Vet Guide: What Is Grass Hay for Horses? 2025 🌾🐴

By Dr Duncan Houston, BVSc

When horse owners talk about feeding "grass hay," it may sound like a simple, one-size-fits-all forage. But the reality is far more complex. Grass hay can include dozens of grass species—each with its own nutritional profile, digestibility, and carbohydrate content. And for horses with special needs, such as insulin resistance or laminitis, those differences can make or break their health. 🧠🐎

In this 2025 veterinary guide, Dr Duncan Houston explains what grass hay really is, the most common types, how to identify quality, and why hay testing is a smart investment. 🌾📋

1. What Is Grass Hay? 🌿

Grass hay refers to hay made from various grass species harvested, dried, and baled for use as equine forage. It’s the foundation of most horse diets due to its high fiber content and low to moderate protein and energy. Grass hay supports digestive health and mimics the natural grazing behavior of horses. 🐴

2. Common Grass Species Used in Horse Hay 🧾

Grass hay may be a single species or a mix of several grasses. Some of the most common include:

• 🌱 Timothy: Highly palatable, low sugar, popular in northern U.S.
• 🌾 Orchard Grass: Soft texture, good protein, moderately high sugar
• 🌿 Bermuda Grass (Coastal): Common in southern U.S., lower sugar
• 🌾 Smooth Bromegrass: Cold tolerant, good digestibility
• 🌾 Tall Fescue: Durable but may contain endophytes—care needed in breeding stock
• 💠 Meadow Fescue / Kentucky Bluegrass: Often part of mixed hays
• 🌾 Ryegrass (Perennial & Italian): Soft texture, may be high in sugar
• 🌾 Wheat Hay: Often a by-product hay, higher NSC (sugars + starches)

Important: The specific mix of these grasses affects not only nutrition—but also suitability for different horses. 🔬

3. Why Hay Type Matters for Your Horse 🧠

Different grass types vary in:

• 🍽️ Palatability
• 🧬 Digestibility
• 📊 Non-structural carbohydrates (NSC)
• 💪 Crude protein and fiber content

💡 Example:

• 🐴 A horse with insulin resistance should avoid hay high in NSC (e.g., ryegrass or wheat hay)
• 🥕 A performance horse may benefit from more energy-dense hay like orchard grass

4. Why All Grass Hay Is Not Created Equal ⚠️

Many horse owners assume that all “grass hay” is interchangeable—but this isn’t true. Nutritional value depends on:

• 🌾 Species composition
• 🧓 Maturity at harvest
• 🌦️ Growing conditions (climate, soil, irrigation)
• 🧺 Storage methods

Older, more mature hay tends to be stemmier and lower in protein and digestibility. Younger, leafier hay is often higher in energy and nutrients—but also in sugars. 🧬

5. Key Nutrients in Grass Hay 📊

A typical forage analysis for grass hay includes:

Low NSC (<10%) is ideal for horses with Equine Metabolic Syndrome or laminitis risk. 📉

6. The Case for Hay Testing 🧪

Even hay from the same field can vary from one cutting to another. That’s why it’s essential to test:

• 🔬 Multiple samples from different bales
• 📦 Before purchasing large batches
• 🧾 Especially for horses with dietary restrictions

Cost: $30–$60 per sample at labs like Equi-Analytical—worth every penny for peace of mind. 💰

7. Reading a Forage Report: Quick Tips 📖

Look for these key values:

• 🧪 NSC <10% for metabolic horses
• 💪 Crude protein 8–12% for most adults
• 🌿 Leafy, green appearance = higher quality
• 👃 Smell should be fresh—not musty or moldy

Ask your vet to help interpret the analysis—especially if you're adjusting for a specific medical condition. 🩺

8. Comparing Bermuda Grass and Other Grass Hays 🆚

• 🌾 Bermuda grass: Lower in NSC, good digestibility, more common in the South
• 🌱 Orchard or Timothy: Higher in protein and NSC, popular in northern regions
• 🌾 Wheat hay: High NSC—avoid for EMS or laminitis-prone horses

Again, these are generalizations—always confirm with forage testing! 🔬

9. Summary Table: Grass Hays at a Glance 📋

10. Final Thoughts from Dr Duncan Houston 💬

Grass hay isn’t “just hay.” With so many species and such wide variation in nutrition, understanding what you’re feeding is essential—especially for horses with metabolic concerns or performance needs. Testing your hay and knowing your horse’s condition can ensure optimal health and prevent costly problems down the road. 🐴💡

For help selecting the right hay or interpreting a forage analysis, visit AskAVet.com or download the Ask A Vet app 📲 to connect with equine nutrition experts and veterinarians on demand.

— Dr Duncan Houston, BVSc