Protein in Horse Feed & Hay

Newly born, Ella takes in her worldHorses of all ages require adequate amounts of protein for maintenance, growth, reproduction and work, with growth and reproduction being the most critical time periods.  Proteins are important building blocks for body cells.  Feed intake, growth, physical activity, physical endurance, condition, production of milk and fetal development can all be impaired if protein intake is inadequate.

Most every horse owner can name the protein level of the feed they are currently using.  “A 12% sweet feed” is a common answer when asked that question – but how important is that protein percentage?  While the total protein in the horses’ diet is important, horses actually require essential amino acids, even though crude protein is what is required by law to be listed in a guaranteed analysis.  Many feed manufacturers are moving towards listing the amino acids on the tag, which can help horse owners to see the quality of the protein sources being used.

Beyond the grain portion of the diet, a major factor to watch for regarding protein in an equine diet is the hay source.  After all, hay makes up the majority of the diet, and thus a lot of the protein in the diet comes from the hay. Horse owners need to figure in what their hay sources are providing, and balance it together with their grain source, to determine what their horses are consuming.

Listed below are protein percentages required by the major categories of horses – please note that these are for the TOTAL DIET, not just the grain portion.

  • Foals: 16-18%
  • Weanlings: 14-16%
  • Yearlings: 12-14%
  • Mature horses: 10-12%
  • Lactating mares: 12-14%

In order to figure out the total protein in your horses’ diet, follow this simple calculation:

( (Lbs Hay x Protein in Hay) + (Lbs Grain x Protein in Grain) ) / Total Lbs Fed = Protein in Total Diet

To have an accurate estimate of protein in your hay, it is best to have it tested.  Check with your local extension office or feed store for labs in your area that will do the testing.  Hay protein can vary dramatically from one cutting to the next, and from one field to the next.  Rainfall, stage of growth when harvested, and a variety of other factors can also influence the quality of the hay.  Alfalfa hays are typically considered to be higher protein that timothy or other grass hays, however if alfalfa is harvested late, perhaps due to weather concerns that make it tough to get in the field, it can have lower proteins than some grass hays that are harvested at the proper time.  Thus, it is always a good idea to know the facts behind your hay source rather than “guesstimating”.

A final point that must be made about protein:  Increased protein levels are not generally responsible for a “hot” horse.  Protein is a very inefficient source of energy, and its main use in a mature horse is the re-building of muscle and other body cells after exercise.  Instead, it is the starch and sugars in a horses diet, as well as the calorie intake to calories used (exercise level) ratio, that are primarily responsible for a “hot” horse.  But that’s a topic for another blog post!

23 Replies to “Protein in Horse Feed & Hay”

  1. We have always been told that crushed peanut hulls, used in some horse feeds, are not digestable. NOW, we have a vet telling people that is not true. Please help us clarify this issue.

    1. Hello Evelyn,
      Thank you for your question.

      Peanut hulls are a useful ingredient in that they provide a high level of fiber and can be used to provide dry matter intake while providing a limited amount of Digestible Energy (DE). They are not indigestible, they are just not highly digestible.

      Peanut hulls are not highly digestible because they have a high level of lignin (which is why they are a rigid shell that protects the peanut inside quite well) and as a result they have a fairly low DE value if about 570 Calories per lb, compared to oat hulls at 780 Calories/lb or soy hulls at 850 Calories/lb, all per the 1989 NRC for Horses, 5th Edition.

      The bigger concern generally with peanut hulls is that they also do require monitoring as they are grown in the ground and, depending on moisture and growing conditions, have a risk of mycotoxin contamination. On the other hand, prime alfalfa has a risk of blister beetle contamination, so nothing is risk free. You just need to ensure that the feed company utilizing them has strict quality control and ingredient testing measures in place.

      As an example to help clarify, using peanut hulls is similar to you or I eating celery. Low in calories, but good for fiber.

      Thank you ~ Roy J.

  2. I know someone who has a horse & it hasnt had hay for about three weeks! Is that right? They said it is fine because it eats the under brush. We live in the woods, which means there isnt much grass and there is no pasture. Please let me know, for I worry for that horse. Thank you for any help.
    Sincerely Dawn Milligan

    1. Hi Dawn, Thank you for keeping on eye on your neighbor’s horse. You need to work with local authorities to report neglect. If you aren’t sure how to contact your local animal control, start with your local vet – they should be able to direct you to resources in your area.
      Thank you again for your concern!
      Gina T.

  3. I have an old horse that is thin. She gets hay, forage and a 16% pelleted grain for mature horses. She also gets a “weight gainer” supplement. We live in the upper mid-west so she burns a lot of calories just staying warm, I would guess. Am I feeding her correctly. She also has a 3 sided pole barn for housing.

    1. Hello Cindy, Thanks for checking in with us. For your mare, keep pushing the hay/forage at her, as much as she will consume. If you haven’t, it’s always a good idea to have her teeth checked out and floated if need be, to keep her chewing properly.

      In regards to feed, she likely does not need a 16% protein grain. And for upping her calorie intake, you actually want to look at the fat level of the feed. Check the tag on the product you are giving her today – if it’s only a 3% or so fat (that is the amount naturally occuring in grains) then we’d suggest moving to a feed with a 6 or 7% fat level, or higher. Then, make sure you are feeding the product according to the directions for her bodyweight and activity level – if you want her to gain weight, it would be good to feed her for one activity level higher than what she is actually at, until she gains the weight she needs.

      It also might be time to move her to a Senior horse feed – higher fat, more easily digestible protein sources, and vitamin/mineral levels designed for an aging horse – to help get her on track and keep her going strong through the coming winter.

      Hope that helps – please do let us know if you have more questions. Thanks ~ Gina T.

  4. Hi Gina T I like your answers and have a concern there are 2 standardbred race horses in the bar that are not getting any hay nor turn out the trainer feds hay cubes and grains they jog & train on a 1/2 mile track with some days off he believes that the hay cubes contain 2 & 1/2 bales per bag … I say No … his concern is getting more protein & fats into both of these horses one races currently, the other does not as it is not ready, per se I have a TB (thoroughbred, gently raced last year b4 I got her from a track I fed here hay, 4 flakes a day, oats, 1 chopped up apple 3 times a day & 1 chopped up carrot, 3 times a day and I mix water in to soup all this up … as well as I am a firm believer in turn & forage she is in great shape and I will begin to re-school her once the summer heat & bugs slow down

    I look forward to any input your have & thank you, in advance, for your time

    kind regards,


    1. Hi Randy Kay, Thanks for checking in with us! Great questions. For the horses with the trainer that are being hay cubes – while not ideal to be on a diet of hay cubes and grain, it certainly is an option. There are horses out there who have to be on this type of diet, for a variety of reasons including heaves, allergies, or an inability to chew long-stemmed roughage due to dental issues. The cubes are often soaked in water for these groups of horses, to aid in chewing. Generally we would recommend a horse to be receiving at least some long-stemmed roughage if at all possible, for overall digestive health and also to reduce boredom and possible unwanted behaviors out of that boredom. Either way, the key is to ensure that the horse is receiving enough pounds of roughage to maintain health – a good guideline is 1.5 – 2 % of bodyweight. So, for a 1000 lb horse, they should receive 15-20 pounds per day. Add in a grain source for some additional calories, and a horse can maintain just fine on the cubes & grain.

      For your horse, we would encourage you to weigh the flakes you are feeding, just to ensure she is also receiving that 1.5 – 2.0 % per day in roughage. If she is maintaining her weight well, then you are probably on the right track. If she is going in to work though, you might consider something other than oats to provide a more balanced nutrient profile for her – oats are an “okay” source of protein, but have an inverted calcium to phosphorus ratio (you don’t want that, for any animal), and provide some minimal vitamins & minerals. A couple suggestions for her, depending on how many pounds of oats per day you are providing her, would be either Empower Balance if you are only feeding a couple pounds per day, or SafeChoice Original if you are feeding in the 3-7 pounds per day range.

      Hope this helps! If you have more questions, please let us know. Thanks ~ Gina T.

  5. Hi Gina thank you for getting back to me I use 2.5% of body weight she gets an apple & carrots at every meal, so 3 times a day … that should provide vitamins, along with oats 3 times a day I have a mineral block in her stall too I turn her out, so she forages/grazes as well as she gets hay cubes too I think she has a balanced diet so far as her work load increases I will provide other feeds … sweet feeds etc etc again, thank you very much for your time cya now GOD Bless … Randy

    1. Hi Randy Kay, We would caution you in relying on apples & carrots for providing adequate vitamins for your horse. Unfortunately, “an apple a day” probably doesn’t apply to a 1200 lb horse! If you want to provide adequate vitamins and minerals, we would encourage you to look at a supplement or feed specifically designed to do that in a proper manner for horses.
      Thanks ~ Gina T.

  6. Good Morning Tina she gets 3-4 apples a day & 3-4 carrots every day … she is not 1200 pounds I also have a free choice mineral block in her stall from time to time she gets sweet feed & ‘xplosion’ feed our vet & farrier are impressed with her body condition & her overall health & demeanor I provided her with time to help her grow front feet (horn) … I am also an equine podiatrist take care GOD Bless … cya … Randy

  7. I think it is cool that you can calculate the protein in your horse yourself. so cool!

  8. I have standardbred race horses. Can you feed to much protein in the summer time?

    1. Hello Bo, Thank you for the question. If you are working the horses, and feeding a typical horse feed at the suggested feeding rate and hay, the protein intake will be just fine.
      Thank you ~ Gina T.

  9. My polocrosse pony has heat spots/protein spots or whatever else you can call them on his back. I’ve just put him out in the paddock for a spell. Been told to cut out protein from his diet. Hard if he’s in work getting hard fed and hay. Its good quality hay. He gets nothing ‘hot’ no oat feed.

    1. Hello Velia,
      It sounds like you are referring to what are often called protein bumps. These are not caused by too much protein in the diet, but often a allergic reaction to a certain protein source. Did you recently change pastures, hay supply, grain or supplements? You mentioned you don’t feed oats, but barley, beet pulp, clover and even bran have been none to cause allergic reactions.

      If none of the above have changes in your horses diet recently, you may have to eliminate certain items in the horses diet one at a time, until you can determine the cause.

      I would also suggest contacting your veterinarian, for advice on what treatment should be administered to your horse such as a corticosteroid.

      Thank you ~ Gina T.

  10. Hi I have a 14 yr old gelding that was a low maintenance type, never needed grain to hold a very healthy to almost a bit over weight. Over the past ten months he has dropped probably 300 pounds, mostly muscle mass. We have have a slew of test done on him, worming of all types, teeth floated, hay tested, blood tests, x-rays, everything short of an MRI. His attitude is actually quite alert and he eats very readily. He gets about 30 lbs of hay a day and usually eats it all, plus 6 pounds of a 14% protein, 8% fat senior feed. He is barely holding steady and so far not seeming to lose any more weight, but after feeding this amount for 5 months there has been no improvement beyond not losing more weight so far. Is there something I am missing? Vet is getting frustrated at cause of weight loss and I am too. What more can I do for this horse?

    1. Hi Tina,
      It would be really useful to have information regarding hay test analysis. If the protein (actually essential amino acid) content of the hay is low and not readily digestible, it is very possible that your horse is not getting essential amino acid intake to maintain muscle mass. The first 3 essential amino acids are lysine, methionine and threonine. If the hay is marginal, your horse may benefit from additional high quality protein, perhaps from either higher feeding rate on the senior feed, assuming it is a product with guaranteed amino acid content, or the addition of a higher protein balancer product as well. Also, would be useful to know the target weight for your horse.

      Best wishes,

  11. what percent of an appaloosa’s diet should consist of hay? Do you know what percent of grass, grain, and all that other stuff, how much of it are they supposed to eat?
    A Friend

    1. Hi Friend,

      Thank you for your question about your Appaloosa’s diet. This may vary quite a bit depending on what your horse does for a living!
      We normally feed about 1.5-1.75% of a horse’s bodyweight in forage or pasture equivalent. For a 1000 pound horse, that would be 15-17.5 pounds per head per day. If your horse is not doing much work, we might add a forage balance product at 1-2 pounds per head per day to provide additional amino acids, vitamins and minerals. Salt should be available free choice and fresh clean water should be available at all times. If your Appaloosa is being worked regularly, you would need to add a grain based feed to provide the extra Calories to maintain body condition and perhaps feed less of the balancer product.
      Best of luck!

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