Equine Repro Update

I spent that past couple of days at the Society for Theriogenology annual meeting. If that is a foreign term to you, theriogenology is really just the study of reproduction in animals. This meeting brings together the innovators in this field to present on new and exciting advancements.

One of the most exciting talks I sat in on was discussing the advancements in embryo diagnostics. More specifically, it is now possible to acquire an embryo, biopsy it for genetic testing-either traits or heritable disease-freeze it for indefinite storage and later thaw it for implantation into a recipient mare for her to carry to term. Equine embryos are generally not inherently resilient to manipulation. The group from Texas that presented their advancements in this field have made remarkably astounding advances with embryo biopsy and testing. While much of this is not really commercially available as of yet, just a couple of years ago the levels of success they are now achieving were not even thought possible. Many of these advancements have sprung out of the recent refinement and success of the ICSI procedure, as previously discussed here. Stay tuned.

Another exciting advancement comes out of Colorado. Veterinarians at Colorado State University have developed a PCR test for uterine fungal infections. Uterine infections in horses are usually caused by bacteria. However, on occasion a fungal organism is pegged as the culprit. To this point, fungi have been difficult to reliably culture and identify. Not to mention it can take several weeks to grow them in the lab. This new technology looks for evidence of fungal DNA. They then replicate the DNA in the lab and analyze it to determine the exact type of fungus. This is incredibly useful because results can be achieved in days rather than weeks. Again this test is not yet commercially available, but should be very soon.

Topics that were covered in depth included stallion breeding soundness exams and placentitis. Stallion breeding soundness exams focus on the predictability of a given stallion to be able to produce foals. Despite all of the advancements over the past many years, this still remains a somewhat elusive target. One thing that is becoming increasingly more apparent is that sperm motility does not correlate well with fertility. This goes contrary to historically popular thinking. But the reality is that some stallions have very good motility and poor conception rates, while other stallions have poor motility and yet have reasonable conception rates. That said, we still feel better seeing good motility. The reality is that relating the findings on a breeding soundness exam to future fertility remains ‘complex and multifactorial’- that is medical jargon for we do not yet have a perfect understanding of this. This does not mean that breeding soundness exams are worthless, quite to the contrary. It just means that they are not black and white, and many factors need to be looked at and addressed when considering the current or future breeding soundness of a given stallion.

Researchers continue to explore the complex disease that we have come to call placentitis. Placentitis is an infection of the placenta. The vast majority of the time, bacteria gain entry into the placenta through the cervix of a mid to late term pregnancy. Mares with poor vulvar conformation are particularly at risk. Early identification is crucial to successful treatment. If the injection becomes too extensive the foal can quickly become compromised. The more extensive the infection is the more difficult it is to treat. The best way to look for evidence of a placental infection is ultrasound evaluation of the placenta. This remains our best tool for assessment of placentitis. Treatment usually involves long term antibiotics, anti-inflammatories and progesterone supplementation. There is a lot of new research looking at what are the best medications to use. However, the reality is that successful treatment is tightly correlated with early identification of infection. With this in mind, it may be prudent to screen at high risk mares with ultrasound evaluations of the placenta in late pregnancy.

The last talk I wanted to highlight from this meeting was a presentation by a veterinarian in Argentina who has perfected a large scale embryo transfer program in horses. Embryo transfer is becoming increasing more common. The success rates with embryo transfer continues to improve. The ability to ship recovered embryos to large recipient herds available throughout the U.S. has made this whole venture considerably more practical. There is now an embryo recipient herd here in Michigan (Saginaw) that has been very good for Michigan breeders. The major advantage of a ‘local’ recipient operation is that the cost of shipping and transport of recipient mares is greatly diminished. It also makes it much easier to transport recovered embryos to an ideal recipient because we can now just hop in the car and drive the embryo to its destination, rather than having to rely on the airlines for same day shipment to a recipient herd. Cryopreservation of equine embryos continues to be a challenge. Techniques for improving embryo transfer success and improving efficiencies was covered in great depth.

Even as we are just wrapping up this breeding season, this meeting has reinvigorated me, as I sit in anticipation of next year’s breeding season. The continued advancements in equine reproduction are astounding.