Increased reproductive success in the white American mink (Neovison vison) with chronic dietary β-sitosterol supplement

β-Sitosterol is a weakly estrogenic phytosterol used in functional foods to lower elevated serum cholesterol concentrations. It has been reported to cause reproductive disturbances in fish and lower the sperm count of rodents but, in contrast, there were indications of enhanced reproduction in a preliminary study on the brown American mink (Neovison vison). In the present experiment the effects of chronic dietary β-sitosterol exposure on the reproduction of the American mink were evaluated with a large number of experimental animals. Male and female finnwhite mink (n = 200) – a previously uninvestigated color type with lower reproductive success compared to brown mink – were exposed to 50 mg β-sitosterol kg−1 d−1 for 10 months and compared with 200 control animals. After 3 months in November, 15 males per group were sacrificed and their biochemical variables determined. The serum glucose and high-density lipoprotein cholesterol concentrations were lower in the β-sitosterol-exposed group, while other effects were minor. The females were mated with the top-rated males (4–5:1) in March and their reproductive performance was determined. The reproductive success increased in the β-sitosterol group with significantly fewer barren females and a higher number of successfully reproducing females than in the control group, which supports previous studies on brown mink and voles indicating that β-sitosterol could be used to enhance the reproductive performance of these mammals.