drjustinhigh eh

Horse Breeding Season Is Here!

In Texas, May marks the high point for breeding season, and I hope yours has gone well so far. Equine reproduction is one of the aspects of veterinary medicine where technology has played a major role in helping Mother Nature along, but even so, there can still be some ups and downs when getting mares in foal. If you are in the predicament of being more than halfway through the season with nothing more to show than an empty uterus and a stack of bills, this may be of some use.

 The mare side

The first thing you can be reassured of is that mares cycle better in the longer daylight hours and warmer temperatures of the spring versus the often inclement and unpredictable weather of February and March. Many horse owners send mares off to the breeding farm early to get a jump on the season with less than ideal results due to erratic or transitional cycles. Now, being certain your mare is cycling normally, we need to focus on what can be done to ensure your mare’s uterus is not the problem. Having a simple uterine culture and cytology done for each cycle you breed helps identify infection and inflammation that will consistently prevent conception.

Uterine biopsy is a useful diagnostic tool for older mares or ones with more chronic issues.  Biopsy results can be helpful in the diagnosis of disease, as well as a determinant for mares that are no longer able to carry a pregnancy and may be changed to embryo transfer. While performing a rectal ultrasound, your veterinarian can identify other potential problems.  Endometrial cysts can, if large enough, prevent some of the signaling mechanisms for a pregnancy to survive.

Cysts can, by a variety of ways, be removed but are best done soon after foaling to limit the recovery time during breeding season. Infection or inflammation often causes the uterus to produce fluid, which is one of the more common and troubling issues to overcome when breeding mares. Mares with large pendulous abdomens or poor perineal conformation are prone to retain fluid and can allow urine to reflux into their uterus compounding existing problems. This is where pre- and post-breeding lavages are critical, to remove abnormal fluid and quiet inflammation. Judicious use of intrauterine and systemic antibiotics/anti-inflammatories is an integral part of the lavage schedule.

The stallion side

When it comes to mares not settling, the stallion is usually the first one to get blamed. For mare owners, the stallion side of the equation is more difficult to control, especially when breeding with shipped semen. To protect mares, I breed with shipped semen. The first thing I do after opening the shipping container and evaluating motility is to culture a sample for bacterial growth. It is not uncommon for stallions to have bacterial contamination of their semen, and when allowed to grow in extender for the time of shipment, you may be setting your mare up for infection. Most commercially prepared semen extenders contain antibiotics, but not all bacteria are susceptible to them. More often than not, the issue of stallion fertility comes down to overall semen quality, not necessarily infection. Basically, how many sperm cells do you have to work with, and what is their progressive motility? This is where doing your homework about the stallion to which you’ve chosen to breed comes in. Some stallions produce low numbers of usable cells but have exceptionally good motility. Other stallions may have high sperm cell production, but when they are viewed under the microscope, they look like nap time at the old folks home.

Understand, we as Quarter Horse breeders haven’t always selected for fertility over the years, so if the best cross for your mare has less than desirable semen quality, try your best to accommodate the situation. Mares typically have better conception rates when bred with fresh semen. This may mean the best option to get around a semen quality issue is to send your mare to the stallion station rather than shipping semen to her. This thought process works the same when breeding with frozen semen as well. Closer to the source is always better.

Many stallions with lower fertility breed full books of mares due in large part to the advancements in technology like centrifuging semen at high speeds to remove dead cells, debris and seminal plasma that in many cases limit conception. Other stallions require advanced techniques such as deep horn insemination or endoscopy to obtain pregnancies. I’m sure not suggesting you go tell the stallion manager how to do their job, just being informed about the processes available to increase fertility will get you well ahead of the pack.          

After all this, I do believe there is such a thing as an incompatible breeding. Many times when everything looks good on paper, but you just cannot get a pregnancy think about changing stallions. You’d be surprised how many times that works. In the end, though, I’m convinced the two most important things you need to breed mares are patience and money. Unfortunately, one usually runs out before the other.  

drjustinhigh eh Justin High, DVM Dr. Justin High is a veterinarian and partner in Reata Equine Hospital in Weatherford, Texas. He graduated vet school from Texas A&M University and completed an internship at The Littleton Equine Medical Center in Denver, Colo. High’s years of practice focuses on the Western performances horse. Send any comments or questions to justinhighdvm@reataequinehospital.com.

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