Effect of blinding on reproductive and pelage cycles in the ferret

Pelage cycle and hair bundle structure in the young and adult ferret, Mustela putorius

The pelage growth cycle and hair bundle structure of three male ferrets, Mustela putorius, as young animals and adults were examined histologically. The follow-up period was 17 months. The growth phase of guard hairs and underfur hairs in follicular bundles was analyzed. Skin samples from the hip were prepared for light microscopy; paraffin sections were cut parallel to the skin surface and stained with a modified SACPIC method. Guard hairs started to develop earlier than underfur hairs. Young ferrets shed hairs between August and mid-November, the guard hairs in three waves and the underfur hairs in one period. In the adult ferrets, guard hair growth peaked three times between June and October. There were individual differences in the summer underfur: growth occurred in one period or in two separate waves. Moulting of the summer coat ended late in October, coinciding with the maximum number of growing winter underfur hairs. In the winter pelage the two hair types matured simultaneously. There was a guard hair in all mature winter coat hair bundles. In addition, all hairs had a medulla.

Seasonal fiber growth cycles of ferrets (Mustela putorius furo) and long-term effects of melatonin treatment

Pelage cycles of ferrets are poorly documented, although it is clear that their timing is sensitive to daylength, mediated by pineal melatonin. Hair follicles were monitored histologically in ferrets from 3 to 19 months of age in order to describe naturally occurring changes in follicle growth status and follicle number over three successive cycles of fur growth. Melatonin was administered to some of these animals in late summer to determine the long-term effects of perturbation of hormonal control. Circulating melatonin was elevated for approximately 50 days by 8-mg continuous release implants. Treated animals grew both their first winter coat, and subsequent summer coats 18 days in advance of untreated controls, but this effect did not extend to the second winter coat. Reimplantation the following year induced an advancement of the autumn follicle growth as in the 1st year. Autumn fiber growth occurred at similar times in untreated males and females, and response to melatonin did not differ between sexes. Hair follicle regression and shedding during the natural spring molt was also contemporaneous in males and females, but fiber regrowth occurred 4-6 weeks later in males as compared with females, suggesting that reproduction-related factors affect fiber growth initiation, and that fiber growth and shedding are physiologically distinct processes. Melatonin implants in autumn also affected reproduction in the spring, advancing oestrus by 3-4 weeks. These results show that interference with photoperiodic and hormonal control mechanisms in ferrets can affect pelage and reproductive cycles for up to 10 months.