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Oxidative metabolism of gut and innate immune status in skin and blood of tench (Tinca tinca) fed with different insect meals (Hermetia illucens and Tenebrio molitor)

Abstract:

Searching alternative protein sources in fish feeds is essential for aquaculture sustainability, and insect-based meals arise as a promising option. The objective of this study is to assess the possible impact that the inclusion of insect meal on the tench (Tinca tinca) diet would have on the innate immune system in mucus and blood, as well as on the oxidative metabolism in the digestive tract. Tench were randomly distributed into five experimental groups (3 tanks per group), each of which was fed to satiety with one of the following isoproteic and isolipidic experimental diets: a control fishmeal-based diet, and four diets that included Tenebrio molitor or Hermetia illucens meal replacing 15 or 30% of fishmeal (T15, T30, H15, and H30, respectively). None of the experimental diets had a negative impact on growth or diet utilization. The meal of both insects promotes a high antioxidant capacity in the digestive tract of tench, with a decrease in lipid peroxidation with respect to the fishmeal-based diet, except in H15 group that showed values similar to controls. Little influence of insect meal on the parameters that evaluate the innate immune response of tench was observed, although an infectious challenge may be needed to highlight these effects. Although none of the insect-based diets had a negative impact on growth of tench, T. molitor seems to be a better alternative than H. illucens for tench feeding. The environmental benefits of using insect meal in tench feed would be in line with the current economic interests of the aquaculture industry, so insects represent a valid and healthy substitute of fishmeal and plant meal for fish feeding.