Do an internet search on food grade Diatomaceous Earth. It is for animal and HUMAN consumption. You can buy it at the Tractor Supply in the Livestock supply area. Make sure it is food grade and NOT the type you use in swimming pools. It will work to deworm animals of all types and even humans. It is perfectly safe and will get rid of weevils in feed but won't hurt your horses or livestock. It will kill fleas...it works for a number of issues regarding pests but will not hurt people or animals. Check it out so you know how much to use.