Until now, cellular fur animals are in strict dependence on photoperiods in nature, where light is a signal factor of the external environment for them [4]. Unlike other domestic animals, fur-bearing animals have retained a clear seasonality of reproduction (monoestrism) and molting of the hairline, and the light factor acts as a synchronizer of the effects on their body through the optic-hypothalamic-pituitary system. The production of appropriate hormones under the influence of photoperiodism is a tool that regulates the biological rhythms of the animal. The variability in the duration of pregnancy in the wild American mink (Mustela vison Schreber, 1777) is very high – it ranges from 38 to 80 days [1]. The duration of pregnancy in minks depends on the duration of the latent phase of this period. In the farm of OOO «Meha», work is underway to reduce the duration of pregnancy in female minks by artificially lengthening daylight hours at the place where the minks are kept during the gestation of puppies by the females. Stabilization of pregnancy and whelping in this way greatly facilitates the work of fur breeders and livestock specialists, allows you to get earlier litters from females, which contributes to an increase in the safety of puppies and their earlier jigging.