AAEP Reproduction Coverage: Road Map to Pregnancy

closeup of a mare and her foal on green grass

If you attended this popular Table Topic at the 2022 AAEP Convention, you’ll recall—perhaps with an unexpected mixture of awe, disbelief or anxiety—the slide projected on the screen at the front of the room labeled “Road Map to Pregnancy.” If you weren’t there, imagine a flow chart with approximately 40 text boxes containing notes in eight-point font with arrows coursing in every direction possible that, of course, all ultimately lead to a live foal.  

Ryan Ferris, DVM, DACT, from Summit Equine Inc., in Gervais, Oregon, a co-moderator for the session, admitted to attendees that the chart was “a little overwhelming.” He assured the vets in the room it was meant only as a guide. 

“This chart is a wonderful summary of the requirements for a mare to become pregnant or not pregnant; including diagnostics, treatments, and normal and abnormal physiology,” said Ferris.

Jumping straight into oncoming traffic, Ferris began the session by stating that obtaining a detailed history is of the utmost importance when working up a mare. 

“That way you don’t repeat procedures and try to reinvent the wheel,” advised co-moderator Karen Wolfsdorf, DVM, Dipl. ACT, from the McGee Fertility Center, Hagyard Equine Medical Institute. “We want to use the knowledge gained from a thorough history and take things a step further.” 

History in the Making

To get the ball rolling, Ferris began by asking: “What characteristics make a mare be considered a problem mare? 

The audience then suggested obtaining the following information:

  • What stallion are they using?
  • Are they using the same stallion, or have they tried others? 
  • Has she ever been pregnant or had a foal?
  • What is her general health? 
  • Has she been tested for pituitary pars intermedia dysfunction or equine metabolic syndrome? 
  • Is she on any medications at the moment (e.g., a show horses “coming in hot”)? 
  • How are you planning on breeding her—fresh, cooled or frozen semen; embryo transfer; or ICSI (intracytoplasmic spermatic injection)?

“In addition, knowing the owner’s financial expectations and why they want to breed the mare may also be important,” said Ferris. “Is it for sentimental or economic reasons? Practitioners need to be realistic with clients of how much it may cost to obtain a pregnancy from their mare.”

Culture and Cytology

Ferris and Wolfsdorf asked attendees: “Who are you culturing? All barren mares from last year? Are you doing cytology as well?” 

Many practitioners in the room indicated they do both endometrial cultures and cytologies

Wolfsdorf said, “I don’t do a cytology with normal maiden mares or mares that just require a culture for the breeding shed unless there is an abnormal finding on examination or a history of endometritis, not getting in foal, or losing a pregnancy. In these cases, doing a cytology gives you additional information down which path to proceed.”

That said, each breeding shed has different requirements for uterine culture prior to breeding. A uterine culture ensures the mare has been seen by a veterinarian, is disease-free, is not transmitting disease to the stallion, and has the best per-cycle pregnancy rates possible. 

“It is important when mares do not get in foal not to assume that the lack of intra-uterine fluid on ultrasound means the uterus is free of infectious organisms,” stated Wolfsdorf. “I’ve had maiden mares not get in foal and then identified with an underlying Pseudomonas spp. infection after the infusion with acetylcysteine. This will break down mucous and biofilm revealing the bacteria on culture and cytology.” 

Infusing Misoprostol onto the Oviducts

Administering misoprostol might accomplish two results with one treatment: unblocking the oviducts (potentially) and identifying bacteria.

“By administering misoprostol, you’re potentially activating bacteria, creating inflammation and producing intra-lumina fluid,” explained Wolfsdorf. “With a low-volume lavage, culture and cytology bacteria may be identified. The misoprostol application can be used in either estrus or diestrus, which is convenient.”

One audience member asked if the moderators recommended breeding on the same cycle as the treatment with misoprostol. Ferris said he often does treat the mares with misoprostol and breed the mares on the same cycle. Some attendees agreed saying that they go back the day after treating with misoprostol and lavage the mare’s uterus and breed on that cycle.

However, Wolfsdorf said, “If their culture and cytology on low-volume lavage is positive, I don’t breed the mare the same cycle as the misoprostol treatment. Instead, I treat the mares and short-cycle them.”

Uterine Biopsy

For suspected deeper-seeded infections, veterinarians should consider a biopsy.

Ferris said, “I am using endometrial biopsy more than in previous years due to increased information gained on the mares I am managing. Every year I am surprised by my findings on endometrial biopsy that I would have missed with other diagnostics. I think this is a tool that we are not using enough.”

Wolfsdorf added, “In the mare that is to carry her own pregnancy or produce an embryo for embryo transfer, a biopsy helps identify underlying pathology. The mare can then be treated accordingly. For example, if there is inflammation, determining the cause and treating it will improve her prognosis. Or, if dilated lymphatics are identified, uterine clearance will be an issue and appropriate therapy can be initiated.” 

In addition, Wolfsdorf explained that the biopsy results can make a difference when a practitioner is trying to decide if a mare can carry the pregnancy to term or if embryo transfer might be a better option for the mare. 

If veterinarians perform biopsies, the moderators both strongly advised sending them to a boarded theriogenologist. The theriogenologist can then make additional diagnostic and/or treatment recommendations according to the pathology identified.  

“The 40- or 50-year-old endometrial biopsy grading system can be confusing,” explained Ferris. “Rarely are mares classified as a grade 1 or a grade 3, but commonly a grade 2A or 2B. Getting the comments on the report as to why this mare’s endometrium is a 2A or 2B is important in determining further diagnostics or therapeutics for this mare. The overall grade is not as important as the abnormalities detected. Again, this is where a theriogenologist helping interpret the endometrial biopsy sample can be really helpful in generating a recommendation and/or treatment plan for your mare.” 

Treat, Quit or Change Tactics

There are many diagnostics and treatments that practitioners can reach for when addressing reproductive issues in the mare. On the whole, practitioners agreed that when selecting treatments, all veterinarians should proceed with good antimicrobial stewardship. Alternatives to antibiotics mentioned during the sessions included non-antimicrobial biologics (platelet-rich plasma, mesenchymal stem cells, immunomodulators and chemical curettage). 

“Kerosene can be used in mares with suspected biofilm,” explained Wolfsdorf. “It removes the surface epithelium and allows us to get to the glands, identifying the bacteria and their sensitivity before treating with the appropriate antibiotic and adjunct therapy.” 

At the end of the day, attendees wanted to know, when should they stop trying to breed a particular mare? When the breeding season ends? When the owner runs out of money?

Some practitioners indicated they try for two cycles before significantly changing approaches. Wolfsdorf said she approaches each cycle differently, trying something new for three cycles before she changes the stallion. Each mare is an individual, and decisions should be based on that and the owner’s economic and emotional desires. 

Ferris reminded practitioners that despite having all these options available, “Sometimes we can overdo our treatment strategies, and less treatments may be best. Additionally, the mare has zero chance of getting pregnant if the mare is not bred.” 

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