Some archived postings about Diatomaceous Earth for your horse:

https://askdrdan.com/HOME/2009/03/29/a-question-about-diatomaceous-earth/ https://askdrdan.com/HOME/2008/08/27/fly-predators-and-diatomaceous-earth/ https://askdrdan.com/HOME/2008/08/12/diatomaceous-earth-as-a-dewormer/   Also Every "Mention" (via search): https://askdrdan.com/HOME/?s=%22Diatomaceous+Earth%22&submit=Search