Understanding the interaction between terrestrial animal fat sources and dietary emulsifier supplementation on muscle fatty acid profile and textural properties of European sea bass

The main goal of this work was to compare the dietary inclusion of poultry fat with mammal fat, and to understand the possible beneficial effects of an emulsifier in commercial-based diets for European sea bass (Dicentrarchus labrax) tested under an industrial scale, without control of environmental conditions. Effects on growth performance and muscle quality in terms of fatty acid (FA) profile, textural properties and colour, were evaluated. For this purpose, four isoproteic (45%) and isolipidic (21%) diets were formulated using the same protein sources. The lipid fraction of the diets varied, and comprised 55% fish oil and either 45% poultry fat or mammal fat, with or without an emulsifier. A 12 weeks' growth trial was carried out with commercial-sized juveniles (255.7 ± 15.2 g) in an open-through aquaculture system. All diets were equally well-accepted by the fish, with no differences in terms of feed efficiency and growth. The inclusion of the emulsifier led to increased whole body lipids and energy contents, regardless of the type of fat. Fish fed with the mammal fat diet had a higher muscle lipid content, but lower n-6 PUFA, without changes in the n-3 PUFA and in the n-3/n-6 PUFA ratio. The dietary inclusion of mammal fat, contrarily to poultry fat, resulted in increased amounts of EPA and DHA in the muscle which were within the recommended levels for human consumption to decrease the risk of cardiovascular diseases (> 0.25 g 100 g⁻¹). Fish fed mammal fat also demonstrated an increase of muscle instrumental lightness and hardness. These results indicate that terrestrial animal fats can be promising sources of lipids for aquafeeds, highlighting mammal fat as a viable by-product to include in European sea bass diets.