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Equine Reproduction

Equine Reproduction

  1. My 6-year-old mare has significant discomfort with ovarian follicles and has responded well to Regumate, which she has been off for 18 months. She is VERY "mareish" but when not in season, solid minded and athletic. I'd like to breed her with a stallion known for his calm and consistent demeanor, outstanding genetics, and overall sound health/mind. Given my mare's ovarian issues, is there anything I need to be aware of? Is breeding her possibly unsafe and/or unwise? (View Answer)

    Many mare owners complain of inconsistent work ethic, back pain and changes in attitude during the time of year that their mare is actively cycling. Most of the time there is no specific problem with the reproductive system of the mare that would make it unsafe to breed. Prior to finalizing your decision to breed your mare, you should have a breeding soundness examination performed by a veterinarian experienced with equine reproduction. This examination will answer your questions about the health and fitness of her reproductive tract and alert you to any problems you may encounter along the way. Wishing you all the best with your mare! Terri Van Wambeke, DVM, Oregon City, Oregon

  2. My 14 year-old Thoroughbred was easy to get in foal until after her 4th (extremely large) colt. Since then (three years ago), her biopsy graded as IIB and she typically holds fluid post breeding. Are there any new protocols for settling such mares? I’m ready to pull the plug if we’re unsuccessful this year. Is Breed assist an option to improve her chances? Live cover is so harsh and an archaic protocol. (View Answer)

    Endometrial biopsies are graded I, IIA, IIB and III, with each successive progression in biopsy grade holding different statistics for conception and pregnancy loss. As the grade increases, the chances for pregnancy decrease and the amount of inflammation, presence of scar tissue and odds of persistent uterine infection increase. The presence of scar tissue is not treatable but the presence of infection can be addressed, and in some cases may improve the biopsy score. A grade IIB biopsy is indicative of moderate inflammation and scar tissue formation with a 10-50% chance of carrying a foal to term. As you can see this is a fairly wide range.


    Additional testing is recommended to give you a better picture of the chances of your mare carrying a foal to term, and would also indicate if any treatment would be necessary prior to breeding. These would include: external genital conformation evaluation, ultrasound exams, speculum exam to look at the integrity of the cervix and check for urine pooling or fecal contamination, uterine culture and cytology and low volume lavage cytology. It is difficult to answer questions about new protocols without knowing the answer to why your mare is having problems. The protocol for treatment or breeding management changes depending on the exact problem the mare is experiencing.


    Keep in mind, semen quality and the breeding management of the mare play a large part in any successful breeding program. You may want to consult with a boarded equine theriogenologist or a veterinarian with extensive experience working with mares having breeding difficulties for additional management strategies. It is possible to get some of these mares successfully carrying to term but it requires client commitment and intensive breeding management. Wishing you and your mare a successful outcome! Terri Van Wambeke, DVM, Oregon City, Oregon

  3. My mare has never carried live to term. Her last breeding was with many injections that I know nothing about. The end result was an abortion and mare with bladder leakage. She seems to be in heat all the time and is very uncomfortable. The veterinarian is not knowledgeable to know what steps to take next and insists on more testing. She will not be bred again as it is too stressful and just doesn't work. Any suggestions to make her more comfortable? (View Answer)

    It sounds like your mare suffers from vesicovaginal reflux also called urine pooling or urovagina. This is due to a conformational defect in the mares reproductive tract, either primary, or secondary to other causes such as severe weight loss, trauma, aging, large uterus or improper Caslicks procedure. When the mare urinates, some of the urine collects in the vaginal vault near the cervix causing inflammation (vaginitis and cervicitis). This urine then enters the uterus, particularly during estrus, when the cervix is relaxed in preparation for breeding. Urine in the uterus creates inflammation and an environment for the development of infections (bacterial and fungal). Furthermore, the presence of urine makes any sperm deposited unlikely to survive, and the presence of urine and inflammation make the environment unfriendly for an embryo.


    That said, urine pooling causes persistent inflammation in the uterus of the mare. This creates a situation where, due to the chronic ongoing inflammation in the uterus, the lining of the uterus (endometrium) releases a hormone called prostaglandin. Prostaglandin adversely affects the development of corpora lutea on the mare’s ovaries. Corpora Lutea are responsible for the production of Progesterone. Progesterone is very important for the maintenance of pregnancy and the normal inter-estrus interval. Mares with persistent inflammation will not be able to maintain a normal pregnancy and will often “short cycle”.  Owners with mares that short cycle complain that the mare is always in season because they are not experiencing the average 21 day estrous cycle.


    I recommend that you consult with a veterinarian experienced with equine reproduction. A speculum examination of your mare, best during estrus, combined with a thorough reproductive tract examination should give you some answers. The veterinarian will likely need to to do some diagnostics and take some samples from the uterus for evaluation. If an infection is confirmed it will need to be treated. Once your veterinarian has made a diagnosis, you can consult with a surgeon or equine theriogenologist to determine if your mare is a candidate for a surgical repair to prevent reoccurrence. I hope you are able to make your mare more comfortable, good luck to you both. Terri Van Wambeke, DVM, Oregon City, Oregon

  4. My foal had a low IgG that was under 400. My veterinarian gave less than one 1000 mL bag of plasma and the foal crashed two days later. I spoke to another equine veterinarian that informed me with that low level of IgG the foal should have received two to three bags of plasma. I wonder if this is correct before I make a complaint about my veterinarian? (View Answer)

    When a foal has an IgG lower than 400 after 24 hours of age (this is called Failure of Passive Transfer) , the standard of care is to administer intravenous immunoglobulin. The amount of product to administer depends on a few things. First, not all equine plasma products for the treatment of failure of passive transfer are the same. The range of increase in circulating IgG after administration of approximately one liter of plasma is 250 mg/dl to 600 mg/dl. Recommendations for IgG levels after administration of plasma depend on the foaling conditions and environment of the foal. In an otherwise healthy foal without foaling complications in a very clean environment, an IgG level of 400 mg/dl might be acceptable and this would be the minimum standard. In a high risk foal that experienced foaling complications and/or residing in an environment that is not very clean or has a history of infectious disease, the recommendation would be for a higher IgG level, possibly over 800 mg/dl. The questions that you should ask your veterinarian to clear things up would be: Was the foal considered high risk for infection? What was the IgG level after administration of the plasma? Did the foal have a reaction to the plasma during administration that made it unsafe to continue or to administer additional product?


    If the foal was otherwise healthy and “low risk”, and the circulating IgG levels post administration of plasma were 400 mg/dl or greater, then administration of one liter of plasma likely would have met veterinary standard of care for this situation. Unfortunately, there are many reasons that foals become very ill in the first few days of life. I recommend you have a conversation with your veterinarian to discuss your concerns prior to making a complaint. You don’t want to damage an otherwise good relationship with your veterinarian over an issue that may have been out of their control.  Nobody ever wants to lose a patient. I am very sorry for your loss and I hope you are able to get your concerns addressed. Terri Van Wambeke, DVM, Oregon City, Oregon

  5. I know my veterinarian has to ultrasound my mare to determine the follicle size. However, how soon is a mare, after being given a shot to short cycle, capable of breeding via artificial insemination? (View Answer)

    Assuming that your mare had a functional corpus luteum on her ovary that was old enough to respond to a luteolytic agent, this is typically day five after ovulation, the size and number of follicles on her ovary at the time that the luteolytic agent is given will determine when she is next likely to ovulate. As a general rule, most mares will come back into heat within 3-4 days of the injection and ovulate within 7-10 days.  Prior to administering the luteolytic agent (the short cycling injection), the mare should have an ultrasound examination of her uterus and ovaries completed. This exam provides some important information. Does the mare have a functional corpus luteum? Is the mare pregnant? What size and number follicles are present on the ovaries? The larger the follicle is when the luteolytic agent is given, the sooner the mare will ovulate. If the mare has a very large follicle present when the injection is given, that follicle can ovulate without the presence of the other indicators of impending ovulation and be unable to produce an embryo, it can become a fertilizable ovulation or it can regress, in which case new follicles will begin to develop on the ovary and those will need to be tracked. So, the estimate of the breeding date will depend on the results of the ultrasound exam completed on the day your mare is given the luteolytic agent. Terri Van Wambeke, DVM, Oregon City, Oregon