Premature ovarian failure in a 16‐year‐old warmblood mare

Summary Ovarian failure has been recognised in old mares, usually older than 19–20 years old; however, in equine, little information is available about premature ovarian failure, which refers to the occurrence of ovarian senescence at ages younger than expected. The present case report describes a 16‐year‐old mare with a history of infertility as well as intrauterine fluid accumulation during oestrus and ovulation disorders in the years before referral. At referral, the mare was examined using transrectal ultrasonography and it had no follicle larger than 15 mm on the ovaries. Thereafter, the ovaries of the mare were transrectally examined periodically, but there was no evident change in the follicular growth on the ovaries even after a period of treatment with buserelin for stimulation of follicular growth. In addition, blood samples were collected from the mare for measurement of serum anti‐Müllerian hormone (AMH), as an indirect marker of ovarian reserve, at referral as well as before and after treatment with buserelin. Additionally, blood samples were collected from cyclic mares (during breeding season) and deeply anoestrous mares (during non‐breeding season) for assessment of serum AMH. Although AMH was detected in both cyclic and deeply anoestrous mares, it was not detectable in any of the samples derived from the mare with inactive ovaries. In conclusion, considering the inactive ovaries, undetectable serum AMH and the age of the mare, this case was diagnosed with premature ovarian failure probably due to diminished ovarian reserve.