Effects of equine chorionic gonadotropin on reproductive performance in anestrous mink

The incidence of anestrous mink during the normal breeding season has been reported to be as high as 5%. We sought to induce estrus in these mink by using various doses of equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG). Seventy-five female mink maintained under standard ranch conditions failed to demonstrate estrus during the annual breeding season in March. These anestrous mink were randomly assigned to treatment groups. Treatments were given on March 16 and again on March 18. On these 2 d, mink were treated with equal doses of saline, 25, 50, or 100 IU of eCG, or 50 IU of eCG on March 16 and 50 of IU of eCG + 100 IU of hCG on March 18. Females were paired with males beginning on March 22. None of the saline-treated mink mated. In contrast, reproductive performance of the anestrous mink was significantly improved by treatment with eCG. This included proportion of mink breeding (47 to 100%), proportion giving birth (33 to 80%), and average litter size (2.6 to 4.0 kits per whelping female). Reproductive efficiency improved with increasing doses of eCG and was not further improved by addition of hCG. These results demonstrate that eCG has a potential application for treating anestrous mink during the breeding season.