Green Prairie Animal Hospital · Large Animal & Equine Care · Mason County, IL
Breeding season is coming and you’ve got decisions to make. Which mares are ready. Which ones need work before they’ll settle. Whether to use live cover, artificial insemination, or shipped cooled semen. And whether the stallion you’re planning to use is actually going to get the job done.
Getting a mare in foal is not complicated when everything is working right. The problem is you don’t always know what’s working right until you look. Here’s what equine reproductive services at Green Prairie Animal Hospital’s San Jose clinic involve — and what Mason County horse owners and breeders need to know going into breeding season.
Breeding Soundness Exams Set the Foundation
Before you breed a mare, you want to know she’s capable of conceiving and carrying a foal to term. A breeding soundness exam — sometimes called a pre-breeding exam — evaluates the mare’s reproductive tract and identifies anything that could interfere with conception or pregnancy.
The exam includes a rectal palpation and transrectal ultrasound — using an ultrasound probe placed rectally to visualize the ovaries and uterus directly. Ultrasound is the most important diagnostic tool in equine reproduction. It shows follicle development on the ovaries — follicles being the fluid-filled structures that contain the egg and grow in size as ovulation approaches — uterine tone and texture, the presence of fluid in the uterus, and any structural abnormalities that affect breeding decisions.
A uterine culture and cytology — a swab of the uterine lining examined under a microscope — checks for bacterial infection and inflammation. Mares with subclinical endometritis — low-grade uterine inflammation that produces no obvious external signs — have significantly reduced conception rates. Identifying and treating it before breeding rather than after several failed cycles saves time and money.
Perineal conformation — the physical structure of the mare’s vulva and surrounding tissue — is also evaluated. Mares with poor perineal conformation draw air and fecal contamination into the reproductive tract, leading to chronic infection. Caslick’s procedure — a minor surgical correction where the upper portion of the vulva is sutured closed to create a better seal — resolves this and is one of the most commonly performed and most effective procedures in equine reproduction.
Timing Breeding to Ovulation Is Everything
A mare’s egg is viable for a very short window after ovulation — roughly eight to twelve hours. Sperm viability in the reproductive tract extends longer, but the practical reality is that breeding too early or too late in the cycle produces dramatically lower conception rates regardless of how healthy the mare and stallion are.
Mares are seasonally polyestrous — meaning they cycle during the longer days of spring, summer, and early fall, and are largely reproductively inactive during winter. The transition into the breeding season in late winter and early spring produces irregular, prolonged cycles that can be difficult to time. Many breeding failures in early spring are timing failures, not fertility failures.
Monitoring follicle development with serial ultrasound — checking the mare every one to two days as a dominant follicle grows toward ovulation — is the most reliable way to time breeding accurately. Follicles typically ovulate between 35 and 55 millimeters in diameter, though this varies between individual mares. Knowing a specific mare’s normal ovulation pattern makes timing more predictable with each subsequent cycle.
Ovulation can be induced pharmacologically — using hormones like hCG (human chorionic gonadotropin) or deslorelin to trigger ovulation within a predictable window once a follicle has reached appropriate size. This is particularly useful when coordinating with shipped cooled semen, which has a limited viable window after collection and shipping.
Live Cover, Artificial Insemination, and Shipped Semen
The breeding method you choose affects how the reproductive program is managed and what veterinary involvement is required.
Live cover — natural mating — is straightforward from a management standpoint but limits your stallion options to horses within hauling distance and carries inherent risks for both animals during breeding. It’s the most common method for operations using a stallion on the same property.
Artificial insemination with fresh or fresh-cooled semen is the most widely used method in performance horse breeding. Semen is collected from the stallion, evaluated for motility and morphology — the percentage of sperm moving correctly and the percentage with normal shape — extended in a protective medium, and either used immediately or shipped cooled overnight to arrive at the mare’s location. Shipped cooled semen typically remains viable for 24 to 48 hours after collection — which is why accurate ovulation timing is critical. Breeding too early or receiving semen after viability is lost produces the same result: an open mare.
Frozen semen extends the options further — frozen semen from stallions anywhere in the world, including deceased stallions, can be used years after collection. The tradeoff is lower conception rates per cycle compared to fresh or cooled semen, and the requirement for precise insemination timing, typically within hours of ovulation. Frozen semen breeding requires a veterinarian on-site at insemination time and close ultrasound monitoring to get the timing right.
Your veterinarian can help you evaluate which method makes the most sense for your mares, your stallion options, and your operation’s goals.
Stallion Evaluation — Know What You’re Working With
If you stand a stallion or are evaluating a new one for your breeding program, a stallion breeding soundness exam gives you objective information about what you’re actually working with before the season starts.
Semen evaluation includes total sperm count per ejaculate, progressive motility — the percentage of sperm moving forward in a normal pattern — morphology, and concentration. A stallion with low motility or high morphological abnormality rates will produce disappointing conception rates regardless of his physical appearance, pedigree, or show record. These numbers tell you what the physical exam cannot.
Libido and breeding behavior are also assessed. A stallion that is slow to breed or shows inconsistent interest creates logistical problems in a busy breeding season and may require management adjustments.
Semen longevity testing — evaluating how well a stallion’s semen maintains quality after cooling and shipping — is essential before committing to a shipped semen program. Some stallions that look excellent on fresh evaluation ship poorly. Knowing this before you’ve sent semen across the country to a mare at the point of ovulation prevents expensive and frustrating failures.
Pregnancy Confirmation and Early Pregnancy Monitoring
Breeding is the beginning of the process, not the end. Pregnancy confirmation should happen at 14 to 16 days post-ovulation — early enough to detect twin embryos, which must be managed immediately in mares.
Mares carry single foals. Twin pregnancies in horses almost universally result in abortion of both fetuses, often late in gestation after significant investment. Early ultrasound detection of twins allows manual reduction — collapsing one embryonic vesicle while the other is left to develop normally — a straightforward procedure at 14 to 16 days that becomes progressively more difficult and less successful as pregnancy advances.
Follow-up ultrasound at 28 days confirms fetal heartbeat and continued development. A pregnancy that was confirmed at 16 days is not guaranteed to continue — early embryonic loss is common enough in mares that a single early check is not sufficient monitoring for a valuable mare or a breeding investment worth protecting.
Progesterone supplementation — providing the hormone that maintains pregnancy in the early months — is recommended for mares with a history of early pregnancy loss, older mares, and mares that abort under stress. Your veterinarian will evaluate whether supplementation is appropriate for your mare’s specific situation.
Green Prairie Animal Hospital Serves Mason County Breeders
For horse breeders and owners in Mason County and across central Illinois, Green Prairie Animal Hospital’s San Jose location handles the full range of equine reproductive services — mare breeding soundness exams, serial ultrasound monitoring, ovulation induction, artificial insemination with fresh and cooled semen, frozen semen insemination, stallion evaluation, pregnancy confirmation, and twin reduction.
The San Jose team does farm calls throughout Mason County — reproductive work is performed on your property, which means no hauling mares during a time-sensitive breeding window. When ovulation timing requires monitoring every 24 to 48 hours, having a veterinarian who comes to you makes the logistics manageable.
As an AAHA-accredited clinic, the protocols behind every reproductive exam and every procedure meet the highest standards in veterinary medicine — current techniques, properly maintained equipment, and a team that stays current on equine reproductive medicine.
Call San Jose for Equine Breeding Services in Central Illinois
Green Prairie Animal Hospital’s San Jose location is our large animal and equine center for Mason County and central Illinois. Our team handles horses, cattle, and livestock — and we do farm calls.
