I first heard of and used diatomaceous earth (DE) when I was working on a ranch in California. I was intrigued to learn that this white powder, which we were adding to the horses feed, had numerous health benefits, including being a natural wormer. The lady who owned the ranch claimed she hadn’t had any issues with worms for years and owned a large number of horses, all of which received a small cup of DE a day.

So what is DE?

It’s the fossilized remains of algae that have cell walls made of silica. Mined from lakes and oceans, it also contains numerous other valuable minerals, like calcium, magnesium, iron, and sodium, which as a result makes it also a beneficial supplement for hoof and coat condition. It is then processed into Food Grade or Industrial Grade DE. Food grade products are purified and the only type that should be used for human/animal use or consumption. If you were to look at it under a microscope, it might resemble what looks like broken glass, making it a good internal cleanser.

Now you might be thinking – why on Earth would I feed my horse something that looks remotely like broken glass, even under a microscope? It’s this very shape that is supposed to make DE such an effective natural wormer. As the DE passes through the horses system, it can “slice up” worms, acting as a gentle exfoliator for the digestive tract, but it remains incapable of cutting even delicate intestinal lining. It essentially accompanies any worm remains, bad microbes, and other unwanted bacteria out of the body – but leaves the good stuff due to its semi-conductive nature and the way it interacts with substances it encounters.

How much DE you feed should depend on your horse’s weight and worm count. As with anything, a slow introduction to your horse’s feed should be made to avoid rapid detoxification, and be sure to consult your vet on the best way to incorporate DE into your worming programme. I’ve experienced some people feeding DE on a daily basis, and others managing worms successfully on two cups a week – it largely depends on the horse. Again, talking to your vet and taking a worm count will help to create an effective plan.

Worming aside, in my time working in the states I noticed the DE was, incredibly, helping with the fly population. When I’ve been to work in hot countries, flies are usually my biggest bugbear, and we all know they can become an issue here in the UK sometimes. Imagine the issue tripled due to favourable weather conditions abroad and lots of sweaty horses to attract them! This was absolutely not an issue at the ranch in California.

DE is a fantastic natural pesticide, effectively drying out the moist areas where flies would normally choose to breed and lay eggs, and its sharp edges again are excellent shredders of insect exoskeletons, killing them off. When dumping manure after mucking out pens, I’d spread some DE across the top (this had been done after every dump on a regular basis) and voila, not a single fly could be seen around the muck heap. It can even be rubbed into a horse’s coat as a dust to help with external parasites in this way.

So not only does DE appear to be a natural and effective wormer, but also great for drying out wet areas – frequently being used to dry out wet stalls in the US, in addition to manure heaps – reducing external parasites, and is a great natural hoof and coat conditioner. It also has no offensive smell, so horses tend to eat it without noticing and adding a little water is all you need to manage its dustiness if that poses an issue.

Please note: This post should not be used as a substitute for veterinary advice, and any changes made to worming programmes/horse’s diet should not be made without consideration for your horse’s own particular needs, or contacting your appropriate horse care professional if needed. Horses with digestive issues such as ulcers may not be suitable for a worming programme containing DE, so it’s advised you discuss this with your vet before making an introduction.