Provided high product quality, ensilaging can be used to valorize fish filleting co-products into a silage suitable for food applications. However, a documented challenge for products from hemoglobin-rich fish raw materials is the high susceptibility to lipid oxidation, calling for stabilization by antioxidants. In a comparison among different rosemary-containing antioxidants and isoascorbic acid, we here found that the commercial mixture Duralox MANC-213 (MANC) provided the best protection against peroxide value and 2-thiobarbituric acid reactive substances (TBARS) development during ensilaging of herring filleting co-products (0–7\ua0days, 22\ua0\ub0C), and also during subsequent heat-treatment (30\ua0min, 85\ua0\ub0C). Increasing MANC concentration from 0.25 and 0.75 to 1.25% lowered TBARS values from 43.53 and 25.12 to 18.04 \ub5mole TBARS/Kg silage, respectively, after 7\ua0days of ensilaging. During storage at 4\ua0\ub0C/22\ua0\ub0C in presence of MANC, 1.25% provided the highest protection with 87–90% and 66–73% lower TBARS, at 4\ua0\ub0C and 22\ua0\ub0C, respectively, at 6\ua0months compared to the controls. At this time point, heat-treated silages had lower protein degree of hydrolysis and free amino acids values than the non-heat-treated one. Regardless of antioxidant addition, total volatile basic nitrogen (TVB-N) formation still increased during the storage, but, overall, TVB-N values in silages were below the acceptable limit of 30\ua0mg TVB-N/100\ua0g fish for human consumption. Together with lipid oxidation data, this suggests that herring silage produced in presence of antioxidants can be used both for high-quality feed and food applications
