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One of the most crucial components of equine reproductive success is conducting a thorough mare breeding soundness exam. This comprehensive evaluation helps determine whether a mare is physically and reproductively capable of conceiving, carrying, and delivering a healthy foal.
Whether you’re preparing a maiden mare for her first pregnancy or rebreeding a seasoned broodmare, the mare breeding soundness exam is the gold standard for establishing her suitability for breeding. In this article, we’ll walk through the steps involved in a mare breeding soundness exam. We will reference established practices from veterinary experts that contribute to reliable and successful reproductive outcomes.
What Is a Mare Breeding Soundness Exam?
A mare breeding soundness exam (BSE) is a systematic evaluation performed by a veterinarian with reproductive expertise. Its goal is to determine if a mare is anatomically and physiologically fit for breeding. This includes assessing her general health, breeding history, and reproductive anatomy.
Both the Colorado State University Equine Reproduction Laboratory and Mad Barn emphasize that these exams are valuable tools in equine breeding programs. They allow for early identification of issues that could reduce fertility or jeopardize pregnancy.
When Should a Mare Breeding Soundness Exam Be Performed?
A mare breeding soundness exam should be completed at the beginning of each breeding season, to ensure the mare is fit for breeding. The exam can also be helpful in the following scenarios:
- Before breeding a (maiden) mare for the first time; the exam can be especially helpful for older maidens
- After a failed breeding or a pregnancy loss
- Before committing a mare to assisted reproductive techniques such as artificial insemination and embryo transfer; to assess the mare’s suitability for these techniques
- Before purchasing a mare as a broodmare prospect; as part of a pre-purchase examination
- When preparing an experienced older mare for the breeding season; fertility can begin to decrease between 10 and 15 years
- After a successful healthy pregnancy/foaling, to check the reproductive tract for any inflammation, fluid, or infection before breeding again
- After the breeding season when a mare has proved barren
An ideal time to perform the exam can be during the transitional phase into the breeding season. This timing allows for any issues to be addressed before the breeding schedule begins.
Core Steps of a Mare Breeding Soundness Exam
Below are key components of a mare breeding soundness exam.
1. Comprehensive Medical and Reproductive History
The first step in the mare breeding soundness exam involves gathering a thorough medical and reproductive history. This can include:
- Mare’s age and breed
- Diet and nutrition
- Vaccination status
- Health issues, injuries, and surgeries
- Details of estrous cycles
- Details of breeding history such as age at first breeding, number of attempts required to produce pregnancies, breeding methods used, and number of breedings in the previous season
- Details of pregnancy history such as date of most recent foaling, issues carrying and delivering foals, ability to produce milk and to mother foals, and any pregnancy losses
A detailed history provides context for interpreting physical and reproductive findings later in the exam.
2. General Physical Examination
Before focusing on reproductive structures, the vet performs a complete physical exam. This can include:
- Evaluating body condition; broodmares can be slightly heavier than performance horses, but they should not be overweight
- Checking respiratory and cardiac function
- Examining musculoskeletal soundness
- Examining the udder for overall soundness and lactation potential
- Looking for any systemic illnesses
- Looking for any hereditary conditions that may be problematic for offspring and would preclude the mare from breeding
A healthy mare is more likely to conceive, carry, and foal successfully. The physical exam helps identify any underlying issues that could interfere with reproductive performance.
3. External Reproductive Examination
The next step of the mare breeding soundness exam is inspection of the external reproductive anatomy. This can include:
- Conformation of the vulva (Does it form a tight “seal” so air, feces, and other material do not enter the reproductive tract and potentially cause infection?)
- Positional relation of the vulva to the pelvis
- Presence of injury or discharge
If the conformation is problematic and the “seal” is not sufficient, a veterinarian can do a Caslick’s procedure. This involves suturing the top two-thirds of the vulva closed. The procedure can be done specifically after breeding to help decrease the chances of infection and pregnancy loss. In this case, sutures can be removed before foaling. For mares not yet pregnant, sutures can be removed before natural breeding and the area re-sutured after breeding. Sutures may be able to remain in place for artificial insemination.
4. Internal Reproductive Tract Palpation and Ultrasound
After the external exam, the veterinarian palpates the internal reproductive tract through the rectal wall (transrectally). This includes:
- Cervix
- Uterus
- Ovaries
Rectal palpation provides tactile feedback about the size, shape, and tone of the anatomy. Transrectal ultrasound is used to detect:
- Follicular activity on the ovaries
- Irregular ovarian formations
- Uterine fluid
- Uterine cysts
Ultrasound helps identify any abnormalities that may compromise fertility.
5. Vaginal Examination with Speculum (Tube)
Another component of the mare breeding soundness exam involves vaginal examination using a speculum (tube). A veterinarian may prefer to perform this part of the exam after the Uterine Culture and Cytology. The goal is to visually inspect:
- Cervical external appearance (e.g., color, inflammation); This stage of the process may also include a digital/palpation exam of the cervix to check for tears, thin areas, or other abnormalities
- Discharge from the cervix that could indicate a uterine infection
- Urine pooling in front of the cervix
- Vaginal wall condition (e.g., inflammation, lacerations, scarring)
- Trauma from natural breeding or from foaling
6. Uterine Culture and Cytology
Uterine health is critical to a successful pregnancy. A sterile appliance with guard (a swab for culture, a swab or brush for cytology) can be used to collect samples. Also, low-volume lavage can be used.
- Uterine Culture – to detect bacterial growth
- Uterine Cytology – to check (under microscope) for the presence of bacteria or inflammatory cells (neutrophils); Advantages of endometrial cytology include relative ease of sample collection, quick results, and cost-effectiveness
Together, these tests help detect endometritis or other infection and inflammation that could prevent pregnancy. Endometritis is an inflammation of the uterine lining caused by bacterial infection, fungal infection, and overactive inflammatory response to semen and other foreign material. It is believed to be a major cause of reduced fertility in mares.
7. Uterine Biopsy
For mares with continuing reproductive challenges, a uterine biopsy may be performed. This involves:
- Taking a small sample of endometrial tissue (from the base of one of the uterine horns)
- Submitting the sample for analysis to assess condition of the uterine tissue and presence of inflammation “markers”
The biopsy assesses tissue structure, presence of inflammation, presence of fibrosis, and overall tissue health. Mares are graded (I, IIA, IIB, III) according to their likelihood of carrying a foal to term. This is one of the most effective tools in a mare breeding soundness exam to indicate reproductive viability.
8. Further Testing (As Needed)
If regular procedures in the mare breeding soundness exam do not identity the cause(s) of subfertility in a mare, other examinations may be recommended, including hormone analysis, chromosome analysis, and videoendoscopy (hysteroscopy).
Additional Considerations in a Mare Breeding Soundness Exam
The exam does not end with the checklist. Contextual interpretation of all data is vital. For instance, “Category IIB or III mares may still be able to produce embryos that other mares can carry to term through embryo transfer.” (Mad Barn)
Mares are individuals, and successful breeding outcomes can depend on personalized strategies developed from a thorough mare breeding soundness exam.
The Importance of Timing and Planning
The timing of the exam is essential to ensure the mare is ready for the breeding season. Performing a mare breeding soundness exam early allows for treatment plans, recovery time, and scheduling of natural breeding or insemination.
At The Farm at Brookside, we believe that investing in a mare breeding soundness exam can help make successful breedings, healthy pregnancies, and thriving foals possible.
The Role of the Breeding Team
No matter how thorough the exam, it must be supported by a skilled breeding team. From monitoring ovulation cycles to managing insemination and pregnancy care, our experienced professionals work to ensure every mare receives optimal care.
We collaborate closely with owners to create a tailored plan based on each mare’s unique needs.
Summary: Why the Mare Breeding Soundness Exam Matters
The mare breeding soundness exam can be a critical step in a successful breeding program. It offers a comprehensive view of the mare’s reproductive health and can help identify problems before they lead to failed breeding or loss of pregnancy.
At The Farm at Brookside, we take pride in offering quality care rooted in proven science. A mare breeding soundness exam can be a solid first step toward a healthy foal.
For more information or to schedule an appointment with our team, visit thefarmatbrookside.com. Let us help your mare begin her journey toward successful motherhood with a comprehensive mare breeding soundness exam.
Sources:
Artman, Jessica (Author), Kerley, Brittany (Reviewer), Rowe, Fran (Veterinary Reviewer). “Breeding Soundness Exams for Mares: Assessing Reproductive Health [8-Step Guide].” madbarn.com. 1 May 2025 (Updated), 23 November 2023 (Published). https://madbarn.com/breeding-soundness-exam-for-mares/?srsltid=AfmBOoppbrPhYNUWeD8amI2kpZGXT47Z-rnakiCiD8zEfKvGGg2Fq-2f.
Equine Reproduction Laboratory, Colorado State University. “Mare Reproductive Evaluation.” vetmedbiosci.colostate.edu. 15 November 2022. https://vetmedbiosci.colostate.edu/erl/2022/11/15/mare-reproductive-evaluation/.
Johnson, Aime K. Equine Theriogenology Service, Auburn University. “Back to the Basics: Importance and Interpretation of a Breeding Soundness Exam in the Mare.” vetmed.auburn.edu. Accessed 5 June 2025. https://www.vetmed.auburn.edu/wp-content/uploads/2018/09/Mare-BSE-Techniques.pdf.
