Can You Feed Your Horse Alfalfa? What To Know

Alfalfa is one of the most debated forages in the horse world — and for good reason. While it can support muscle, milk, and growth, it’s also been linked to laminitis, hoof sensitivity, kidney stress, and behavioral reactivity in sensitive horses.

This guide will walk you through the nutritional science, risks, benefits, and best practices of feeding alfalfa — so you can make the right decision for your horse, whether they’re a high-level athlete, an easy keeper, or something in between.

What Is Alfalfa and Why Is It Fed to Horses?

Alfalfa is a legume hay, rich in protein, calcium, and digestible energy. It has long been used in equine diets, particularly for:

• Performance horses
• Lactating or pregnant mares
• Foals and young growing horses
• Hard keepers or seniors with dental issues

Its high nutrient density makes it especially useful for horses with elevated nutritional requirements. However, feeding too much to low-need horses (like idle geldings) may lead to unwanted weight gain and behavior issues from insufficient gut fill.

Alfalfa has a higher acid-buffering capacity than grass hay, which can help protect against gastric ulcers when fed before exercise.

Nutritional Breakdown of Alfalfa Hay

Alfalfa hay’s nutritional content can vary based on soil, climate, and harvest conditions — the only way to know exactly what’s in it is to get it tested.

Here’s a typical nutritional profile of good-quality alfalfa hay:

Alfalfa offers excellent nutrition but easily exceeds the requirements of most mature horses at maintenance or light work.

Alfalfa’s nutritional value shifts dramatically as the plant matures. Early in its growth, the leaf-to-stem ratio is high, meaning more protein-rich leaves and fewer fibrous stems. The leaves carry most of the protein, while the stems are the main source of fiber — and that fiber becomes tougher and less digestible with age.

As alfalfa matures, crude protein levels decline, and some of that protein becomes bound by lignin, making it unavailable to the horse. At the same time, fiber content increases — both neutral detergent fiber (NDF) and acid detergent fiber (ADF) go up, especially in the stems. This reduces digestibility and palatability.

Here’s how the plant progresses:

• In the early vegetative stage (around 30 cm tall), alfalfa has very high protein (around 24–25%) and relatively low fiber.
• By the later vegetative stage (around 60 cm tall), protein starts to dip slightly, and fiber begins to climb.
• At the bud stage, protein drops further, and fiber increases significantly.
• Once flowers appear, the protein is lower still (around 17–18%) and the fiber peaks.

The best time for harvesting?
Between the late vegetative and early flowering stages. That’s when you’ll get the best balance of protein, fiber, palatability, and regrowth potential. Wait too long, and you end up with stemmy, coarse hay that horses pick through or reject — and that’s a waste of time and money.

Is Alfalfa Safe for All Horses?

While alfalfa is rich in nutrients, that doesn’t mean it’s safe or appropriate for every horse. Let’s break down who benefits — and who might not.

When Alfalfa Might Be a Problem

🟡 Urinary Stones (Calcium Overload)

Because horses can’t regulate calcium absorption like other species, any excess gets dumped into the urine. That’s what gives alfalfa-fed horses their cloudy urine — it’s calcium carbonate, and in alkaline urine, it can precipitate out and form stones.

Geldings are particularly at risk. Their urethra is long and narrow compared to mares and stallions, making blockages more likely. But any horse can develop kidney or bladder stones if calcium intake is excessive and water intake is poor.

🟡 Enteroliths (Gut Stones)

Feeding >50-70% alfalfa hay has been linked to enterolith formation, particularly in:

• Horses in California, Arizona, and other regions with hard water
• Horses kept in confinement with reduced gut motility

Why? Alfalfa raises colonic mineral concentrations and lowers pH, creating the perfect environment for stone formation — especially when combined with sand or lack of turnout. Arabians and their crosses seem especially prone.

That said, most horses fed alfalfa don’t develop enteroliths. It’s likely a combination of factors: high mineral intake, poor gut motility, limited movement, and lack of pasture access.

📌 Prevention tips:

Promote movement and avoid 100% alfalfa diets

Feed a mix of hays

Add apple cider vinegar (¼ cup/day) to acidify gut contents

🟡 Hoof Sensitivity

Some laminitis-prone horses seem to react poorly to alfalfa — even when NSC levels are low. Anecdotally, owners report hoof heat, tenderness, or even laminitis episodes after feeding it.

While the mechanism isn’t fully understood, one theory is that the excess of amino acid content stimulates insulin secretion, which is a red flag in insulin-resistant horses. If you see hoof sensitivity when feeding alfalfa, it is better to switch to grass hay.

New research (Loos et al., 2022) shows that alfalfa can spike insulin in IR horses to levels similar to an oral sugar test — despite having low NSC. This may explain why some metabolic horses experience hoof flare-ups even when sugar is controlled.

🟡 Respiratory Irritation

Alfalfa itself doesn’t cause coughing — but dusty, moldy alfalfa sure can.

Alfalfa is baled at slightly higher moisture than grass hay to keep the protein-rich leaves intact. This reduces dust if the hay is cured and stored properly. But if not, that extra moisture can promote mold growth and lead to heaves, coughing, or respiratory flare-ups. And this can happen to any type of hay, so it’s good to be on the look out for brown or grey spots in the hay, which can indicate mold so avoid feeding it.

🟡 Blister Beetles (Midwestern Problem)

In states like Kansas, Oklahoma, Texas, and Colorado, blooming alfalfa can attract blister beetles, which produce a toxin called cantharidin — a compound potent enough to be lethal to horses even in tiny amounts. Crushing the beetles during harvest releases this toxin into the forage, making contaminated hay especially dangerous.

Symptoms of cantharidin poisoning include:

• Mouth and tongue blisters
• Colic and diarrhea
• Bloody urine or urinary distress

What makes blister beetles even more dangerous is that they’re tiny and easy to miss. Once crushed into a flake of hay, they’re virtually undetectable to the naked eye. And contamination isn’t always widespread — you might only find them in one part of one bale, often where flowers and tender leaves are most concentrated.

➡️ Inspect every flake, especially in blooming alfalfa. The beetles are most attracted to flowering forage, and those flower-heavy pockets are where contamination is most likely.

Also, don’t assume hay from your local feed store is locally sourced. Alfalfa sold in your region may still come from beetle-prone states, depending on the supplier. That’s why it’s worth asking where your hay was grown and whether blister beetle management practices are in place.

While many growers take steps to minimize blister beetle contamination — like cutting before bloom or using equipment that limits beetle crushing — there’s no way to guarantee alfalfa is 100% beetle-free. If you live in a high-risk area or buy hay from those regions, extra vigilance is warranted.

🟡 Black Blotch Disease

While more common in clover, alfalfa can also develop black blotch disease in humid, warm conditions. Caused by the Cymodothea trifolii fungus, it can lead to liver damage and photosensitivity, especially in light-colored horses.

Does Alfalfa Make Horses “Hot”?

One of the most common beliefs is that alfalfa makes horses hot, spooky, or reactive. But is it true?

• Alfalfa is low in sugar and starch, so it doesn’t spike blood sugar: But this is only half true.
• Low sugar doesn’t mean low insulin. New research shows that alfalfa can cause an insulin spike — especially in insulin-resistant horses — due to its high protein and leucine content. (Loos et al., 2022)
  • Insulin spikes can drive reactivity in some horses — especially those already prone to metabolic or behavioral sensitivity. So while the link isn’t fully understood, some horses do become more “up” on alfalfa, even without high carbs.
• Although when horses become “hot”, it often comes from too many calories, not the forage type.

If your horse is overfed (regardless of feed type), you may see excess energy and excitability. Balancing the diet to match workload is key.

Understanding the Protein in Alfalfa

Alfalfa is rich in crude protein — and that’s not a bad thing. Horses use protein for:

• Muscle repair
• Growth
• Milk production
• Tissue maintenance

Alfalfa does contain lysine (the key amino acid for growth), but its small-intestinal digestibility is limited. If you’re feeding for muscle or development, consider pairing it with a ration balancer — which can deliver more usable amino acids with less total crude protein.

But excess protein can lead to:

• It increases urine output and stall ammonia levels
• May contribute to dehydration during intense exercise
• In endurance horses, heat increment from metabolizing excess protein may impair performance (Garlinghouse, 2001)

❗ Not all protein is digestible:

While alfalfa contains lysine, only ~21% of its protein is digested in the small intestine — the rest moves into the hindgut, where it’s fermented into ammonia. This can contribute to urine odor, dehydration risk, and kidney stress, especially when alfalfa is fed in large amounts or without balancing minerals. — the portion that matters most for growing horses (Gibbs & Potter, 2001). Complementary feeds like soybean meal, which have higher small-intestinal digestibility (~69%), may be needed to ensure adequate absorbable amino acids.

That fermentation produces ammonia, which is then excreted in the urine. This is why horses on alfalfa often have:

• More frequent urination
• Strong ammonia smell in stalls
• Cloudy urine (excess calcium being dumped)

The Calcium-Phosphorus Imbalance and Developmental Orthopedic Disease (DOD)

Alfalfa is naturally high in calcium — often around a 5:1 calcium-to-phosphorus ratio, while horses require something closer to 2:1. If left unbalanced, this can interfere with phosphorus absorption, especially in growing horses, and contribute to skeletal development issues.

But here’s the reason behind DOD: excessive energy intake. Overfeeding young horses — especially with high-calorie forages like alfalfa paired with grain — can cause a rapid growth and developmental orthopedic disease (DOD). Calcium and protein often get blamed, but they’re rarely the cause in isolation.

To support healthy bone growth, you need:

• Bioavailable amino acids (like lysine)
• Balanced minerals (especially calcium and phosphorus)
• Controlled energy intake to prevent growth spurts

How to feed alfalfa safely to young horses:

• Mix with grass hay to dilute calcium levels
• Add phosphorus-rich feeds
• Use a ration balancer to correct macro and trace mineral ratios

Alfalfa can absolutely be part of a foal or yearling’s diet — but it needs to be balanced with intent.

Gut Fill and Boredom

Idle horses have low nutrient needs but still require bulk (fiber) for digestive health and mental stimulation.

Idle horses don’t need the calories alfalfa provides, but they still need plenty of long-stem fiber to stay full and mentally stimulated. If you cut alfalfa too low without replacing the volume, you risk boredom, wood chewing, or digestive issues.

• Frustration and wood chewing
• Pica (eating manure, hair, or dirt)
• Colic or ulcers from insufficient chewing and saliva production

Combine alfalfa with lower-calorie, coarse grass hay to provide chew time and gut fill.

Best Practices for Feeding Alfalfa

Weigh your hay — don’t guess by flake

Start gradually to avoid digestive upset

Feed with grass hay to improve mineral balance and gut fill

Use a ration balancer or grain with added phosphorus for young horses

Avoid 100% alfalfa diets for horses

🔄 Feeding alfalfa before riding can help buffer stomach acid and reduce the risk of ulcers, especially in performance horses.

Conclusion: Should You Feed Alfalfa to Your Horse?

Yes — if it fits your horse’s individual needs.

Alfalfa offers exceptional nutritional value for performance, reproduction, and growth — but its richness can be excessive for idle or overweight horses. Be especially cautious with metabolic horses — insulin resistance changes how their bodies respond to protein, not just sugar. When in doubt, alfalfa might not be worth the risk for EMS or laminitis-prone individuals.

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