The aim of this study was to determine plasma concentrations of progesterone and testosterone in blood collected on different dates from pregnant mink of different color varieties. Blood was collected from fourteen pregnant female mink: seven Wild-type Standard Brown females and seven Black females, so called short NAP or Velvet. Blood was collected seven times – the first time before the matings, and the last time in about three weeks before birth. Hormone concentrations were determined by fluorescence immunoassay using the Delfia kits (PerkinElmer, Turku, Finland). Plasma concentrations of progesterone and testosterone differed significantly between collection dates. Significant differences in the concentrations of the hormones were determined also in relation to the color variety of pregnant mink. The concentrations of both studied hormones in the blood plasma of pregnant mink were positively correlated.

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