<div>Background: The overpopulation of free dogs represents a risk to public health in some countries. However, current strategies for its control are insufficient; it is convenient to devise new alternatives. 
 
Methods:&nbsp;To determine the effects of a single oral administration of coumestrol (COU) on vaginal epithelial cells, serum progesterone and estradiol levels and clinical parameters: periovulatory bitches received a biscuit that contained 600 mg COU/kg diluted in DMSO or with DMSO alone or without additives. Each group was subdivided into animals that had ovulated on day 0 and those that had not.&nbsp; 
 
Result: In animals that ovulated, COU did not affect hormonal profiles. In contrast, animals that did not ovulate showed lower circulating P4 concentrations on days 21 and 28 after treatment than the control group. Furthermore, COU reduced parabasal cells and increased superficial anucleate cells. COU and DMSO are estrogenic and their actions depend on the ovulatory status of the animals.</div>

Administration of Coumestrol and/or Dimethyl Sulfoxide Affects Vaginal Epithelium and Sex Hormones in Female Dog