Call us 24/7 - 1-800-461-8898

Ask the Vet: Choosing a Muscle Supplement for Your Horse


I’m looking to help my horse build muscle along his topline and hindquarters for show season this year. I’m very confused by all of the different muscle supplements on the market and I’m not sure what is important? What ingredients do you recommend for helping horses to build and maintain muscle? – LP, Illinois

Dear LP,
Healthy muscle development requires both stimulus and building blocks. By “stimulus” I mean exercise or work, and by “building blocks” I mean dietary protein or amino acids. I’ll leave it up to you and your trainer to put together a sound conditioning program for your horse and just speak to the nutritional aspect of your question.

My go-to source for all things equine nutrition is the NRC’s Nutrient Requirements of Horses. This resource says an 1100lb horse in light exercise needs a minimum of 700 grams or about 1.5 pounds of protein per day (forget percentages like 10% and 12%), with 30 grams of that required specifically as lysine, the first “limiting” amino acid.

What does “limiting” mean? According to the NRC, a limiting amino acid is one that, when it is present in less than adequate amounts, will limit protein synthesis. In practical terms, if your horse’s diet is deficient in lysine, he cannot build muscle since this amino acid must be present for any tissue development to take place. A team of researchers conducted an experiment to see if supplementing with lysine (and threonine, the third-most limiting amino acid) would help older horses maintain muscle mass:

Graham-Theirs PM, Kronfeld DS, Hatsell C et al. Amino acid supplementation improves muscle mass in aged horses. J Anim Sci. 2005 Dec;83(12): 2783-2788.

Turns out they got more than they bargained for! The research study showed that horses receiving supplementary amino acids were able to maintain muscle mass better than those without supplementation, regardless of age, as evidenced by improvement in muscle mass scores (and other parameters).

This tells me that providing horses with the first three limiting amino acids—lysine, threonine and methionine—is a smart thing to do if you want to build or maintain muscle. In fact, it probably makes sense to provide all ten of the essential amino acids in the horse: histidine, isoleucine, leucine, valine, lysine, tryptophan, phenylalanine, threonine, methionine, and arginine. “Essential” means the horse requires these ten specific amino acids be provided by the diet, preformed and ready to use. Non-essential amino acids are those the horse can synthesize himself. There are about ten of those, too.

How do you make sure your horse is getting all ten essential amino acids, but especially the most limiting, lysine? While soybean and alfalfa are two examples of high-quality protein sources for horses, bio active whey is actually one of the best sources of protein, with more lysine and other essential amino acids than any common equine feedstuff. So in your particular situation, I recommend you work with your veterinarian and a nutritionist to make sure your horse’s diet is complete and balanced for ALL nutrients, then look for supplements that can be added to ensure adequate levels of protein building blocks are supplied without unbalancing the diet in some other manner. By the way, “high quality” refers to the type, amount, and balance of amino acids in a protein source. The more essential amino acids—especially the limiting ones–the higher the quality. Good luck and have a great next show season!

Lydia F. Gray, DVM, MA SmartPak Staff Veterinarian and Medical Director Dr. Lydia Gray has earned a Bachelor of Science in agriculture, a Doctor of Veterinary Medicine (DVM), and a Master of Arts focusing on interpersonal and organizational communication. After “retiring” from private practice, she put her experience and education to work as the American Association of Equine Practitioner’s first-ever Director of Owner Education. Dr. Gray continues to provide health and nutrition information to horse owners through her position at SmartPak, through publication in more than a dozen general and trade publications, and through presentations around the country. She is the very proud owner of a Trakehner named Newman that she actively competes with in dressage and combined driving. In addition to memberships in the USDF and USEF, Dr. Gray is also a member of the Illinois Dressage and Combined Training Association (IDCTA). She is a USDF “L” Program Graduate and is currently working on her Bronze Medal. Find Dr. Gray on Google+

Posted in Ask the Vet, Weight Management

Recent Posts

One comment on “Ask the Vet: Choosing a Muscle Supplement for Your Horse
  1. Robert Corbett says:

    This was a great article. As with most of these articles, they are both informative and provide educational resources to help the horseman provide essentially better care of his horses. I always enjoy learning new things that improve my knowledge and make taking care of my animals more interesting and productive. Thank you for your teachings and knowledge shared with us. Robert Corbett

Leave a Reply

Your email address will not be published. Required fields are marked *


Share it:
You'll this

SmartCombo™ Senior Pellets

As Low As: $57.95
(266 reviews)
Healthy Horses  ❤  Happy Riders