Breeding mares has been accomplished for a long time but recently we’ve discovered some useful techniques to help increase reproductive efficiency in mares.
A few years ago new artificial insemination techniques (AI) using an endoscope were first described. An endoscope is a flexible fiber optic scope allowing veterinarians to see deep inside the uterus. For more information on this topic see our article on
“Endoscopic Assisted AI in Mares”.
An even newer report shows the value of endoscopy for examination. Traditionally, uterine biopsy, or taking a small sample of the uterus and looking at it microscopically has been the standard method for evaluating uterine scarring or fibrosis. Uterine fibrosis is a consequence of age and pregnancies. Although a natural consequence of foaling and age, it impacts some mares more severely. With an increase in fibrosis the ability of the uterus to maintain a pregnancy decreases and uterine biopsy results usually report the probability of a mare becoming pregnant and keeping a foal to term. It was recently described that endoscopic viewing of the small arteries of the uterus can predict fibrosis as well as biopsy. With more experience we will hopefully see this non-invasive technique used to determine fibrosis without waiting the weeks for the biopsy report to be returned. Previous to this paper some veterinarians including this author have utilized the endoscope to examine the uterus; this method may add a powerful new diagnostic technique.
Thyroid hormone has often been rumored to be critical in mare reproduction despite any clear or proven scientific relationship. Veterinarians conducted a large study involving 329 broodmares up to day 15-16 of pregnancy. There was no significant relationship between blood thyroid levels and pregnancy. Some of the mares in the study were supplemented with thyroid hormone and in those mares there was no relationship between this supplementation and pregnancy. Old habits die hard, especially in the equine world but perhaps this and other studies like it will eventually end the unnecessary practice of adding thyroid hormone to pregnant mares.
Following breeding it’s well established that mares have a transient endometritis or uterine inflammation. This inflammation is needed because only one sperm is needed for pregnancy and billions must be evacuated from the uterus. When present this inflammation, if severe enough, can be quite damaging to sperm. This inflammation peaks at approximately 12 hours and in the normal mare is completely gone within 48 hours after breeding. One consequence of breeding with frozen semen is a pronounced post breeding endometritis in many mares. Because breeding with frozen semen requires AI very close to ovulation it’s always been a dilemma as to how soon after the first breeding could you safely AI and avoid the problems associated with endometritis. Part of this puzzle has been answered. It was recently reported that normal post breeding uterine inflammation isn’t severe enough to disturb sperm if the second dose is deposited within 6-10 hours of the first. This means that repeat AI with frozen semen a short time after an initial breeding is not a waste of time or money. For more information see
“Breeding With Frozen Semen."
Many breeders use oxytocin or prostaglandins after breeding to help the uterus contract, evacuate extra sperm, and minimize post breeding endometritis. It was recently reported that the use of prostaglandins will lower progesterone levels and pregnancy rates in the mare. Progesterone levels are critical to maintain pregnancy and the use of prostaglandins as a post breeding treatment is discouraged.
Breeders have long known that putting the mare under lights in November will usually result in a mare cycling when the breeding sheds open in February. Recent research has shown that using the drugs domperidone and sulpiride along with light can shorten this time by up to 2 weeks. Seventy five percent of mares put under light on January 1 and treated with sulpiride ovulated within 40 days. Mares just put under lights ovulated 2 weeks later. This treatment regimen can prove to be valuable to the breeder desiring an early foal.
Equine reproduction is slowly becoming a more successful endeavor. Many times we hear things which are later refuted. Both of these facts are reason enough to keep current with the latest in research. Over time proven techniques stand up to repeated evaluation and reevaluation. Our hope is that this short article will help you keep up with current news in equine breeding.
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