Estrous mucus discharge in a cow
Keywords: mucus, bovine, estrus, detection, management, dairy, insemination, salt, ferning, crystals
A clear mucous discharge seen at the time of estrus in a cow; an important part of estrous detection in dairy cattle. In some cases, this clear mucous secretion may accumulate in the cranial vagina and be discharged some days after estrus. This mucus contains substantial amounts of sodium chloride (salt). When it is smeared and the salt dries on a glass slide, it generates a so-called "ferning" pattern as seen below.
This mucus is generated by the cervical glands. Therefore, in the case of a persistent hymen, a vaginal mucous discharge is never seen. The mucus accumulates cranial to the hymen where it becomes stained black in color because of metestral hemorrhagic discharges.