How to Deworm Horses

Knowing how to deworm your horses is absolutely essential to their well-being. If your horse has a parasite burden, he will be more susceptible to illness and weight loss, and overall just won’t be as healthy as he could be. The good news is that deworming and keeping your horses from having a parasite burden is simple and inexpensive. Simply feed your horses Diatomaceous Earth (DE) every day all year-round.

DE is an absolute staple in our approach to caring for horses – mainly for deworming but also for its many other benefits. It is an effective, all-natural, non-toxic way to deworm horses, detox them of heavy metals and toxins, and provides them with 15 trace minerals. DE is about 84% silica which is essential for healthy skin, coat, mane and tail, hooves, bones, and teeth.

What is DE and how does it work to deworm horses?

DE is the fossilized remains of microscopic one-celled plants (phytoplankton) called diatoms. It is powdery in texture. When DE is looked at through a microscope, it looks like honeycombs or filters with holes throughout the sides. When taken internally DE works in a mechanical/physical manner (not chemically) to rid the body of bacteria, heavy metals, pesticides and parasites. DE doesn’t flush all the parasites out at one time. Instead, it works slowly to eliminate the full life cycle of the parasites (certain parasites take longer to get rid of).

Chemical dewormers, on the other hand, can cause a huge die off of parasites quickly, which is very stressful on the body and puts the horse at risk of impaction colic and illness!

Parasites cannot build up resistance to DE because, again, DE works in a mechanical/physical manner to kill the parasites. Parasites have definitely built resistance to chemical dewormers. So, on top of the fact that chemical dewormers are terrible for your horses’ health (and unsafe for you) they aren’t even a guarantee to work! After reading about the risks of chemical dewormers (horses becoming very sick and even dying), we wanted to find a safe, natural, non-toxic way to deworm our horses. Nor did we want to expose ourselves to those poisonous chemicals in the process! Diatomaceous earth ticks all of those boxes! It is an effective, low-cost supplement that has no negatives, only benefits.

We’ve never had a horse turn his nose up at feed with DE on it, but they sure don’t want to take the chemical dewormers! So, that’s a huge plus of using DE for deworming – no fighting with your horse to get it in them!

Which DE to feed:

The most pure and effective form of DE will be off-white in color. If it is brownish or grayish that means it contains more clay, which isn’t ideal.

We buy diatomaceous earth by the brand PERMA-GUARD from a local farm store. It costs about $25 per 50-pound bag.


DE is not a chemical, so it is not toxic, however, when using DE, it is VERY IMPORTANT that you ONLY EVER use FOOD GRADE diatomaceous earth. Any DE other than food grade could poison and possibly kill your horse as it has a toxic chemical added to it! NEVER use pool filter grade, it is TOXIC!!

How to feed DE:

For the best results, you need to feed your horses DE every day all year-round, which is what we do and recommend. This is because horses constantly come in contact with parasites, heavy metals, toxins, etc. in the environment and by keeping DE in their systems every day all year-round these things are kept at a bare minimum in their bodies, which will result in better overall health. Since DE is quite powdery you need to wet it down on your horses’ feed. It would be rather unpleasant for a horse to start eating and DE puffs into their face, causing them to inhale it. Since we supplement our horses with soaked alfalfa pellets and mix the DE into that, this isn’t an issue.

The ratios for feeding DE:

For horses around 1,000 pounds, feed 1 to 2 cups DE per day. For larger horses you will need to increase the amount and for smaller horses or ponies you may choose to decrease the amount. If you know your horse has a parasite infestation or are concerned that he may, feed double the maintenance amount daily for a minimum of 90 days (to ensure you get the full life cycle of the parasites). As a matter of fact, when first starting a horse on DE, feed double the daily maintenance amount for a minimum of 90 days whether you think they have a parasite load or not, to be on the safe side.

Then you can go back to the daily maintenance amount.

It’s best to err on the side of feeding more than necessary because for DE to work effectively you must feed enough.

This is because DE must come in contact with the parasites to kill them. You will not harm your horse by “over-feeding” DE. If you are under the impression that diatomaceous earth doesn’t work or have heard it doesn’t work that is likely coming from someone who didn’t feed enough of it.

We feed our Quarter horses (Star and Pete) 1.5 to 2 cups each per day and Shetland pony (Duke) 1/2 to 1 cup per day.

How to tell if your horses have parasites:

Fecal egg tests are only 20-25% accurate so we don’t suggest that for determining if your horses have a parasite load. With a low accuracy rate, it’s just not a good use of your money. Instead, we suggest going off how your horses look and are acting/feeling, which is what we do.

Here is a list of telltale signs that your horse has a parasite load:

  • Pot Belly
  • Dull coat
  • Dull eyes
  • Worms visible in manure
  • Winter coat doesn’t shed out well
  • Skinny/can’t keep weight on
  • Illness/infections
  • Lethargy

Signs your horse doesn’t have a parasite load:

  • No pot belly
  • Gleaming coat all year-round
  • Clear/shiny eyes
  • No visible worms in manure
  • Winter coat sheds out beautifully
  • Not skinny
  • Illness/infections very rare
  • Energetic/playful

To summarize, here is a list of benefits from feeding DE year-round:

  • Natural, effective, non-toxic dewormer
  • Healthier, shiny coats (we attribute our horses’ gleaming coats in large part to DE)
  • Stronger hooves
  • Mane and tail growth
  • Less flies
  • Contains 15 trace minerals
  • Helps detox the body of bacteria, heavy metals, pesticides, and even viruses
  • Reduces stress (less heavy metals, toxins, parasites, etc. equals less stress on the body)
  • Helps horses maintain healthy weights (by aiding the body in absorbing nutrients from food and reducing the toxic load on the body)
  • Digestive aid
  • Reduces manure and urine odor (BIG TIME)
  • Cost effective (BIG TIME – as you can see you get a lot of bang for your buck with DE)
  • Better overall health

We have been feeding diatomaceous earth for many years now, with great success, and can’t recommend it more!

We encourage you to read these two articles as well, if you’d like to learn even more about DE: and

You’ll read amazing examples of how effective DE is!

We hope this article has left you well informed about how to deworm horses.

We also have a YouTube video on deworming horses:

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