🐴 Reproduction in Obese Horses: How Metabolic Health Affects Fertility in 2025 ⚖️🧬

By Dr Duncan Houston BVSc

Breeding mares with obesity, Equine Metabolic Syndrome (EMS), or Equine Cushing’s Disease (PPID) poses unique challenges. In 2025, evidence continues to highlight how metabolic dysfunction and excess fat affect hormones, inflammation, and fertility. Here’s what you need to know. 🧠🐎

⚠️ Is It Safe to Breed an Obese Mare?

Breeding overweight mares—especially those with EMS or PPID—is generally not recommended without first addressing their underlying health conditions. ❌

Reasons include:

• 💥 Increased risk of laminitis and founder from added pregnancy weight
• 🔥 Chronic low-grade inflammation due to excess fat tissue
• 🧬 Hormonal disruptions that affect ovulation and cycle timing

🧪 How Metabolic Syndrome Affects Fertility

Equine Metabolic Syndrome (EMS) includes:

• ⚖️ Insulin resistance
• 📈 Obesity or abnormal fat deposition
• 🧠 Increased systemic inflammation

These conditions create an environment that disrupts normal reproductive hormone balance. Overweight mares often have:

• 📅 Longer cycles or skipped ovulation
• 🌡️ Persistent elevation of progesterone
• 🧫 Higher risk of uterine infections

🧠 What About Cushing’s Disease (PPID)?

Mares with PPID are more likely to have:

• 📉 Suppressed immune function
• 🧫 Uterine infections due to poor clearance and hormonal imbalances
• 📅 Continued cycling through winter—but with poor quality ovulations

These mares may appear to cycle year-round but are often less fertile overall. 🧬

🧹 The Role of Inflammation and Immunity

Excess fat acts as an endocrine organ, producing inflammatory mediators that affect:

• 🦠 Immune system function
• 🧠 Hormone feedback loops
• 🧬 Endometrial health

🧪 This creates a uterus more prone to infection—a major cause of infertility in mares. 🔬

📋 Should You Breed an Obese Mare?

Only after the following are addressed:

• 📉 Body condition reduced to a healthy level (BCS ~5/9)
• 🩺 EMS or PPID is medically managed and stable
• 🔍 Reproductive tract is clear of infection (culture + cytology)
• 📅 Hormones are cycling normally

Work closely with your veterinarian to run endocrine testing and develop a prep program before any attempt at breeding. ✅

📲 Ask A Vet for Metabolic Mare Breeding Plans

Have an overweight or Cushing’s-affected mare you’d like to breed? Visit AskAVet.com or use the Ask A Vet App to schedule testing, nutrition support, and pre-breeding exams. 📱🐴

Dr Duncan Houston and the team can help safely transition mares into a healthier state before planning pregnancy. 💬🧠

🏁 Final Thoughts

In 2025, breeding obese or metabolically challenged mares without preparation is risky for both mare and foal. With proper care, some mares may regain fertility—but it takes smart vet guidance, diet control, and time. 🐣🐎

Need a pre-breeding metabolic plan? Visit AskAVet.com to get started today 🐴⚖️