Abstract
To promote sustainable aquaculture, plant-based ingredients are increasingly being used to replace fish meal (FM) and fish oil (FO) in diets, affecting critical fatty acid (FA) profiles in broodstock diets. These profiles are essential for reproduction and offspring survival. The absence of traditional fish-derived nutrients results in an altered FA composition, particularly a reduction in omega-3 long-chain polyunsaturated fatty acids (LC-PUFAs). This change is detrimental to trout reproduction over the long term. Current research gaps, especially regarding FA profiles and related metabolites, limit our understanding of the reproductive consequences of omega-3 deficient plant-based diets. To fill this knowledge gap, a two-year trial was conducted to compare the reproductive effects (spawning performances, egg quality, embryo development) of two diets on rainbow trout females: a plant-based diet containing linseed (10.8 %), palm (5 %), and sunflower oils (2.7 %), and a commercial diet with high FM (27 %) and FO (12.1 %) content. Both diets were similar in terms of protein (44 %), lipids (23.4 %), and energy (25 kJ/g). The study spanned from initial feeding to first reproduction, and fatty acid profiles and metabolites (selected enzymatic and non enzyamatic metabolites from FA) were examined in the broodstock diet, female muscle tissue, eggs, and fry. Trout fed a plant-based diet showed reduced reproductive traits such as lower weight and fecundity, but egg and embryo quality remained high. Survival and hatching rates were similar to those on commercial diets. The study revealed for the first time the critical role of maternal diet in the generation of lipid metabolites in the offspring, particularly DHA (F4-neuroprostane, maresin, 14-HDoHE) and AA (F2-isoprostane, prostaglandin E and F2, 8–12- 15-HETEs) oxylipins, highlightingthe complex dietary influences on fish reproduction. This work underlines that a plant-based diet significantly affects the the reproductive performance of broodstock trout by altering fatty acid profiles and metabolite levels and highlights the delicate balance between dietary components, oxylipins, and reproductive functions in fish, suggesting the need for more comprehensive studies of their interrelated effects.