What the Hay? A Lesson in Nutrition: Part 1

What the Hay? A Lesson in Nutrition: Part 1


Did you know that your horse has the inability to vomit? This was a totally new thought for me as I sat in the lecture for “Healthy Happy Horse” at Texas A&M listening to Dr. Josie Coverdale, a Professor in Animal Science. The horse digestive system is a strict one-way flow: Mouth→ Esophagus → Stomach → Small Intestine →Hind Gut → Caecum → Large Colon → Small Colon → Exit.  Once it's swallowed, it's in, which is why colic can be such an issue.  If you are really curious about how all of this digestive stuff works, I found this 10 minute sciency video that explains with diagrams the tract that food takes in your horse. It's very interesting and Dr. Teitzel has an Australian accent, which I think adds to the overall quality of the video.

So this raises an important question: what do you feed your horse?  I'm not an equine nutritionist, but I have always tried to provide the best forage and grain supplement for my horses.  It is important to remember that, just like humans, horses tend to function best with small frequent meals, hence why they prefer to graze all day long. They should be eating a minimum of 1% of their body weight daily and of that 1% at least half (if not more) should be dietary fibers such as hay and forage. Grain is meant to be supplemental and should not be a replacement for forage.  If you’re like me, you’ve heard that stat before and then looked over at your horse cocked your head to the side and asked the very important question, "What do you weigh?"  This question has always brought up the image of the carnival game where some brave contestant is standing before a giant scale and a Carnival Worker is trying to guess the exact number before the scale reveals the true answer.  Ideally you would have a rough idea based on a previous vet visit or by knowing what your horse's general weight should be.  But what if you don't know or you want to be able to monitor your horse's weight closer throughout the changing of the seasons?  Well, I have some math for you that just might help with that question.  Although, not one hundred percent accurate, this equation is able to give you a really, really good estimate of how much your horse weighs.  This number can then allow you to determine how much food you should actually be giving your horse.  As always, please check with your veterinarian before you alter any feeding programs.

Heart Girth measurement
body length measure tailBody Length Measurement



The equation requires some measurements.  Using a soft tape measure you will need to measure the horse's heart girth and the body length of the horse.  For the heart girth you need to start at the top of the withers, wrap around the horse’s high stomach, behind the front legs and back up to the withers. This will give you a heart girth measurement in inches. Then you need the body length measurement. Start at the horses shoulder and measure all the way to just around the corner of the butt, about half way to the tail.  Once you have your measurements you can enter it into the equations.  

  • Adult Horse: (Heart Girth x Heart Girth x Body Length) ÷ 330 = Bodyweight in pounds
  • Yearling: (Heart Girth x Heart Girth x Body Length) ÷ 301 = Bodyweight in pounds
  • Weanling: (Heart Girth x Heart Girth x Body Length) ÷ 280 = Bodyweight in pounds                                                


 If you don’t want to use a calculator, you can also go to this website: and they will do the math for you for an adult horse.

Again, remember that this is an approximate weight measurement and a scale will always be more accurate. It’s a great tool, though. Especially if you start to notice that your horse is changing shape; either in the summer getting bigger, or the winter getting smaller. You can now get a rough estimate and see if you need to re-evaulate the amount you are feeding during different times of the year or as your horse ages. The body conditioning scale has been around for years. What you are hoping to achieve is a Body Conditioning Score of 5 or 6. That being said, many competitive horses may have a different ideal body score based on their specific needs.

Some other things to think about when feeding your horse is it's best to not feed on the ground, since the hay or feed you put on the ground will be wasted by either ambitious hooves or becoming too moist.  It is best to place grain in a bucket and hay/forage in a feeding holder.  If you don't need to provide extra hay because your pasture is sufficient, take a stroll out there and make sure you don't have any Johnson grass, Sorghum grass, or Kleingrass (mainly found on the gulf coast- can cause liver toxicity).  All of these plants can cause toxicity in your horse.  Also keep in mind if you have just come through a strong drought season, it is important to remember that this can affect the make-up of forage. Because the plants are trying to become tougher to sustain themselves during the low rain season, safe grasses can develop high levels of nitrates and prussic acid both of which can cause poison in livestock.  Consider providing forage during those times.

If you are one of the few owners that owns a diabetic horse that needs to watch their sugars, keep in mind that you should not let your horse out to graze during peak hours of the day. Plants have more carbohydrates/sugars due to photosynthesis during the daylight hours. If you want to control sugar levels, try putting your horse out at night to keep down the carbohydrates level. 

Next blog will talk about colic and what you can do to help recognize the serious signs of this digestive distress.  Thanks for reading!

Written by Kara Grimes

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  • Burge Linton
Comments 1
  • Barrett LIttell
    Barrett LIttell

    Great read. For our equine athletes to perform at there best we have to be diligent about there nutrition.

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