Why I don’t feed alfalfa … I can’t afford it!

November 28, 2011

Why I don’t feed my horses alfalfa …

Is Alfalfa really a good food for horses?  Not in my barn!  Alfalfa may cost less than grass hay. It may be considered a standard forage for horses, but more and more researchers, trainers and breeders are figuring out that it has long term costs that outweigh the initial savings.  What do we have against alfalfa?

There are a variety of reasons that you should not feed straight alfalfa, ranging from diminished performance to colic and increased incidence of disease.

Primarily, alfalfa is too high in protein for the average equine diet.  Alfalfa hay generally runs at least 18-20% protein, often higher.  Mare’s milk is only about 8 – 11% protein, and, unless performing at levels far above those experienced by a normal horse, a horse never requires more protein than they receive from Momma.  Mother Nature doesn’t make many mistakes!

A study at University of Maryland by Dr. Michael Glades concluded that horses with excess protein in their diets ran slower race times than horses receiving the Natl. Research Council’s recommended amounts. He found that for each kilogram of crude protein that a horse ate above his basic needs, the racing times slowed dramatically, as much as 1 to 3 seconds.  

Dr. Kerry Ridgeway points to an all-alfalfa diet as the cause of higher body temperature in working horses, caused by the extra work required by the internal organs to convert the protein to usable energy. He feels this leads to excess sweating and electrolyte loss, which can in turn lead to dehydration, impaction and colic.

High protein diets require more stomach acid to be digested.  Equine bodies (like ours) need to be on the alkaline side in order to survive; a high protein diet triggers emergency responses in the system.  The cells hold on to excess water to dilute the acid.  The body pulls minerals from the bones in order to buffer the acid.  As the tissues and bones become de-mineralized, ligaments become slack.  The joints begin to click, or the horse develops a sore back because the muscles are having to do the work that the ligaments should be doing.  As time goes on, the body attempts to stabilize the joints by building up calcium. This shows up as problems such as ring bone, spavins, and navicular syndrome.

Low pH (high acid) is also related to all the body’s “itises” – arthritis, tendonitis, gastritis, bursitis – all can be shown to be tied to a overly acidic body.

If your horse’s stall smells like ammonia, he is in trouble from too much acid in the body. Also present in alfalfa hay is actually non-protein nitrogen and/or nitrates, which are toxic to horses.  In an effort to get rid of excess protein and these related substances, the body produces ammonia.  This is very hard on the kidneys, and can also lead to respiratory problems from inhalation of the ammonia fumes.  Healthy urine should be clear, not cloudy and foul-smelling.

Hypothyroidism, thumps, “bad attitude”

Fresh AlfalfaAnother issue with alfalfa as a primary food is its high level of calcium.  According to Dr. Ridgeway, the excess calcium in an alfalfa diet interferes with parathyroid function and can lead to “thumps”, muscle cramps and tying up.

Excess calcium interferes with iodine absorption, an element necessary for proper thyroid function. Many horses on alfalfa become hypothyroid – the thyroid gets lazy. Symptoms can be a cresty neck, a horse that gets overweight very easily, develops dry and flaky skin.  Some breeds show hypothyroidism by becoming very “cinchy” and skin-sensitive, getting cranky when being groomed, or losing topline muscle and hair condition. Mares that are hypothyroid often become infertile.

Horses that are hypothyroid may be very plump and shiny, but are unhealthy. They are simply retaining water in the tissues, and this inhibits proper movement. Ask any woman with P.M.S. how she feels when she is retaining water!  If your horse is cranky and belligerent, resists bending and flexing, is very lazy or reacts emotionally, it may be a sign of a sluggish thyroid.

Tying Up – Contracted Tendons

T. J. Hulland, a researcher at the University of Guelph-Ontario, feels that most “contracted tendons” in young horses are the result of contracted muscles in the forearm and gaskin. The tendons and ligaments themselves are not capable of shortening, but it is possible for a young horse that is getting too much calcium and protein to have the tight muscle, or borderline “tie up” condition. If the problem is caught early on, dietary changes can often prevent permanent damage. By reducing the protein content of the ration (replacing alfalfa hay with mostly grass hay) and bringing the calcium/phosphorous ratio closer to the ideal (1:1), and providing balanced minerals in a usable form, the foal is allowed to develop more normally.

Just like us, horses need fiber

Horses need adequate fiber for their digestive system to function properly.  Alfalfa is quite low in fiber. Horses on an alfalfa diet are usually done eating in a hour or so.  Nothing enters the tract until the next feeding, many hours later. This predisposes a horse to colic.  With quality grass hay, the horse is able to “graze” on it all day, and does not become ravenous and gobble feed.

Increased Incidence of Disease

Dr. T.W. Swerczek at the University of Kentucky feels that a diet high in protein and low in fiber can predispose stressed horses to become ill. Among the disorders he listed are Potomac horse fever, strangles, salmonella, ulcers, abortions, epiphysitis.  Stress factors can be weather, hauling, competing, even changing pasture companions.

Dr. Swerczek experimented with the diets on research horses that he infected with strangles. He divided them into two groups, and fed one group alfalfa and the other group grass hay. The horses fed alfalfa became so ill that even vaccines and antibiotics did no good. Yet, when he took away the alfalfa and high protein supplements, the disease disappeared on its own. The horses on grass hay experienced a very mild case of strangles that did not require any treatment.

He also feels that in the lactating mare, if the mare’s kidneys are overloaded with high protein, the toxic metabolic wastes may be passed on in the milk and affect the health of her foal. Unhealthy foals with low grade colic or muscle aches from coughing can develop abnormal holding patterns in their bodies, which lead to faulty muscle development and crooked legs.


Enteroliths can completely obstruct the intestines.California and the West where straight alfalfa diets are common have the highest incidence of “stones” in the country.  Enteroliths are intestinal stones formed from ammonium magnesium phosphate. The ammonium comes from the excess protein in the alfalfa. Another contributing factor is the low fiber in alfalfa, which keeps the gut from functioning properly and allows the stones to form. Dr. Robert Bray at Cal Poly University recommends cutting back on the alfalfa portion of the ration as a means of helping to prevent stones. Research has shown that horses with a history of forming stones cannot tolerate any alfalfa without a recurrence.

In conclusion

Over acid conditions and calcium imbalances have been shown to lead to many health concern when alfalfa is fed as the main diet to horses.  So why don’t I feed alfalfa?  I can’t afford it!!

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  • Bray, Dr. Robert E. “Enteroliths: A Potential Problem With Horses”. Article prepared for EquiTech Conference, Los Angeles, CA. Nov. 1993.
  • Hayes, Karen E. N., D.V.M. “Don’t Let DOD Derail Your Foal”, Modern Horse Br eeding. May 1992.
  • Hayes, Karen E. N., D.V.M. “The Great Hay Debate”, Horse and Rider
  • Hudson, Mary “Subtle Signs Of Lameness In Foals And Weanlings”, Modern Horse Breeding, Smith, Carin A., D.V.M.
  • “Is Your Horse Hypothyroid?” Horse Illustrated January 1994 Stewart-Spears, Gene “Disease Linked To Nutrition”, The Chronicle of the Horse. January 1992
  • Thompson, Diana “Too Much Of A Good Thing”, AERC Endurance News. October 1992
  • Vandergrift, Bill, PhD. “Helping Horses That Tie Up”, Modern Horse Breeding, September 1994

{ 3 comments… read them below or add one }

Lorraine December 15, 2012 at 1:38 am

Thank you for a very informative artivle – will definitely keep it in mind.


Clair December 10, 2011 at 3:15 pm

This his article does a nice job of covering the potential pitfalls of alfalfa from all angles. However I think it is important to understand that there are many good quality cuttings of grass hays that are as high in protein as lower quality alfalfa. I commonly test orchard grass hays in California that test 15-16% crude protein and therefore the same issue apply.

Growing weanlings require more protein in their diet than they get from mares milk, they require 14-16% crude protein in the diet. This requirement coincides with around the time they start eating forages and in native situation is the time forages are growing and have high protein levels. The “natural” diet of horses is high protein but on a seasonal basis in the spring not year round.

I personally believe that alfalfa has a place in some horses diets but not as the sole forage and I prefer to not see it above 25% of the forage intake. The amino acid profile is better than grass hay as it contains more lysine which is the most commonly limiting amino acid.

One thing I would add to this article is that typically the caloric content of alfalfa is higher than grass hay pound for pound so it makes it unsuitable for easy keepers or it means you have to feed less of it to prevent them getting fat which is don’t like doing.

Clair Thunes, PhD
Independent Equine Nutritionist
Summit Equine Nutrition


Kay Aubrey-Chimene, Publisher December 11, 2011 at 9:48 am

Hi Clair – I really appreciate your input – while we may take a different approach – it is so great to see equine nutrition being taken seriously outside of the typical nutrition taught at Universities which is based upon feed-lot cattle.

I don’t agree that weanlings need more protein than they got in nature – and can’t see that they got higher protein when in the wild. And there is still a big difference between 14 – 16% protein grass hay with a more appropriate Ca/P ratio than 18 – 24% alfalfa with out of balance Ca/P ration. And seeing how almost all alfalfa is force grown with massive amounts of inorganic nitrogen (which is why it is that pretty blue color), it also puts much more pressure on the kidneys to process out all the resulting ammonia.

While some horses can handle the additional stress of alfalfa, I have literally never had a horse muscle test for it. I realize that muscle testing may be different approach for many people – but here at the ranch we allow each body to direct what strengthens it most nutritionally by muscle testing what goes into the feed. We kept alfalfa on hand for a few years to test horses for it if it was appropriate – and it just never tested strong for them.

The horses that I have seen do best on an alfalfa or partial alfalfa diet are ones getting enough exercise (high amounts) to flush that ammonia out of their system. Also – the hotter the breed (i.e. Arabians vs Warmbloods) the more sensitive they seem to be to the alfalfa.


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