I was under the impression that food grade actually meant more pure and thus more silica.There are two types of DE--one is Food Grade and the Silica is lower. It is the bones of dead sea creatures and high in Calcium. If it is fed to the chickens they absorb this calcium better.
It also helps keep flies down in the coop. It is not a good idea to breath it when putting in into the coop but is safer to use than poultry dust.
Dusting birds with DE it has to be dangerous to the health of both the human and the chickens. I would counter that its safer than Sevin as its dose is accumulative to the lungs. Once its there its there - like asbestos.
