Decomplexicating Equine Nutrition Part 08 of 12 – The Importance of Protein

When discussing nutrition, most people know more about sugar as it is in the news every day. Fats are also discussed in terms of good and bad fats. However, when it comes to proteins, most people immediately recite the % protein content of the feed they are giving to the horse. So let’s start there.

Crude Protein

When a bag of anything says % crude protein, what they are telling you is if they took a quantity of that feed (grain, hay, potato chips, soda – anything) and burned it to nothing, they would measure the amount of Nitrogen burned off. Comparing that amount against the total amount would yield a %. Nitrogen is only found in air and in protein so the assumption is that any nitrogen found in the burn-off is related to protein. Dog food made outside of the United States was infused with urea which is toxic to animals and is made with Nitrogen. When this food was analyzed the % protein was listed higher than it really was as it only measures the Nitrogen and not the ingredient it came from. This dog food killed dogs and has been removed from the market.

The result is that when you purchase any food for the horse that is a mix of ingredients, you need to read that ingredient list to determine the source of nitrogen. What I mean by a mix of ingredients is any bag of grain or supplements or treats. Usually, the crude protein of all hays is a reflection of hay protein but of grain, the protein sources could be from alfalfa pellets, soybeans, corn, or wheat middlings. This makes a big difference because the proteins from each of these ingredients are absorbed differently.

To put it in a simpler way, not all proteins are the same! Therefore not all proteins are absorbed the same way. So far, you now know that feeding “12%” protein doesn’t tell you anything. You MUST know the ingredients to determine how much protein your horse is actually getting.

Amino Acids

Remember in past blogs that the gut wall is very thin with tight junctions whose main purpose is to keep bad things out of the body but also let in good things like the raw materials called nutrients? Proteins consumed whole are very large molecules that cannot pass through the gut wall. So how do they get in? There are two ways but both are part of one process. Like two ways to get to the local store – by car or by horseback. The process is to take every protein in food and break them down into individual parts called amino acids. These are small enough to be taken through the gut wall and into the body where the horse assembles them back into the proteins they need.

To repeat, every protein consumed by the horse is taken apart or disassembled into tiny pieces, transported across the thin gut wall and then reassembled on the other side, within the cells of the horse and by the cells of the horse into the specific proteins it needs. This process happens with every protein consumed but it is more efficient with some proteins than with others. This efficiency is called the biological value of the protein and egg white is the standard with 100% efficiency. Every bit of egg white will be absorbed across the gut wall and into the horse. 94% of whey protein will be absorbed. 80% of soybean protein will be absorbed. About 50% of grass and alfalfa protein will be absorbed.

In other words, if a pound of each protein source is fed to a horse, the following amounts will be absorbed: egg 1 pound, whey 0.94 pound, soy 0.8 pound, and hay/pasture 0.5 pound. The ingredients matter, not just the crude protein. If you feed a pound of bagged food containing 14% crude protein and the ingredient source of this protein is only alfalfa meal, then the net absorbed protein is 14% of 1 pound (0.14 pound) times 50% absorption yielding 0.07 pound absorbed protein per pound of feed given.

Hold this thought that only a portion of the protein fed is actually absorbed. I’ll get back to this in a moment but I said that there were two paths within the same process of getting proteins into the horse. The process involved breaking them down into amino acids and transporting these to the cells where they are assembled into proteins again. But amino acids come in two types: those that can not be made by the horse (essential amino acids) and those that can be made (non-essential amino acids). It is the essential group that needs to be fed in enough quantities to effectively make the proteins the horse needs. Out of the 20 total amino acids that make all of the proteins in the horse, 10 need to be consumed by the horse and the other 10 can be made from the atoms inside the cells. 3 of these essential amino acids are called “limiting” amino acids because they are limited in the food sources of horses.

Making matters of protein manufacturing more difficult is that every protein made needs all the amino acids needed for that protein.

For example, what if I wanted to write this blog but my computer could not type the letter “e.” The sentence would look like this:

For xampl, what if I wantd to writ this blog but my computr could not type the lttr “e”.

In other words, if the horse is missing or is limited in even one essential amino acid, then there are a lot of proteins not being made. To get these limiting amino acids the horse can do two things. The first is to consume them by finding them in his environment and the second is to recycle the essential amino acids already in the body. The recycling program is very effective and works well but there is always some attrition so the horse still needs to take in some of these essential amino acids. See Fact 5 below for more on this important point.

Interesting Facts About Proteins

Before looking at why most horses today are protein deficient, let’s review what we do know and add some more facts.

Fact 1 – Proteins are very important in the body making up every working part including immune system molecules, hormones, neurotransmitters, connective tissue and hair and hooves. Think of sugar and fat as fuels. Also, think of fat as cell walls and insulation around nerves. Think of everything else as proteins.

Fact 2 – Proteins are very small but too large to be absorbed through the gut wall. They have not been photographed or seen in a microscope. There are estimated to be between 1 and 3 BILLION proteins within every cell. For perspective, count how many molecules of gasoline are in the filled gas tank of your car.

Fact 3 – Proteins have a life span. With the exception of hair and hooves, the life expectancy of a protein is about 2 to 4 days. When the protein life is over, the amino acids go into the recycling program and are used to make new proteins.

Fact 4 – A very interesting fact about horse hooves is that 24% of the hoof is made of 1 amino acid – cysteine. It is the only amino acid that has a Sulfur molecule in it that can make a special bond that folds and strengthens it adding rigidity to the hoof. But the horse can only make cysteine if he eats protein with the essential amino acid methionine. This essential amino acid has the Sulfur atom but cannot make this special bond so the horse converts it into cysteine before making the protein of the hoof. Oh, and guess what? Remember that I said there were 3 limiting essential amino acids in the horse’s environment? One of them is methionine. The result of taking in food (raw materials) low in methionine is poor hair coat and hooves.

Fact 5 – If you are low in one amino acid then you will be low in all the amino acids even if they are available in abundance. This makes a lot of sense once understood. The best way to describe this is to think of a protein as a word and the amino acids as the letters making that word. For example, HORSE is made of one letter each of H, O, R, S and E. If I gave you 7 H’s, 16 O’s, 7 R’s, 4 S’s and 30 E’s, how many times would you be able to spell “HORSE” The answer is 4 because you only have 4 S’s. You might be able to make some other words such as “HOE” and “HERO” but you cannot make another “HORSE.” Therefore the S is a limiting letter and if it was an amino acid, it would be a limiting amino acid. Not all proteins eaten as raw material will have all the essential amino acids needed to build all the proteins that make a horse work and remain healthy. This is why a horse needs to be fed a wide variety of proteins to supply a wide variety of proteins. Soybean is the least expensive, most abundant and most complete protein source for horses with high bioavailability.

Fact 6 – The body can take protein in the form of muscle and convert it into 2 products: glucose and urea. This is called gluconeogenesis (glucose new birth). The glucose is used for energy in the mitochondria and the urea is excreted in the urine giving the ammonia smell in the closed barn in the winter.

Fact 7 – The daily requirement for protein intake to replace amino acids lost in attrition is debated in the human world Several factors need to be looked at and will be covered in the next section. According to the National Research Council which sets the standards for animal nutrition, the recommended daily intake is 0.5 to 1.0 grams of protein per pound of body weight. This is also a recommendation for humans. Using the example above where a horse is being fed a 14% protein mix with alfalfa meal as the protein source, it was determined that the horse would receive and absorb 0.07 pounds of protein for every pound of mix fed. Let’s convert 0.07 pounds to grams. If 1 pound = 454 grams then 0.07 pound = x grams (1/454 = 0.07/x, x = 454 * 0.07, x = 31.78 grams). If a 1000-pound horse needs 0.5 to 1.0 grams per pound, then the requirement is between 500 and 1000 grams of protein per day. For fun, let’s divide 500 required grams by the 32 grams he is getting in 1 pound of the mix. The minimum pounds of mix needed to meet this requirement would then be 500 / 32 = 15.6 pounds of mix per day. BUT HOLD ON! Does the alfalfa protein have ALL the amino acids the horse needs? No, it doesn’t.

Why Protein Loss Occurs In Horses Today

It is obvious that a horse that doesn’t get fed enough protein will become protein deficient. More importantly, even if a horse is fed “enough” protein by calculations, it may not be ingesting enough of the essential amino acids, especially the 3 limiting amino acids (see fact 5 above). Unfortunately, there is no test available to determine if your horses are getting every amino acid they need. Instead, we just need to look at some of the diseases they suffer from when they don’t have enough protein. Here is a partial list. Some of these diseases may be directly from an absence of a protein and others may be from a cascade of events in which protein deficiency is only a part of the disease.

  • Poor hair coat (unthrifty, scaly, rough, lackluster)
  • Skin conditions (rain rot, scratches, ventral midline dermatitis, the crud, itchy horse)
  • Poor hooves (cracks, splay, dropped sole, laminitis, shelly, thrush)
  • Poor topline (prominent withers, prominent backbone, sway back, kissing spine)
  • Lame (all connective tissue causes including suspensory desmitis, bowed tendons, dropped fetlocks, joint dysfunction, muscle soreness, separation of the coffin bone from the hoof)
  • Immune dysfunction (increased cortisol or Cushing’s, neurotransmitter deficiency, gut problems, parasite load)
  • Cancer (canker, melanoma, sarcoid, pythiosis or summer sores)

If your horse has any of these issues then your horse may have a protein deficiency. Let’s look at some of the reasons for this.

1) Your horse is being fed a limited amount of a variety of proteins. This leads to an overall deficiency in materials to build all the needed proteins. Remember the idea that a deficiency of one amino acid is equal to a deficiency in all amino acids (fact 5 above). This leads to a deficiency of every amino acid and subsequently a deficiency of every protein made with the limiting amino acid.

2) Your horse is being fed a proton pump inhibitor which is basically anti-ulcer medication (omeprazole, Prilosec, Peptid AC). These types of drugs will make the pH of the stomach less acidic which prevents the breakdown of the large proteins into smaller peptides and smaller amino acids. This sends the proteins down the gut in their intact form which is indigestible. The result is the same as not feeding the horse protein and a deficiency occurs.

3) Your horse has an inflamed gut with altered gut bacteria (microbiome). This will lead to inefficient absorption of all nutrients including any amino acids that may get to this point. Again the result is a decreased uptake of the materials to build proteins within the body.

4) Your horse is overwhelmed with a disease or stress or both. These will increase the consumption of proteins. This includes over-working the musculoskeletal systems which lead to connective tissue breakdown. It also includes a load of parasites in the environment that the horse’s immune system is desperately fighting consuming a lot of protein as it does so. Hence the poor hair coat of a parasite-ridden horse.

5) Your horse is on other medications including antibacterials and antimicrobials. These alter the good gut bacteria which in turn decreases the absorption of amino acids. In addition, the causes for which these drugs are being used are also increasing the consumption of proteins.

6) Your horse is starving either because there is no food available or he is being fed in a carbohydrate-dependent fashion. The body now has no choice but to consume existing muscle along the top line or, in horses over 30 years, from the cheek muscles. The result is a poor topline, a horse that looks old, sway-back or if still working, kissing spine injuries from back muscles unable to support the spine in ridden and athletic endeavors.


Proteins are essential but are often overlooked by horse owners because they seem “too complicated” to understand. They are not. Simply feed your horse like a horse by allowing it to graze on a variety of pastures.

  1. If no pasture or poor pasture or pasture made of only 1 type of grass is available, add plenty of grass hay plus some legume hay. If all looks good and the horse is not being used, then add about ½ pound of a grain-free protein supplement per day for a 1000 to 1400-pound horse.
  2. If working or if you believe there is a protein deficiency, add 1 pound of a grain-free protein supplement (soy and whey mix) per 1000 to 1400 pound horse per day. When the horse looks great (hair coat, top line, hooves, lameness, disease) then reduce the amount being fed by ½.
  3. Eliminate sugars from the grain, byproducts, treats, and fruit (unless in season and available where you live). If you can’t find a protein supplement without grain, use one that has only 1 grain and watch for signs of grain intolerance.

There – you now know about the importance of protein and realize that most horses kept by humans are slightly to severely deficient in protein. Couple this with what you have already learned and then join me for the next blog.

Back to top


Remember, you can also start a discussion in the forums for a more in-depth experience!

This site uses Akismet to reduce spam. Learn how your comment data is processed.

    1. Desiree – Soybean meal (SBM) has all the essential amino acids (EAA’s) and has a bioavailability of 80%.

      According to, in 100g of SBM there are 49g of protein, 36g carbs and 2.5g fat and 337 calories. Coconut meal or meat (what you are calling “Copra”) is 3g protein, 15g carbs and 34g fat and 354 calories.

      Coconut meal is a great source of non-inflammatory fat and is a good way to add weight in fat to horses, especially old horses having trouble maintaining their condition. But it is NOT a good protein source and is NOT a substitute for SBM.

      1. Thank you, Dr Tucker, for the explanation. I have voraciously consumed so much of this information here over the past three days, what a gift to us all (and then everyone we pass it along to)! My horses have been grain-free for ~9 yrs but I’ve seen a gradual decline in the topline of the 19 yo OTTB. I thought it was age. Since, according to CoolStance, copra has 20% protein (, I always thought I was providing a good source for the past 8 yrs. Now I see the differences in EAAs. My new 3 yo (just turned) has lost a lot of topline in just a few months of ownership, so that’s what led me to finally discovering your blog. The day after I read it all night, I picked up SBM and organic alfalfa pellets, and started the journey. I can’t wait to share outcomes!

  1. What is the name of a company that sells the soybean meal online?….i can not find it anywhere around middle TN?

    1. I know they will ship SBM but you will need to buy 1000 pounds or more or the shipping will bee expensive. Google searches will help you find someone.

      Please join the Facebook private group called “The Horse’s Advocate” for 1) a faster response time and 2) advice from others who have found it hard to find SBM in their areas.

      1. Only have 2 horses. So 1000lbs of SBM wouldn’t work….i did join the horses advocate and have read every blog there is some twice…

  2. How much protein or what percentage is bioavailable from grains. (I don’t personally consider grain as a protein source, Ohhh I need protein, lets eat bread and pasta, ha ha-nope) I assume it is lower than 50%

    1. I am not sure of the bioavailability of protein from grains. But the important thing to note about grains is that they cause gut inflammation and is behind the chronic protein deficiency in horses. Therefore I am not sure if the proteins in these plant d=seeds ever make it into the horses’ body. Good question but remember, the bioavailability of protein is measured in a healthy gut, not in an inflamed gut.

  3. Doc T, Melissa Buday was at my barn last week doing teeth on my almost 9 year old OTTB 17-3 HH. I really enjoy meeting her and watching her horsemanship and the way she dealt with Royale my hat goes of to her!
    Melissa mentioned the no grain inflammatory approach to consider for royale’s diet. I was curious to learn more about it, at the end of her visit she left a nice gift package I found very thoughtful and informative. Within this package there was lots of great information and especially an article “special issue on nutrition” that explained in a very simple way why chronic protein deficiency in horses is so prevalent today. I am practicing everything your article claims not to do and Royale being a hard keeper and our misconception that adding more protein can only help. I keep adding more of the wrong kind of protein. I am taking the challenge and we are eliminating grain and go hay! hay! hay! and maybe some alfalfa cubes for breakfast with the cool stance I currently feed. I am Cancelling, cool calories, msm, beet pulp w molasses and the four scoops of sweet feed and pellet feed, I feed him 2 in the am and 2 in the pm. He has always been in good quality T&A or O&A hay. I also mix soy oil on his feed four pumps ( should I suspend?) However, what soy bean meal amount should I feed if I can find it? Should I mix with the cubes? How much of the Pro Add Ultimate without corn should I feed?
    Thank you for your research and sharing your experience, makes sense.

    Walter M

    1. Thanks Walter for thanking us for the reading material. My wife put a lot of effort into creating and packaging those and believe it or not, you are the first to write a thank you note. She and I appreciate it.

      I am glad you are trying the no-grain challenge. However, the soy oil is also inflammatory (at least for humans) so you should stop this as well.

      Get de-hulled soybean meal with either pressed or chemically extracted oil. Either way does not affect the horse’s gut. This comes in many protein supplements including ProAdd Ultimate (Progressive Nutrition / Nutrena). If you feed ProAdd then you do NOT need to add soybean meal. ProoAdd can be mixed with the hay cubes or fed on its own. Horses love it (a pellet).

      Thanks for your kind words about Melissa. I passed them on to her. Doc T

  4. Hi Doc T, I did add soy and whey protein (75:25) to Tap’s food. It has only been a week. His topline is gone and his coat is showing signs of deficiency. The rest of the food is bermuda hay and alfalfa pellets. Thanks for all your help. Lynne

  5. Given the Plant Paradox and that diary animals produced that which they eat, lectin-heavy milk, you still recommend whey? Why? Has the lectins been removed from the whey during cheese-making? I also questioned Dr. Gundry’s logic when he indicates whey as safe to eat. Do you know why it is safe from lectins? Thanks.

    1. From Wikipedia: “Whey protein is the collection of globular proteins isolated from whey. The protein in cow’s milk is 20% whey protein and 80% casein protein”

      The lectin in milk from B&W Holsteins is in the casein part derived from a gene mutation. There are no known lectins in the whey portion.

  6. Really interesting series (think I have missed a couple). When you say a grain free protein supplement, do you mean something like lupins? Mung beans, chic peas, faba beans? I have taken my horses off soy products for over 6 months, because of the possibility of being GMO modified & also being more inflammatory (compared to something with omega 3’s in it). Lately the horses are being fed lucerne (alfalfa) in the morning & grassy lucerne at night, with grass all day (we’ve had a good season) :). I went off any manufactured feeds because many of them were high in iron & apparently where we are in Australia, it’s not needed. So i started on copra meal, a little rice bran & then started adding lupins. I also ground up linseed &french millet seed, then added a mix of herbs etc (turmeric, chamomile, brewers yeast, Dolomite , ginger, celery seed, seaweed meal etc). Not sure whether that’s on the right track or not. 🙂 Thanks for your info. Cheers Andrea 🙂 (Qld, Australia)

    1. Thanks for reading these blogs!

      All foods are genetically modified – even the grass planted in the field. Soy was the first to be modified for glyphosate but there have been no known diseases in horses attributed directly to GM food of any kind. It is a good debate if GM foods affect the gut microbes.

      This said, when you feed a variety of protein sources you will be supplying a broad spectrum of the limiting amino acids. Remember that if you are low in just one essential amino acid, you will be low in all the proteins that AA makes. So the more the merrier until the horse has reestablished the proteins needed every day. Then the recycling program will work with little more exogenous protein added.

      Also legumes such as soy are OK for horses but not for humans. The short chain fatty acids derived from cellulose keeps things happy. The Omega 3 v 6 debate rages in the human world but I am not sure about the hind gut fermenter. Remember that the human and the horse differ greatly when looking at the raw materials and their conversion into fuel within the gut. However, everything after the absorption of these fuels is the same. Placing raw materials into a horse that should not be there will cause inflammation. Soy bean meal so far doesn’t seem to have an inflammatory effect on the gut lining. I do not know about the other protein sources you mentioned. I am suggesting to avoid any bran or soft seeds due to the lectins (coming up in another blog). I believe their inflammatory effect on the gut wall in many horses is worse than any GM food. In fact, in the debate about GM food and pesticides and fertilizers, the effect of lectins is missing yet very relevant. By feeding horses just the things they normally find on the ground and supplementing for a year or two with extra protein (soy, whey) appears to be helping so many horses without any side effects. Keep it simple. Feed a horse with the things it would find in the field at the time of year it’s grazing. If needed, add non-inflammatory things that act like a pre-biotic (food for the gut microbes). This might include coconut meal which I think you call copra meal.

      Changing beliefs isn’t easy but if what you are doing isn’t working, at least these blogs will open up other avenues for thought of what might.

  7. Interesting article. Do you recommend any foods/supplements, etc.. for a horse with chronic Lyme disease? I’ve tried almost everything. Thanks for any help.

    1. This is between you and your vet. But the theme of what I am offering in these blogs is this: It is NOT the addition of things to the horse’s diet but IS the removal of things including “foods and supplements” that don’t belong in the guts and may be causing inflammation. It is the paradigm that we need a quick fix by adding something missing in the diet when it really is that we need to remove the causes of inflammation and allow the gut microbes to re-establish themselves to make the horse healthy.

      In other words – we give the horse raw materials that feed the gut microbes. They in turn produce the fuels that feed the mitochondria. They in turn provide the energy for the horse to survive and thrive. Adding raw materials that kill or change the gut microbes or that cause leakage of foreign things into the horse bypassing the defense mechanism is what causes the horse to become unthrifty, ill, lame, misbehave and in general, not live at a peak level. Best thing is that in feeding a horse like a horse (not a human, dog, goat, pig or other animal) it actually becomes less expensive.

    1. Exactly – there is no research. But there is evidence that SOMETHING isn’t working. This idea that there is a chronic protein deficiency from mitochondrial fatigue due to daily carbohydrate dependency is certainly worth looking into.

      There was plenty of evidence that the sun circled the Earth. Until someone asked simple questions about length of day and change of seasons. To me, it has become obvious that horses are breaking down in connective tissue and in health. And the research isn’t looking at history or the simple solutions. People who have tried eliminating inflammation from grain and byproducts and supplementing with protein have seen improvement in so many categories. But it is still too early to tell if it solves everything. But all that is being done today is not curing or improving the health of horses.

      It is the job of someone smarter than me to do the research (without an agenda or the support of the industry). In the meantime, frustrated horse owners are trying this and finding improvements in many different areas. All without spending money on a supplement or a service, but all based on what is now known in science. Basically – sugar fed throughout the year to horses will add fat at the expense of protein (muscle and other sources). Removing or reducing glucose at least during part of the year will allow the horse to use body fat for fuel without affecting the muscles of the top line and other protein sources.

      Rachael – will you be the one to do the research? Or do you know of someone?