But there are no official studies to prove or disprove the benefits of Diatomaceous Earth. As it can not be patented the likelihood of funding for double-blind studies is little to zero. Popular for years earlier as a natural product in keeping mites down in chicken coops, it was also used externally as a ´dust´ for chickens, dogs and cats, against fleas.
Diatoms are microscopic algae with skeletons made of silica (chemically like sand!). The hollow silica shell of DE absorbs the moisture from insects, which is probably why it works well as an external anti-parasite. Dusted into the dry skin of an animal the only moisture it will find is that of the unwanted beasties. Internally the shell is going to engorge itself with any liquid it ´bumps´ into. As such it possibly has an indirect effect as it cleans the lining of the intestines and colon of built up gunk! Though it´s use as a wormer would appear negligible**.
Doing our best to manage our horses as naturally as possible, of course I was interested in the possibilities of an all natural wormer. Having 11 horses of my own, plus those of clients, the cost effectiveness was also a big seller! But I needed assurance, not just a nicely written article by a most affable person, that it would work.
Our horses live out 24/7 in various herds, dependent on personalities and if we are breeding our stallion or not (yes, he also lives out in a herd). Their paddocks are not only cleared of manure, they are also rotated, leaving them fallow for 2 or 3 months at a time when we can. Worm counts are done with seasonal changes twice a year and at the time of deciding to do some trials with DE all our horses were returning results of <50 EPG (Eggs per gram), which was actually a ´no eggs recorded in both counts´ - as the lab that does our counts always checks twice. So, along with their low starch diet, with 24/7 ad-lib hay and clean paddocks, our horses were not going to provide any interesting or different results.
Luck (!) would have it that my husband decided to indulge himself with a new horse at the same time as 2 new liveries arrived, so, along with the 2 horses of a neighbour who also live out, but I know have never been wormed and their paddock is never cleaned, I was able to cobble a trial together.
Over a 3 month period I gave 3 groups of horses varying amounts of DE. Worm tests were completed before we started, after one month, and again at the end of the 3 months. These are the results;
Group 1 - Our own horses, free of worms. Turned out in a paddock occupied for one month by the new liveries, when we decided to do the trial we didn´t clean the paddock for the last 2 weeks before swapping the herds over. It killed us not to, but our thinking was that they may pick up some worms and if DE does work their count may increase - if we got the timing right for the count! It was the only way I could think of performing a reverse test! After one week being in their new (dirty) paddock we started cleaning again.
Group 2 - New liveries + One (the new boy). Turned out in clean paddock, kept clean. We gave them the highest dosage of DE, figuring they had the least worms of the two groups with worms, and this would give the DE a fighting chance to work. My skepticism decided the 3rd group, with far higher counts, though not usual (I don´t know many people who keep their horses in such rather dismal condition) would need serious intervention to reduce their worm count, but, see*.
Group 3 - Neighbour horses. Turned out in a clean paddock, kept clean. The horse with the highest count was dosed at 100g daily of DE. The results are in the chart.
I have not published my results before, because they are not scientific, they are not sufficiently extensive to confirm or dispel, they should not sway anyone either way in regard to Diatomaceous Earth. I carried them out for my own curiosity. But there are so many anecdotes available now I thought I´d add some fuel to the debates. You can draw your own conclusions.
We do now worm our horses naturally, using a ´recipe´ I devised and honed (using the neighbours horses as the guinea pigs!) of a mix of various plants known for their parasite killing properties . Again, I did counts along the way to assure it worked. Students who complete Level 2 of our WHP courses get to share the recipe. Just like DE, being all natural, it can do no harm even if it does no good! But the neighbours equines were worm free nearly 4 months after the DE trial finished and having then given them 3 courses (a dose a day for 5 days once every 4th week) of my home brew. The 3 new horses at our yard counted <50 3 months later as well.
**Of course, if you keep your paddocks regularly poop-picked, feed your horse a low starch and sugar diet, scarify, harrow or rotate paddocks from time to time and regularly clean water troughs (using ACV or goldfish is a great way to keep them cleaner longer!) worms should not be a worry and along with the extra protection of DE all is well. But please do remember tapeworms are a whole different beastie to bot/round/red etc, requiring special testing or blood tests.