A Happy New Year to you and yours from the team at Rocky River Large Animal. We wanted to use this newsletter to start the year off right and help those of you wanting to have your mare bred this year. Whether you’ve done it countless times, or are new to horse breeding, we hope this newsletter can provide you with useful information.

Steps To Take Before Breeding Your Mare

1. The very first step when it comes to breeding your mare is for you to decide whether or not she is suitable for breeding. Does she have good temperament? Is she up-to-date on vaccines? Does she have good conformation? Are there any underlying diseases? Does she have undesirable genetics that could be passed onto the foal? How old is she? An older mare (15+ years old) will have a much more difficult time getting pregnant than younger mares and those that have foaled before.
2. The next step is to consider the time and financial commitment associated with breeding a horse. Along with the inherent stud fee, there is also tracking the horse’s cycle. To correctly time insemination, tracking a horse’s cycle will likely require multiple farm calls and reproductive ultrasound exams. There are also the additional costs of follow-up ultrasound exams to confirm pregnancy and additional vaccines to avoid unwanted abortion. The expenses associated with breeding your horse can increase fast, not to mention the cost associated with foaling. You will first invest in the breeding and foaling but also need to consider the time and resources associated with raising and training that foal for years to come.
3. If you’ve decided your mare is suitable for breeding and you understand the cost associated with horse breeding, then the next thing to look into is the stallion. When selecting your stallion, ensure that his genetics match well with your mare and his credentials meet your standards. Then you have to find out how your mare will be bred by the stallion. The first option is natural cover, meaning she’ll have to be transported to be bred by the stallion on site. The other option is artificial insemination (AI) via chilled or frozen semen. In which case you’ll need to find out how many days it will take to order the semen in advance to ensure she is inseminated at the right time to maximize her chance of getting pregnant.
4. Contact your veterinarian to have a breeding soundness exam performed.

Have A Breeding Soundness Exam Performed

When it comes to setting up your mare for a successful breeding season it’s important to have her evaluated by a veterinarian before things get underway.

1. History:
   1. Underlying Disease: As part of the breeding soundness examination we’ll look for potential underlying disease processes that could affect breeding success or put your mare at risk during pregnancy. Such disease processes could include Cushing’s or Equine Metabolic Syndrome which could predispose your mare to laminitis during pregnancy and cause reduced fertility due to abnormal hormone regulation.
   2. Vaccinations: As part of the breeding soundness exam we’ll ensure your mare is up to date on core vaccinations to minimize risk of infection during pregnancy.
   3. Previous Reproductive Success: During this exam we’ll also discuss previous reproductive issues and success to help ensure an efficient breeding.
2. Physical Exam:
   1. Body Condition Score (BCS): During this exam we’ll assess body condition to ensure your mare is neither too thin nor too fat. An overly thin mare (BCS <4/9) will have trouble cycling appropriately due to her body being in a calorie deficient state. An overly obese mare (BCS >7/9) is more likely to have early abortion. Therefore, it’s recommended to keep your mare at a BCS of 5-6 out of a 1-9 scale for the best results. Check out a previous newsletter discussing how to body condition score your horse.
   2. Conformation: We’ll look at anatomical conformation of the horse and make you aware of any undesirable bodily traits that could be passed onto offspring. We’ll look for lameness and arthritis, as this may reduce fertility and become exacerbated during gestation.
   3. Foot Health: We’ll also look at foot health to ensure the horse can comfortably sustain the added weight and stress of a foal. As stated earlier, laminitis can be detrimental to a pregnant mare so we’ll look to ensure that no previous subclinical bouts of laminitis have occurred, predisposing her to future laminitis.
   4. Dental Exam: We’ll take a look at the horse’s dentition to make sure the teeth are in good condition to comfortably consume the added calories she’ll need to maintain weight during pregnancy and lactation.
3. External Reproductive Exam: A portion of the physical exam will be taking a look at the external portion of the reproductive tract of the mare. This means we’ll lift the tail to look at her perineal conformation, because a mare with a tilted vulva will have more difficulty maintaining a pregnancy. This can lead to more frustration and expense when it comes to getting your mare pregnant. After looking at the most external barrier to keep bacteria out, we’ll then look at the second barrier that helps to keep bacteria out. This is known as the vulvovaginal sphincter and it is assessed by inserting a speculum and assessing its competency. An incompetent sphincter will allow for air and fecal aspiration into the vagina which may be termed “wind sucking” .
   1. Caslick’s: A way to combat this angled perineal conformation and/or incompetent sphincter to help with establishment and maintenance of pregnancy is to perform a Caslick’s procedure. This procedure is when the top 2/3 of the vulva are sutured together to prevent exposure to air and bacteria while still allowing urine to exit.
4. Internal Reproductive Exam: The next step of the exam will be to look at the internal reproductive tract of the mare.
   1. Cervix: The cervix is important to assess looking for scarring and damage to the cervix from previous foaling as well as inflammation that could be present from urine pooling. This can be done via digital palpation of the cervix along with visualization via vaginal speculum and flashlight. Looking and palpating the cervix will also indicate where the mare is at in her cycle. A relaxed cervix will indicate a mare is in estrus while a tightly closed cervix is indicative of a mare in diestrus.
   2. Ultrasound: Rectal palpation will be performed next to assess the internal position of the uterus and ovaries. Ultrasound must also be performed as rectal palpation alone will not provide the full story of what’s going on in the uterus and ovaries of that horse.
      1. Uterus and Ovaries: Ultrasound will help to give a baseline exam of both the uterus and ovaries of the mare to help determine where she is at in her cycle.
      2. Uterine Cysts: Ultrasound can help identify uterine cysts which reside in the lumen of the uterus. This can help identify their location prior to breeding to help differentiate them from early pregnancy along with looking for excess numbers of them or excessively large cysts that can affect pregnancy maintenance.
      3. Abnormal Uterine Fluid: Finding fluid present in the uterus can indicate presence of bacteria, delayed uterine clearance, and/or failure of cervical relaxation. If the mare is older it may indicate fibrosis of the uterus causing decreased uterine clearance. Depending on how the fluid looks on ultrasound and how much fluid is present, different courses of action in regard to diagnostics, treatment, and management may be indicated.

5. Uterine Health Diagnostics: Depending on the age of the mare, previous reproductive success, and findings on breeding soundness exam, further diagnostics may be appropriate.
   1. Culture: The uterine culture is a first line diagnostic tool to look for the presence of pathogenic bacteria in the uterus causing reduced fertility.
   2. Cytology: Uterine cytology can be coupled with culture to look for bacteria, fungal organisms, and inflammatory cells present in the uterus.
   3. Biopsy: A uterine biopsy is typically not a first line diagnostic tool, but rather something that is reached for after multiple lost pregnancies or a mare that fails to become pregnant. It is done by taking a small piece of the uterus and sending it off to be examined by a pathologist. Based on the readings by the pathologist, a score will be assigned looking at the prognosis for that mare to become pregnant and maintain pregnancy to term.
   4. Lavage: A sterile lavage of the uterus is a second-tier diagnostic tool that can be performed to collect cells and microorganisms when other diagnostics have low yield, yet the mare has continually failed to become pregnant.

I hope this newsletter has shed light on the value of having a breeding soundness exam performed prior to investing the time and resources into breeding the mare. As previously explained, the costs associated with getting the horse pregnant and how these expenses can increase quickly. Check out these additional resources to help prepare you for the equine breeding season.

https://vetmedbiosci.colostate.edu/erl/tag/breeding-basics/

https://equine-reproduction.com/articles/mares/mare-pre-breed

https://thehorse.com/182407/8-steps-for-breeding-your-mare/

https://equine-reproduction.com/articles/mares/vulva-caslick

https://thehorse.com/111556/before-you-breed-your-horse-costs-and-considerations/#:~:text=And%20the%20more%20times%20you,90%25%20of%20mares%20pregnant.%E2%80%9D

Written By: Dr. Gunner Edgell

Rocky River Large Animal Veterinary Clinic is here to serve you and your animals.