🐴 Antibiotic Use in Horse Reproduction: Treating Uterine Infections Responsibly in 2025 💊🧬

By Dr Duncan Houston BVSc

One of the leading causes of infertility in mares is a uterine infection. These infections can disrupt conception, cause early embryonic loss, and lead to chronic reproductive issues. However, not all uterine infections are created equal, and not every positive culture means antibiotics are needed. In 2025, we're practicing more targeted, evidence-based treatment to improve conception rates while minimizing antibiotic overuse. 🧠🐎

🔍 Diagnosing a True Uterine Infection

Many mares are treated with antibiotics based on bacterial cultures alone. But this isn’t always appropriate. The presence of a bacterium doesn’t necessarily mean there’s a true infection. 🧫

✅ The gold standard for diagnosis includes:

• 🧬 A positive uterine culture (bacteria identified)
• 🔬 Cytology: Microscopic evidence of inflammation or infection (e.g., white blood cells)

If cytology shows no inflammation, the mare may simply be a carrier of a non-pathogenic organism. Treating unnecessarily may cause more harm than good. 🧪

🧴 Uterine Infusion of Antibiotics

The traditional treatment for uterine infections involves infusing antibiotics directly into the uterus. While effective, this method has limitations: 🛑

• 🧼 Uterine secretions or pus can inactivate the antibiotic
• 🧽 It’s essential to flush the uterus first with sterile saline or lactated Ringer’s solution
• 📆 Most mares need 3–7 days of infusion for best results

Infusions are labor-intensive and carry a small risk of introducing contaminants if not performed correctly. 📉

💉 Systemic Antibiotic Treatment

Recent studies show that systemic antibiotics—administered via injection or orally—can reach effective concentrations in the uterus. This approach offers several advantages: ✅

• 🛡️ Less invasive: No need to enter the uterus daily
• 🔁 Reduced contamination risk
• 📦 Easier for long-term or field treatment

However, systemic antibiotics may require longer treatment durations and only select drugs can reach therapeutic levels in the reproductive tract. 💊

🧪 Choosing the Right Antibiotic

Your vet will usually select antibiotics based on:

• 🧬 Culture and sensitivity results
• 📍 Location of infection (uterine vs systemic)
• 📉 Severity of clinical signs

Commonly used options for systemic use include:

• 💉 Trimethoprim-sulfa
• 💉 Oxytetracycline
• 💉 Ceftiofur (with caution due to resistance)

📉 When Antibiotics Alone Won’t Work

Some mares have anatomical abnormalities (e.g., poor vulvar conformation, urine pooling) that allow bacteria to enter the uterus easily. In these cases, infections will keep returning unless the anatomical issue is surgically corrected. 🏥

Treatment might include:

• ✂️ Caslick’s procedure (partial vulvar closure)
• 🧼 Uterine lavage and debridement

No amount of antibiotics will permanently solve the problem if the uterine barrier remains compromised. 🛑

🔁 Repeat Breeders and Subclinical Infections

Some mares are repeat breeders—failing to conceive after several breedings. In these mares, subtle or subclinical infections may go undetected without proper diagnostic work. Signs include:

• 📉 Embryo loss after day 15
• 🩸 Persistent fluid in the uterus post-breeding
• 🔍 Mild white blood cell presence on cytology

Thorough diagnostics and targeted treatment are the best tools for giving these mares another chance. 💡

📲 Ask A Vet for Repro Planning & Infections

If your mare has failed to conceive or has been treated for uterine infection without results, get a second opinion at AskAVet.com or through the Ask A Vet App. 📱🐴

Dr Duncan Houston and the team can review cytology, cultures, and help you plan a more targeted approach to uterine therapy. 🧬💬

🏁 Final Thoughts

In 2025, responsible antibiotic use in reproduction is more important than ever. Not every positive culture warrants treatment—and when antibiotics are needed, flushing, testing, and targeted delivery methods can help protect fertility and limit resistance. 🧠❤️

Need expert help treating uterine infections? Visit AskAVet.com to build a safe, effective breeding plan 🐎💊