Alfalfa & Protein

by Lynda M. Vanden Elzen

We get a LOT of questions and comments from customers about feeding alfalfa to horses. There are many myths circulated about alfalfa, which is unfortunate, because it can be an excellent horse feed. Alfalfa is a legume hay that is generally low in sugars, has no fructans (a type of sugar), is high in calcium and quality protein, and because of its very deep root systems – up to 49 feet into the ground – alfalfa plants are able to access nutrients deep in the soil that other plants cannot.  Alfalfa can be a big help to horses who suffer from gastric ulcers, it provides abundant minerals and amino acids, and horses love to eat it!  Many horse people are afraid to feed alfalfa, so we’d like to present some information here on alfalfa and protein to help people to make educated choices about both.

a close up of alfalfa hay

alfalfa hay

Protein is made up of essential and non-essential amino acids. The horse’s body can synthesize some amino acids on its own, so those ones are called “non-essential” because the horse does not need to consume them in his feed. Essential amino acids must come from the horse’s diet. These are: arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Amino acids work together to form complete proteins, so if one is missing or in short supply, this limits the amount of protein available to the horse (or the human). Lysine is considered generally to be the first limiting amino acid, as it is not often found in large enough quantities in many feeds. This limits the overall protein content in that feed that is available to the horse. Other limiting amino acids tend to be threonine, methionine, and tryptophan.

From, “Understanding Amino Acids” by Shannon Pratt-Phillips, PhD:

“When formulating a diet for horses to meet their protein needs, we really are formulating a diet to meet their essential amino acid requirements, and to provide a nitrogen source for non-essential amino acid synthesis… Equine feedstuffs vary greatly in their protein content and in their amino acid profiles. Plants differ in their ability to synthesize amino acids, resulting in some differences we see among plant-derived proteins. Legumes, such as alfalfa (alfalfa hay) and soybeans (as found in soybean meal) have a unique symbiotic relationship with Rhizobia bacteria, which allows them to take up ample quantities of nitrogen from the soil, and, as such, they have a greater ability to produce amino acids, and protein in general, than other plants (such as grasses and grains). As a result, feeds such as alfalfa hay have higher amounts of protein than grass hays (such as timothy or orchardgrass)…”

From Sally Hugg’s article, “Healthy Horses = Healthy Hooves“:

“According to the National Research Council (NRC) guidelines, a mature horse needs approximately 21 grams of lysine daily for maintenance. At best, grass hays contain 0.1-0.2% lysine, however 6 lbs of alfalfa could supply the lysine needs of that horse.”

By comparison, 6 lbs of a good grass hay might contain only 2.2-4.5 grams of lysine.

As with most everything to do with horses, the key is to find a balance.  Too much alfalfa can be as damaging as not enough.  Alfalfa, in addition to being an excellent protein source with low sugar levels, tends to be high in energy and calcium.  Too much of a good thing is not always better! The high calcium levels in alfalfa carry with them the risk of entroliths (hard spherical mineral deposits that can form in the horse’s digestive system, often around a foreign body like a small piece of wood), and feeding protein in excess of the horse’s needs can cause problems too.  According to Dr. Juliet Getty, “The metabolites of amino acid degradation can potentially lead to excess glucose in the blood.”  In other words, feeding protein is great.  Feeding too much protein is not better.  How much is too much depends on your horse as an individual: his breed and lineage, age, activity level, metabolism, etc.  

Dr. Getty also suggests, in her article, “Alfalfa and the Insulin Resistant Horse – The True Story” that alfalfa sprayed with propionic acid can be a problem for insulin resistant horses:

“Alfalfa is often sprayed with buffered propionate (also known as propionic acid) to retard spoilage if baled during wet or humid conditions… Not considered to be harmful, propionate is one of three volatile fatty acids (VFA) naturally produced by the hindgut bacteria during hay fermentation. The other two VFAs are acetate and butyrate. These VFAs are a significant energy source for your horse. Acetate is utilized by many tissues including the heart, muscles, and the brain. Butyrate provides energy for the cells that line the hindgut epithelium. Propionate is a major precursor toward glucose production through a process known as gluconeogenesis. And that’s a problem for the IR horse. Once propionate is absorbed and metabolized, it is converted to glucose! So when you feed alfalfa that has been treated with propionic acid, you are essentially increasing your horse’s blood glucose level, just as you would if you had fed a hay with a large amount of sugar and starch. Increased glucose leads to increased insulin.”

There is a lot of information out there about alfalfa.  Some of it is true, and some of it is not so true.  Our approach is to read the most up to date research and information, and to consult with equine nutritionists and nutrition-savvy veterinarians, so that we can help our customers to decide on the best diets for their horses.  Every horse is not the same, and so we do not believe in cookie cutter one-size-fits-all approaches to feeding horses.

For further information and reading regarding protein and alfalfa, please check out the articles cited below under “Sources / Suggested Reading.”  In addition, we have found an excellent article overview from Canadian Horse Journal on alfalfa and protein and many myths about both that circulate through the horse world.  It can be found by clicking on the image below:


As always, we welcome comments and questions, which can be submitted at the end of this article.


“Understanding Amino Acids” by Shannon Pratt-Phillips, PhD (

“Healthy Horses = Healthy Hooves” by Sally Hugg (

“Alfalfa and the Insulin Resistant Horse – The True Story” by Dr. Juliet M. Getty, PhD (

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I have really struggled with keeping weight on my senior thoroughbred. For the last year i have been feeding him 2 flakes of Alfalfa hay every morning and he looks amazing now. So many people are so agsinst alfalfa but i wish i haddone this long ago fo this horse it has made all the difference !….Amy


Hello Amy, Lynda here. That is great to hear how well your horse is doing! It is unfortunate that alfalfa gets such a bad rep. It can be an important part of a balanced diet. There was a gal who I met at a local horse show last year. We had a table there to showcase some samples of our hay and information on hay testing, so she and her mom asked me to take a look at their horse. He had significant muscle wastage along his topline and elsewhere, and their barn fed straight untested timothy. They were worried about him and asked what I thought might help him, so we got him onto a higher protein 2nd cut alfalfa mix hay. I ran into the same gal again on Boxing Day and she told me her horse had changed so much her saddle fitter didn’t recognize him!


I have a 5yr old AQHA gelding. He holds his weight better on alfalfa but if I feed him a larger amount of alfalfa his hind legs swell. If I back him off the swelling goes away.


Hello Kristy – Lynda here. That is interesting! Have you by any chance been feeding tested hay when this has happened? I would be interested to see the protein levels in the hays that have caused this. Were you feeding straight alfalfa and mixing with a grass hay or were you feeding an alfalfa mix? Also, is the horse stalled/confined to a small paddock some or all the time, or is he living in a herd situation? And what else is he eating? Thanks for the comment!

Joan virden

I have fed straight alfalfa from our wonderful fields in Fallon, NV. For 35 years. My horses have so far been healthy and happy. Only had a grass belly problem when I switched to grass hay for one summer.


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