INCLUSION OF OXIDIZED FISH-OIL IN MINK DIETS .1. THE INFLUENCE ON NUTRIENT DIGESTIBILITY AND FATTY-ACID ACCUMULATION IN TISSUES

In a feeding experiment with 18 male, adult, pastel mink over a period of 15 weeks, the influence of high amounts (55 % of metabolizable ene rgy) of fresh and oxidized fish oil (200 and 400 meg. O-2/kg oil) on p erformance and fatty-acid accumulation in liver and inguinal fat was e xamined. The apparent digestibily of macronutrients, fatty acids and a lpha-tocopherol was determined during the eighth week of the experimen t. The quality of the experimental oils was followed during oxidation and storage (13 weeks, -80 degrees C exclusion of light and oxygen). D uring storage, the peroxide values of the respective oils were kept re latively stable but a considerable loss of n-3 fatty acids was recorde d especially in the heavily oxidized oil (400 meq. O-2/kg oil). The ap parent digestibility of crude fat decreased from 95 % (fresh oil) to 9 1 % (200 meg. O-2/kg oil) and 74 % (400 meg. O-2/kg oil). The apparent digestibility of total fatty acids decreased in parallel. The apparen t digestibility of alpha-tocopherol was in the range of 60 % and was n ot influenced by the dietary fat quality. Feed intake, growth and perf ormance in the mink were negatively affected, in particular by the hea vily rancid fish oil. The fatty acid composition of the liver and ingu inal fat clearly reflected the marine origin of the dietary fat source . The accumulation of long-chain fatty acids (C20, C22) was extremely high in both liver (28-31 % of total fatty acids) and inguinal fat (38 -42 %).