Ability of European seabass (Dicentrarchus labrax) to digest rendered animal fats from fish, poultry and mammals

This study evaluates the in vivo apparent digestibility coefficients (ADC) of rendered animal by-product fats in European seabass (Dicentrarchus labrax) juveniles. Diets contained fish oil (FOd), poultry fat (PFd) or mammal fat (MFd), from rendering animal by-products, at 140 g/kg. Macronutrient and fatty acids ADCs were evaluated in quadruplicate tanks with fifteen 100 g fish. While total lipids ADCs (88%–90%) were unaffected, individual fatty acids ADC varied significantly among diets. Monounsaturated fatty acids ADCs were similar (94%–95%), saturated fatty acids ADCs were lowest in MFd (85% vs. 91% in PFd and FOd), and polyunsaturated fatty acids (PUFA) ADCs were lowest in PFd (96 vs. 97%–98%). Total n-3 PUFA were better digested in FOd than in the other diets (98 vs. 96%–97%), while MFd had the highest total n-6 PUFA ADC. FOd showed significantly higher EPA (20:5n-3) and DHA (22:6n-3) ADCs compared to the other test diets. The obtained results suggest that rendered animal fats can be considered feasible alternatives to fish oil in seabass. Nevertheless, that lack of EPA and DHA in land animal fats, combined with the reduced digestibility of these fatty acids, may compromise its dietary inclusion at high levels.