Commercial-Scale Evaluation of Finishing Diet Containing Poultry By-Product and Insect Meals for Sparus aurata: From Fish Welfare to Consumer Acceptance

Sustainable expansion of global aquaculture relies on innovative alternative diets that reduce dependence on marine-derived ingredients. Poultry by-product meal (PBM) and insect meal have emerged as promising protein sources, yet their combined use under commercial farming conditions remains poorly explored. This study evaluated a plant-based finishing diet low in marine proteins and supplemented with 10% Hermetia illucens larvae meal (HIM) and 30% PBM (H10P30) and compared it with a conventional commercial diet (COM) in gilthead sea bream (Sparus aurata) reared on a land-based farm for 65 days. Health and welfare indicators, product safety, fillet quality, fatty acid profile, oxidative status, and consumer acceptance were assessed. Fish fed the H10P30 diet showed a significantly higher body weight and specific growth rate and a lowered feed conversion ratio than COM-fed fish. No external or internal lesions or liver histopathological alterations related to the H10P30 diet were observed. While the diet influenced the fatty acid profile of raw fillets, differences disappeared after cooking, except for a higher C22:6n-3 content in cooked H10P30 fillets. Sensory analysis penalised COM fillets due to the perceived hard texture and low juiciness. In summary, incorporating both PBM and HIM into a plant-based finishing diet serves as a viable feeding strategy for gilthead sea bream, contributing to improved feed sustainability.