Current topics in Equine reproduction: the Mare November and December saw 2 well attended meetings in which equine reproduction was discussed from many perspectives. The American Association of Equine Practitioners held its annual meetings with many hours devoted to equine reproduction and the West Coast Equine Reproduction Symposium hosted 2 additional days of lectures. We'll cover some pertinent information transmitted at these meetings as well as other relatively new and interesting topics. This month we'll cover the mare, next month stallions. Endoscope assisted Reproduction Last year new techniques in artificial insemination (ai) using an endoscope were described. An endoscope is a fiber optic flexible scope allowing veterinarians to see deep inside a structure like the throat or the uterus. For ai to improve pregnancy rates in normal and sub fertile mares When using endoscope guided ai one can utilize 2 types of techniques depending on the type of mare. Ai close to the utero-tubal junction resulted in more sperm in the oviducts (the site of fertilization) compared to traditional ai at cervix-uterus location. Also when sperm were deposited using an endoscope so that the utero-tubal junction could be visualized higher pregnancy rates were achieved. Others have showed that motile morphologically normal sperm are selectively more able to enter the oviduct where they fertilize the egg. The most commonly used ai techniques recommended an insemination dose of 500 million sperm be deposited at the junction where the cervix opens into the uterus (cervico-uterine junction). Using endoscope guided ai doses as low as 5 to 25 million sperm are used. Although this endoscope-guided technique resulted in lower pregnancy rates than usual, it opens up great new option for sub fertile mares that have marked uterine inflammation following ai. The low doses allow us to decrease this inflammation and possibly help these mares become pregnant. Another use of low volume ai is with the sub fertile stallion that produces low numbers of sperm. This technique will be helpful in increasing these stallions’ pregnancy rates. To evaluate uterine health Uterine biopsy, or taking a small sample of the uterus and looking at it microscopically has been the traditional method for evaluating uterine scarring or fibrosis. Fibrosis is a consequence of age and many pregnancies. With the increase of fibrosis the ability of the uterus to maintain a pregnancy decreases. It was reported last year 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 adds a powerful new diagnostic technique. Thyroid levels and early pregnancy 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. Breeding with frozen semen 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. Last year it was 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. Prostaglandin injection and progesterone levels Many breeders use oxytocin or prostaglandins after breeding to help the uterus contract, evacuate extra sperm, and minimize post breeding endometritis. This year it was 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. Shortening the transition period with light and pharmaceuticals. 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. Foal heat breeding Foal heat usually begins 5-12 days post foaling, with most mares ovulating by day 21. Through the years many conflicting things have been said about foal heat breeding and run the whole gamut from "always breed on foal heat" to "never breed on foal heat". Historically mares bred at foal heat had pregnancy rates 20% lower than mares bred later. New research shows that if mares are looked at as individuals they usually fall into a few basic categories upon which sound breeding decisions can be made. When looked at as a “group” mares bred on foal heat have about 20% lower pregnancy rates than mares bred at later cycles. Recent research involving hundreds of mares bred artificially showed that if mares were bred properly on foal heat their pregnancy rates were comparable to maiden, and mares without foal at side. Other researchers have shown similar research and what is becoming quite evident is that following foaling mares can not be "grouped" into one large category. In other words, the decision to breed on foal heat should not be based on your previous experiences with foal heat breeding, "common knowledge", or even the mares previous history. Instead the decision to breed post foaling should be based on the individual mare and her specific condition following foaling. Several factors are critical in the decision to breed on foal heat or not. They all revolve around the health of the uterus and to a physiological process known as uterine involution. Uterine involution is the process of the uterus shrinking in size, becoming more capable of muscular contraction, and evacuating all the fluid associated with pregnancy. Normal mares will contract their uterus from the large size capable of holding a foal to one that is often less than 6 inches in diameter. Involution and muscular contracting ability of the uterus are key in the ability of establishing the next pregnancy. One very interesting new finding is that mares that are exercised have a dramatically better involution with better evacuation of pregnancy associated fluids than stall confined mares. Take home message: make sure those post foaling mares get lots of exercise! Some veterinarians recommend uterine treatments to improve pregnancy rates in foal heat mares. These treatments include antibiotics, hormones (oxytocin and prostaglandins - to improve uterine contraction), and lavage (to physically evacuate uterine fluid). These treatments have been advised either on the day of or shortly following foaling. Unfortunately the benefit of these treatments post foaling is unreliable and inconsistent when scrutinized with controlled research. Some general guidelines have been shown to increase pregnancy rates and breeding efficiency in foal heat mares: Treat each mare as an individual, what will work for one will not necessarily work for another Have the mare examined daily starting on day 6 or 8 after foaling. Don’t breed the mare earlier than 10 days post foaling. If the mare has fluid in the uterus when bred it will lower pregnancy rates. Breed mares one time during foal heat (obviously close to ovulation). Post breeding treatments are valuable in foal heat mares; they include uterine lavage and oxytocin for uterine evacuation, and uterine antibiotics. Mares who had dystocia or retained placenta are usually not good candidates for foal heat. Check foaling mares early in the season. If it’s possible don't wait until late in the breeding season (May) to breed. Time is running short. The first breeding is often the best chance; repeated attempts frequently result in residual inflammation. 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. Cascade Horseman, Feb 2002.