🐴 Neonatal Isoerythrolysis in Foals: Prevention & Emergency Care for 2025 🩸🍼

By Dr Duncan Houston BVSc

Neonatal isoerythrolysis (NI) may sound complex—but the concept is simple: the foal’s red blood cells are destroyed by antibodies from the mare. In 2025, timely prevention and awareness are vital to stop this dangerous condition before it becomes fatal. 🧠🐎

🧬 What Is Neonatal Isoerythrolysis?

Neonatal isoerythrolysis (NI) is a disease that causes a foal’s immune system to attack its own red blood cells. But these antibodies don’t come from the foal—they come from the mare’s colostrum. 🍼

How It Happens:

1. 🧪 The mare has antibodies against red blood cell antigens the foal inherited from the sire
2. 🍼 These antibodies are passed through the colostrum the foal drinks shortly after birth
3. 💥 The antibodies attack and destroy the foal’s red blood cells, causing anemia

⚠️ Clinical Signs of NI

Symptoms often appear within 1–4 days after birth and include:

• 😴 Weakness or lethargy
• 🥱 Poor nursing
• 🌕 Pale or yellow mucous membranes (icterus)
• 💓 Increased heart and respiratory rate

These signs are caused by the loss of oxygen-carrying red blood cells. In severe cases, NI is life-threatening. 🚨

🧪 Diagnosing NI

If NI is suspected, your vet will:

• 🩸 Perform a Complete Blood Count (CBC) to confirm anemia
• 🔬 Conduct a Coombs test to detect antibodies on the foal’s red cells

💉 Treatment Options

If NI is diagnosed early:

• 🚫 Prevent the foal from nursing if under 24 hours old
• 🥣 Feed alternative colostrum or milk replacer

If the foal is already symptomatic:

• 💉 May require a blood transfusion
• 🧽 Blood must be wash-filtered from the mare or sourced from a compatible donor

Supportive care and constant monitoring are essential for survival. 🩺

✅ Prevention Is the Best Treatment

If your mare has previously foaled a case of NI—or if you’re unsure of blood type compatibility—take these steps:

Before Breeding:

• 🧬 Test mare and stallion blood types for compatibility
• 🩸 Submit blood to UC Davis or a specialized lab to detect risk

Before Foaling:

• 🔬 Screen the pregnant mare’s blood for anti-RBC antibodies

At Birth:

• 📅 Have a foaling plan in place
• 🚫 Prevent the foal from nursing until colostrum is tested
• 🥣 Use colostrum bank or milk replacer if necessary

📲 Ask A Vet for Neonatal Emergency Planning

If you have a history of NI foals or a mare with incompatible blood type, visit AskAVet.com or use the Ask A Vet App to create a birth plan, access colostrum alternatives, and prepare for safe delivery. 📱🐴

Dr Duncan Houston and the team can walk you through step-by-step NI prevention and response. 💬🧠

🏁 Final Thoughts

Neonatal isoerythrolysis is preventable—but only with knowledge, testing, and a proactive plan. In 2025, you can protect foals from anemia, weakness, and transfusion emergencies by working closely with your vet before breeding and foaling. 🐣🐎

Concerned about NI in your mare? Visit AskAVet.com and prepare ahead 🐴🩸