higher than YMW. Protein ADC was lowest in YMW (69.03%) and greatest in LMW (91.94%) and CHF (93.53%). BSF and HC exerted absolute lipid digestibility (104.86 and 99.99%, respectively), followed by LMW (94.75%), whereas BC had the lowest lipid digestibility among insect meals. Energy digestibility favored BSF, CHF, FC, HC, and LMW, but not BC and YMW. Ash and phosphorus digestibility did not differ among insect meals. FC contributed significantly to perch muscle development (mean and interquartile range; 23.9, 10.6–33.8%), followed by CHF (19.8%, 8.8–29.7%), whereas BC imprints relatively low contribution (12.6%, 7.4–17.4%). The stable isotope and mixing models provide insight into the role of ingredients in the accretion of perch muscle as well as in nutritional complementarity among them in satisfying nutrient requirements, thus gr