Bringing a Mare Back After Pregnancy Loss

A treatment solution of Settle ablates endometrial cups, allowing mares to cycle again.
mare and foal, mares can get in foal after pregnancy loss with Settle injections.
Ablating endometrial cups with Settle allows the mare to cycle again and get in foal after pregnancy loss. | Getty Images

Losing a pregnancy after 45 days inherently spells trouble.  

“Not only do you have to flush out the dead fetus, but you will have a hard time getting that mare pregnant again,” warned Carleigh Fedorka, PhD, assistant professor of Equine Reproduction at Colorado State University, during her Burst Session presentation at the 2023 AAEP Convention.  

Endometrial Cups in Mares

In mares, endometrial cups that produce equine chorionic gonadotropin (eCG) form at about Day 35 of pregnancy. eCG drives the production of secondary corpus lutea, which produce immense amounts of progesterone—the hormone that keeps mares out of estrus.  

Endometrial cups persist for their entire planned life span regardless of what the embryo does.  So, if the mare loses the foal between Day 35 and Day 100, we still have progesterone-producing corpus lutea driven by the cups that stop the mare from cycling back. Those cups persist until about Day 100 to 150. 

“We’ve tried many things to ablate the cups with little success until Settle, a medication traditionally used to treat endometritis,” Fedorka said.   

Ablating Endometrial Cups With Settle

To ablate cups using Settle, you need a team: one person to operate the video endoscope, one person to drive the endoscope within the mare, and one to inject each cup individually. 

The technique involves using a Wang injection needle to inject 1 mL of “treatment solution” (6 mL Settle mixed with 14 mL lactated Ringer’s solution) into each cup. Fedorka said she repeats this procedure seven days later and then ultrasounds the mare to determine if she cycled again. She also monitors the mare’s eCG levels (BET Laboratories).  

To date, Fedorka’s data show this procedure “consistently and reliably reduced eCG by Day 14 following onset of treatment, and eCG levels were negligible by Day 28.” 

Additionally, 80% of treated mares had a pre-ovulatory follicle 24 days after treatment onset.  

Under field conditions, her team has used this protocol on 17 mares thus far, and approximately 75% are currently pregnant.  

If you try this in your own practice, Fedorka asks that you report your findings to, as she is always looking for more data. 

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