Whether or not to use food grade diatomaceous earth (DE) in one's flock is a decision each chicken-keeper must make for themselves. As a new chicken-keeper, I read quite a lot about DE before purchasing a ten pound bag, thinking that the claimed benefits sounded tremendous, but I wondered whether it was possible for a product that claimed to fix so many problems in humans and animals could be the real deal. I had also read reports of the carcinogenic effects on humans breathing DE and the package warnings to wear a respirator when using it, both of which scared the daylights out of me.
Members of my flock, enjoying a nice, communal dust bath.
As a lawyer, when reading about the benefits of any product, a red flag always goes up in my mind when I read product label claims prefaced by "may, might or could," particularly when written by a company selling the product. For example: "...the addition of (DE) to chicken feed MAY also provide additional benefits including increased body weight, egg production and egg quality as well as decreased internal parasites (in poultry with a lower natural resistance)." Okay, it may. But it may not. Who knows? Not I.
Whenever I have technical or scientific questions, I defer to known, respected, qualifed experts for guidance. In deciding whether to use DE in/around/with/on/near my backyard chickens, I looked to two highly qualified, experienced and educated professionals in the chicken-keeping world for their opinions about the claimed benefits and any dangers of food grade diatomaceous earth: Gail Damerow and Dr. Mike Petrik, DVM, MSc, a practicing chicken veterinarian.
According to Gail Damerow in The Chicken Encyclopedia, adding diatomaceous earth, wood ashes or lime-and-sulfur garden powder to their dust bath is hazardous to their respiratory health and should be avoided unless they are "seriously infested" with parasites. Even in that case, she writes, "the benefit may outweigh the danger of TEMPORARILY adding such materials." (p. 93 emphasis added)
Damerow also states: "Diatomaceous earth is also sometimes fed to chickens as a dewormer, which supposedly causes dehydration and death to internal parasites. But when combined with a chicken's saliva, diatomaceous earth softens and loses its cutting edge. The only way it could dehydrate internal parasites would be if it contained a hydrophilic substance that draws moisture from a parasite's body, and such a substance would equally affect the chicken's innards. On the other hand, diatomaceous earth contains a lot of trace minerals that are beneficial to chickens, even if it does not act as a dewormer." (p. 84)
Dr. Mike Petrik, DVM, MSc, aka: The Chicken Vet, for his thoughts on the subject. He is a practicing veterinarian who works with professional farmers and has overseen the care of millions of laying hens in his decade+ of practice. What follows is his written response.
The theory is that DE is dehydrating because of the sand content, and because the algae are microscopically jagged, they scratch the waxy coating on parasites, allowing them to be killed by dehydrating the worm, tick, cocci or flea. It is touted as a "natural" worming medication and external parasite medication. What you need to realize is that the gut is full of water (making it very hard to dehydrate anything), and that it takes a long exposure time to kill multicellular (ie ticks and mites) parasites.
I'm also a little leery of any product that claims to do everything....diatomaceous earth claims to be useful in animals, on animals, in the walls of barns, coops and houses, as a pasture treatment, in the yard and garden, and as a treatment for granaries. DE kills bacteria, viruses, absorbs and neutralizes mercury, eliminates drug residues, absorbs organophosphate pesticides, etc, etc. Really? To be honest, all the scientific literature is very equivocal on the usefulness. Some studies find "trends", but very little statistical significance, some studies say that DE is poorly effective at a relative humidity above 85%. One study showed more parasites in one breed of hen fed DE, and less parasites in another breed of hen fed DE.
At the end of the day, my feeling is that, if you want to treat the parasites in your flock, use a treatment that works....has been designed to work, and has been proven to work. A well-conceived parasite program that uses different classes of drugs, observes withdrawal times, and will effectively control parasites as well as resistance.
I don't believe that there is much risk in using DE in your hens, but I am afraid that you may believe that you are controlling parasites when, in fact, you are mostly feeding sand. I apologize to any "anti-drug" advocates that may be offended by my stance in this regard, but I have seen too many instances of treatments that served only to allow animals to suffer infections until regular treatments are finally commenced."
Dr. Mike Petrik, DVM, MSc,
The Chicken Vet