Dietary Effects of Omega-3 Polyunsaturated Fatty Acids on Body Fat Composition and Health Status of Farm-raised Blue and Silver Foxes

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Abstract
Farm-raised blue and silver foxes were fed diets based on slaughterhouse offal (SH) and fish mixture supplemented with fish oil (FM) from weaning to pelting in order to clarify the effects of accumulation of omega-3 fatty acids in the tissues and organs. Some blue foxes were also fed an antioxidant (Rexoquin®, 200–1000 ppm) supplemented diet. The dietary background of the animals significantly influenced the fatty acid composition of all body fat depots in both fox species. The animals of the FM group had considerably more eicosapentaenoic (EPA), docosahexaenoic (DHA) and cetoleic acids in their tissues than the animals of the SH group. In silver fox livers, the amount of DHA was even higher than in blue foxes. Fat accumulation pattern of the blue and silver fox livers also differed considerably between the diets. In the SH diets fat accumulated in the liver in large droplets, while in the FM diets it was present in small droplets. Furthermore, degenerative changes were more numerous and severe in the FM dietary group. The antioxidant supplementation of the blue fox diets employed appeared to be toxic to the animals. It increased liver fat content, which was also seen as fatty degeneration of the liver. The increase in the levels of the serum transaminases ALAT and ASAT was clearly connected with the disturbances in liver functions and degenerative changes. Also an increase in serum cholesterol was observed in animals with cholestasis. Liver vitamin A and selenium levels were higher in the FM diets in silver foxes. In blue foxes, the antioxidant supplementation employed had no influence on the vitamin status of the animals.