The aim of this study was to analyze the effect of gestational length and multiplicity of mating encounters on selected reproductive parameters within several color varieties of the mink. The material comprised the breeding results of 1285 American mink females of three color varieties: Sapphire, Silverblue, and the Scanbrown. The highest fertility and the highest number of live born and weaned per litter were achieved by Silverblue females. Within all the analyzed gestational length intervals in each color variety, the pregnancies with a length of 45 to 55 days were dominant (78.1% for Sapphire, 75.78% for Silverblue and 64.75% for Brown), while the lowest percentage (3.17% for Sapphire, 6.88% for Silverblue and 3.25% for Brown) represented the pregnancies lasting up to 44 days. The study shows that with an increase in the length of gestation litter sizes become smaller, which is consistent with reports of other authors conducting similar research on this group of animals. We observed an increase in the average litter size with an increase in the number of mating encounters within all analyzed mink color varieties.

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