🐴 Carbohydrate Concentrations Affected by Grass Height for Grazing Horses: 2025 Guidelines for Laminitis Risk 🌾📉

By Dr Duncan Houston BVSc

Managing pasture access is crucial for horses prone to laminitis—especially those with insulin resistance or Equine Metabolic Syndrome (EMS). In 2025, new research continues to refine our understanding of how grass height affects carbohydrate content and metabolic risk. But don’t be fooled: shorter grass doesn’t always mean safer grazing. 🧠🐎

⚠️ Why Carbohydrates Matter

Laminitis in at-risk horses is often triggered by ingestion of non-structural carbohydrates (NSCs) in pasture grasses. NSCs include:

• 🍬 Simple sugars
• 🌾 Fructans (storage carbs produced via photosynthesis)
• 🍭 Starches

These carbohydrates raise blood glucose and insulin levels, which can damage the laminae in the hoof, causing painful and sometimes irreversible laminitis. 📉🦶

🔬 The Grass Height Study

Researchers at North Carolina State explored whether mowing pasture to shorter heights could reduce carbohydrate intake and affect metabolism. 🌿

Study Details:

• 🌾 Pasture type: Tall fescue
• 🌱 Two grass heights: 12 inches (tall), 6 inches (mowed)
• 🐴 Healthy horses rotated weekly between plots

📊 Key Findings:

• 🍽️ Horses consumed less total forage on shorter grass
• ⚖️ Some horses lost weight on the mowed plots
• 🔽 Carbohydrate intake was lower—but not eliminated

🚫 The Limitations

This study was helpful, but it’s critical to note:

• 🧬 Horses in the study were not insulin-resistant
• 🌾 Results only apply to fescue pasture, not all grass types
• 📉 Lower carb intake does not guarantee prevention of laminitis in high-risk horses

Even mowed grass can still contain high levels of fructans depending on stress, season, and photosynthesis activity. ❄️🌤️

🔍 Grass Physiology Matters

Fructans and other NSCs are produced via photosynthesis and stored in the stem and base of the plant—areas more accessible when grass is short or overgrazed. This means:

• 📏 Mowing can increase access to higher carb portions of the plant
• ⚠️ Horses may still ingest dangerous sugar loads despite reduced grass mass

🧠 Should You Mow Pasture for IR Horses?

If you’re trying to reduce carbohydrate risk, mowing is not a standalone solution for horses with insulin resistance. Instead, combine with:

• 🐴 Grazing muzzles
• 🔒 Limited turnout hours (early morning only)
• 🌾 Pasture rotation and rest periods
• 📦 Dry lots with hay testing under 10% NSC

📲 Ask A Vet for Customized Pasture Plans

Unsure if your pasture is safe? Visit AskAVet.com or use the Ask A Vet App for pasture evaluation, forage testing, and grazing strategies tailored to insulin-resistant horses. 📱🐴

Dr Duncan Houston and the team can help with seasonal turnout guidance, safe mowing techniques, and metabolic horse monitoring. 💬🧠

🏁 Final Thoughts

In 2025, managing laminitis risk in horses is about much more than grass height. While mowing can reduce forage mass, it doesn’t necessarily lower sugar content enough to protect at-risk horses. 🐴🌾

Need help designing a safe grazing plan? Visit AskAVet.com for expert support 🐎📉