🐴 Complications Using Glass Balls to Suppress a Mare’s Estrus: Safer Options in 2025 💊🚫

By Dr Duncan Houston BVSc

For mares that become difficult or unrideable during heat, estrus suppression is often necessary for comfort, focus, and safety. While hormonal therapy is the standard, some owners have explored alternatives like intrauterine glass balls. In 2025, we now better understand the complications of this technique—and the importance of choosing safer options. 🧠🐎

💡 Why Suppress Estrus in Mares?

Hormonal cycling in mares can cause:

• 🚫 Refusal to work under saddle
• 😠 Behavioral changes, irritability
• 🐎 Performance decline

Some mares are affected so severely that they cannot be shown or trained while in heat. 🔁

🔵 The Glass Ball Method: How It Works

The technique involves inserting a sterile glass ball or marble into the uterus after ovulation. It’s thought to simulate pregnancy, suppressing estrus. 🧬

Published research and field use showed about 50% effectiveness. For some time, this was a popular “low-maintenance” alternative to daily hormones. 🧠

⚠️ Reported Complications

Recent case reports have raised concerns:

• 🦠 A mare developed a severe uterine infection after ball insertion
• 💥 In another case, two glass balls shattered inside the uterus, embedding shards in uterine tissue

The cause of breakage is unclear, but damage was significant. Once embedded, glass is nearly impossible to remove without surgical intervention. 🚨

Why This Matters:

• 🧪 Glass fragments cause ongoing inflammation and scarring
• 📉 May lead to permanent infertility
• ⚠️ High risk of endometritis or uterine abscesses

Given these risks, the method is no longer recommended for most mares. ❌

✅ Safer Alternatives in 2025

💉 1. Daily Progestin (e.g., Altrenogest/Regumate)

• 🔁 Suppresses ovulation and estrus behavior
• 💊 Must be given daily—gloves required (absorbs through skin)
• 📉 Expensive but effective

💉 2. Long-Acting Hormone Injections

• 🧪 Compounded progestins that last 2–3 weeks
• 📆 Ideal for show season scheduling

💉 3. Oxytocin Protocol

• 🧠 Administered for 2–3 days after ovulation
• 📉 Suppresses return to heat by prolonging the luteal phase
• ✅ Hormone-free and safe when timed correctly

This method is particularly appealing for mares with sensitivities to hormone therapy. 💡

🩺 Choosing the Right Method

Factors to consider:

• 📆 Length of suppression needed
• 🐴 Severity of estrus behavior
• 🧬 Mare’s health history and sensitivity
• 💵 Budget and practicality

📲 Ask A Vet for Estrus Suppression Planning

Need help managing estrus in a performance or breeding mare? Visit AskAVet.com or use the Ask A Vet App for tailored protocols and safe suppression options. 📱🐴

Dr Duncan Houston and the team can guide you through medication options, dosage schedules, and non-hormonal alternatives like oxytocin. 💬🧠

🏁 Final Thoughts

In 2025, better solutions exist than glass balls for estrus suppression. With long-acting progestins and oxytocin protocols available, you can help your mare feel and perform better—without risking her uterus or future fertility. 💉🐎

Looking for safe estrus control? Visit AskAVet.com and support your mare’s performance 🐴💊