High-Protein Hay: The Types and the Horses That Need It

Last updated: November 12, 2026

By: Miles HenryFact Checked

Alfalfa is usually the first hay that comes to mind when you’re looking for more protein for your horse. But does your horse need it? Before you pay more for high-protein hay, know which types offer the most protein and when that extra protein matters.

Here’s how the common hays compare, which horses benefit, and what too much or too little protein looks like.

Protein Content of Common Hays

These are general ranges, not guarantees. The alfalfa and grass ranges are from University of Georgia Extension, and the red clover range and oat hay notes are from Cooperative Extension. Protein changes with the variety, soil fertility, growing conditions, and especially when the hay is cut. Use the table as a reference, not a substitute for testing your own hay, and check whether a lab reports results on an as-fed or dry-matter basis before you compare them.

Maturity makes a big difference. In Oklahoma State data, bermudagrass fell from 21.4% crude protein after one week of growth to 12.2% at eight weeks, and nitrogen fertilizer raised it. Those are research results, not a prediction of what your hay will test, but they show how much maturity and growing conditions can change the number. Leafy hay cut early is higher in protein than stemmy hay cut late, so the name of the hay won’t tell you what’s in the bale.

Alfalfa is different from grass hay in more than protein. It’s nearly always higher in calcium, too, according to The Horse, and legumes tend to have more lysine, an essential amino acid, than grass hays, according to equine nutritionist Clair Thunes. It’s also more energy-dense than most grass hay. That makes it useful for some horses, but it isn’t automatically the best choice for every horse.

If you’re looking at clover hay, know which clover it is. Alsike clover has been linked to sun sensitivity and liver damage in horses, and Ontario agriculture officials advise keeping it out of horse hay and pasture seed mixes.

Which Horses Need High-Protein Hay?

If you’re shopping for high-protein hay for horses, alfalfa is the usual answer, followed by alfalfa-grass mixes and red clover. A leafy, early-cut, well-fertilized grass hay can also test surprisingly high.

The horses most likely to benefit are:

• Growing horses. Weanlings and yearlings are building muscle and bone and need more protein and lysine than adults.
• Broodmares. Protein needs go up in late pregnancy and even more during lactation.
• Hard keepers. Alfalfa can help a horse that struggles to hold weight because it has more calories and more protein than most grass hay. If the horse already gets enough protein, the extra calories are the bigger benefit. Not every thin horse is short on protein.
• Horses on poor-quality grass hay. Mature, stemmy hay cut late can come up short even for a horse at maintenance.

An adult horse on good grass hay doesn’t automatically benefit from switching to alfalfa. If a hay test shows a gap, a little alfalfa mixed with the grass hay can fill it, and so can a ration balancer. A low-intake balancer can help supply amino acids when good forage isn’t available, according to Kentucky Equine Research. The pros and cons of feeding alfalfa are covered in alfalfa hay for horses: the good and the bad.

How Much Protein Does a Horse Need?

Less than most people think. A mature horse at maintenance needs a diet with about 8 to 10% crude protein, and exercise raises that only slightly, according to Cooperative Extension. Growing horses and mares in late pregnancy or lactation need more, up to 16% at times. Treat those percentages as general guidelines, not rules for every horse.horses.extension

Those percentages describe the whole diet, not just the hay. A horse’s needs depend on his weight, age, and workload, while how much he eats determines how much protein he gets.

Hay, pasture, and any grain or balancer all contribute protein. Judge the whole ration instead of the number on one feed tag.

Grass hay can be a good choice for easy keepers, too, though you should test the batch rather than assume a particular hay is low in calories or sugar. More on that in the best hay for overweight horses.

Symptoms of Too Much Protein in Horses

There’s no reliable set of outward symptoms that proves a horse is getting too much protein. A horse doesn’t store the extra. It breaks down the amino acids it doesn’t need and gets rid of the nitrogen as urea in the urine, according to The Horse. When that happens, you may notice:

• More urination and wetter stalls. You’ll go through more bedding.
• More drinking. Some horses drink more on a high-protein ration, so keep fresh water in front of him.
• More ammonia in the bedding. Urea in wet bedding breaks down into ammonia, which can irritate a horse’s airways.

Those signs can have other causes. Conditions such as PPID (equine Cushing’s) can also increase drinking and urination, so if it keeps up, call your vet. Whatever the cause, don’t ignore an ammonia smell. Pick out wet bedding often and keep the barn well ventilated.

For a healthy horse with plenty of fresh water, extra protein generally isn’t harmful. Horses with existing kidney problems are a different matter, according to Extension, and their diets should be managed with a vet. Extra protein can cost you money and bedding without building extra muscle.

Here’s an Ask the Vet video on horses that get too much protein:

Signs a Horse Isn’t Getting Enough Protein

Protein deficiency is less common than excess, but it can happen when a horse eats poor hay or doesn’t get enough protein for his stage of life. A horse short on quality protein may lose muscle along the topline, develop a dull coat, or grow poorly if he’s young. Poor topline muscling and a dull coat together could point to a need for higher-quality protein, according to Thunes.

None of those signs is specific to protein. Parasites, bad teeth, ulcers, and too few calories can cause the same things, so have your vet look before you change the ration.

What Crude Protein on a Hay Test Means

Crude protein is an estimate, not a direct measurement. Labs measure the nitrogen in a hay sample and multiply it by 6.25, according to Extension. Not all of that protein is digestible.

Protein supplies the amino acids a horse needs to build and repair muscle and to grow a healthy coat and hooves. When you read a hay analysis, compare crude protein on a dry-matter basis. That puts hays with different moisture levels on the same footing, and the as-fed number will always read a little lower.

How to Test Your Hay

Leafiness, texture, and smell help you judge hay, and they’ll show you dust, mold, and stemmy, overmature bales. They won’t tell you the protein content, and neither will color alone. A hay test will.

To test your hay, use a hay probe to pull cores from 10 to 20 bales per lot, mix them in a clean bag, and follow the lab’s instructions for sending the sample. A probe gives you a better sample than handfuls pulled from the outside of a bale. Don’t combine different cuttings or loads. Your county extension office can usually point you to a lab and help you read the results. Test each new lot, since protein can change from one load to the next.

A hay analysis reports more than protein. Look at dry matter, digestible energy, the fiber numbers (ADF and NDF), and, for easy keepers and metabolic horses, sugar and starch (NSC). Don’t pick hay on protein alone.

Check bales for mold before you feed them, too, and know what to do about moldy hay. Many adult horses eat about 1.5 to 2% of their body weight in forage dry matter a day. The as-fed weight will be higher, depending on the hay’s moisture content, and how much hay to feed a horse depends on the horse and the hay.

Miles Henry

About Miles Henry

Racehorse Owner & Author | 30+ Years in Thoroughbred Racing

Miles Henry (legal name: William Bradley) is a professional horseman based in Folsom, Louisiana. He holds Louisiana Racing License #67012 and has spent over three decades managing Thoroughbreds at premier tracks including Fair Grounds, Delta Downs, and Evangeline Downs.
Expertise & Hands-On Experience: Beyond the track, Miles has decades of experience in specialized equine care, covering everything from hoof health and nutrition to training protocols for Quarter Horses, Friesians, and Paints. Every guide on Horse Racing Sense is rooted in this “boots-on-the-ground” perspective.
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