Fatty and defatted herring scrap fed to mink (Mustela vison) in the reproduction and nursing periods

The use of fatty herring scrap and defatted herring scrap products for female mink in the reproduction and nursing periods was investigated in two experiments. In exp. 1, diets with 27% fatty herring scrap with 60 vs. 120 mg vitamin E kg−1 feed, and 10 vs. 19% defatted herring scrap ensiled with formic and acetic acids were compared with a control diet without fatty herring scrap or defatted herring scrap silage. Each dietary group consisted of 137 females. In exp. 2, diets with 20% fatty herring scrap with 63 vs. 78% of the dietary fat originating from fish, and diets containing 20 vs. 29% defatted herring scrap were compared with a control diet without fatty herring scrap or defatted herring scrap. Each dietary group consisted of 90 females. The results showed that fatty herring scrap, defatted herring scrap and defatted herring scrap silage can be used at these levels during the winter and reproduction periods until parturition, without any negative effects on the number of kits per female at parturition and weaning. However, use of defatted herring scrap silage in the nursing period resulted in lower kit weights at weaning. There were also some indications that high amounts of dietary fat from herring led to reduced kit weights at weaning; therefore, reducing the fat content in herring seemed to be appropriate in order to reduce the content of fish fat in the diet in the nursing period. The recommended addition of 60 mg vitamin E kg−1 wet feed, with an energy density of 5–6 MJ kg−1 during winter, reproduction and nursing periods, was sufficient according to the plasma content of α -tocopherol. Furthermore, there were no negative effects in the nursing period of feeding fatty or defatted herring scrap during the preceding rearing season of the females. Key words: Mink, marine lipid, polyunsaturated fatty acid, haematology, α -tocopherol, acid silage