The Caslick’s Procedure in Pregnant Mares: Purpose, Process, and Aftercare

The Caslick’s procedure, also known as a Caslick’s vulvoplasty, is one of the most common reproductive surgeries performed on mares. It involves partially closing the upper portion of the vulva to prevent air and bacterial contamination from entering the reproductive tract.

This simple yet highly effective procedure is especially important for broodmares that have poor vulvar conformation or a history of reproductive infections, abortion, or placentitis. For pregnant mares, a Caslick’s can make the difference between a successful foaling and a lost pregnancy.

What Is the Caslick’s Procedure

The Caslick’s procedure was developed by Dr. Emil Caslick in the 1930s as a method to improve reproductive success in mares with poor vulvar seal or conformation defects. It involves suturing together the upper two-thirds of the vulvar lips, leaving an opening at the bottom to allow urination.

By closing most of the vulva, the Caslick’s creates a physical barrier that protects the uterus and vagina from bacteria, dust, manure, and air being sucked into the reproductive tract during movement or exercise, a condition known as pneumovagina.

Why It’s Done

A healthy, well-conformed vulva forms a natural seal that keeps the reproductive tract clean and prevents infection. However, in some mares, this barrier is compromised due to age, injury, or poor perineal structure.

Common Reasons for Performing a Caslick’s:

• Poor vulvar conformation (the vulva tilts forward or sits below the pelvic brim)
• Older mares with weakened perineal muscles and stretched tissues
• Mares that have had multiple foals or traumatic births
• Thin or underweight mares, where fat loss reduces vulvar support
• Mares that “windsuck” air into the vagina during movement
• Recurrent uterine infections or placentitis in previous pregnancies
• Prevention of ascending bacterial infection in pregnant mares

In breeding mares, a Caslick’s procedure is often performed after insemination or natural cover and once pregnancy is confirmed. It helps protect the developing foal from infection throughout gestation.

Timing of the Caslick’s Procedure

The Caslick’s is typically performed after breeding but before mid-pregnancy, once the veterinarian has confirmed conception via ultrasound (usually around 14–18 days post-ovulation). Performing the surgery too early may interfere with drainage after insemination, while performing it too late may pose risks if the mare has already developed uterine contamination.

In some cases, mares with chronic infections or poor conformation may have a Caslick’s even before breeding, which is then opened temporarily for insemination and closed again afterward.

The Procedure: Step by Step

The Caslick’s procedure is quick, safe, and usually performed under standing sedation and local anaesthesia. It takes about 10–20 minutes.

Step 1: Preparation

The mare is restrained in stocks or a safe area. The tail is wrapped, and the perineal area is cleaned thoroughly with antiseptic solution to minimise contamination.

Step 2: Anaesthesia

A local anaesthetic is injected along the edges of the vulvar lips. Sedation may also be administered to keep the mare calm.

Step 3: Removal of a Thin Strip of Tissue

A small strip (2–3 mm wide) of the mucous membrane from the inner edge of each vulvar lip is carefully removed using a scalpel or surgical scissors. This creates a clean surface that will heal together when sutured.

Step 4: Suturing

The two sides of the vulva are brought together and closed using fine, non-absorbable sutures, usually in a simple continuous or interrupted pattern. The lower one-third of the vulva remains open to allow normal urination and drainage.

Step 5: Aftercare

An antibiotic ointment is applied to the incision line, and the mare is monitored for swelling, irritation, or discharge.

The stitches remain in place for the duration of the pregnancy and are removed shortly before foaling.

Aftercare and Monitoring

The incision site should be checked daily for signs of swelling, discharge, or irritation. Most mares heal within 10–14 days with minimal complications.

Post-Surgery Care:

• Keep the mare in a clean environment to prevent contamination.
• Avoid breeding or vaginal examination while the Caslick’s is in place.
• Monitor for signs of urination difficulty or discomfort.
• Apply an antibiotic ointment to the incision if recommended by the veterinarian.

Mares can resume normal turnout and exercise once healing is complete.

Opening the Caslick’s Before Foaling

One of the most important steps in managing a pregnant mare with a Caslick’s is reopening the vulva before foaling. If the Caslick’s remains closed, the mare could tear the vulva severely while giving birth, resulting in permanent damage and increased risk of future infections.

Timing

The Caslick’s is usually opened 2 to 4 weeks before the expected foaling date or when the mare begins to show signs of impending labour (udder filling, relaxation of pelvic ligaments, etc.).

The reopening is a simple procedure performed by a veterinarian using local anaesthesia. The scar line is cut along the previous suture to restore the natural vulvar opening.

If the Caslick’s Is Not Removed

Failure to open the Caslick’s can lead to:

• Severe tearing of the vulva and perineum during foaling
• Pain, bleeding, and scarring
• Increased risk of infection postpartum
• Complications in future breeding

Therefore, scheduling the reopening is an essential part of pre-foaling management.

Risks and Complications

The Caslick’s procedure is low-risk, but complications can occur if not managed properly.

Possible Complications:

• Swelling or infection at the incision site
• Difficulty urinating (if too much of the vulva is closed)
• Accidental reopening if the mare strains or kicks
• Scarring from improper reopening before foaling

With proper care and timing, these issues are rare and easily managed.

Benefits of the Caslick’s Procedure

When performed correctly, the Caslick’s procedure provides several key advantages, particularly for broodmares at risk of reproductive infection.

Key Benefits:

• Reduces risk of ascending bacterial infection
• Prevents “windsucking” and contamination of the vagina
• Protects against placentitis and abortion
• Improves reproductive success and foal survival rates
• Simple, quick, and inexpensive procedure with minimal recovery time

Prevention and Good Management

While the Caslick’s procedure is an effective solution for at-risk mares, it should be complemented by good breeding and management practices.

• Maintain proper body condition to support perineal tone.
• Provide regular veterinary examinations during pregnancy.
• Ensure breeding hygiene (clean equipment and hands).
• Avoid unnecessary vaginal examinations during gestation.
• Keep mares in clean, dry paddocks to reduce bacterial exposure.

Conclusion

The Caslick’s procedure is a simple but invaluable tool in equine reproductive medicine. For mares with poor vulvar conformation, a history of infections, or prior abortions, it offers an effective way to safeguard the uterus and developing foal from contamination.

When performed and managed properly, closed after breeding and reopened before foaling, it significantly improves pregnancy outcomes and reduces the risk of complications such as placentitis or dystocia.

Every breeder with mares prone to reproductive challenges should discuss the Caslick’s procedure with their veterinarian as part of a comprehensive breeding and foaling management plan.