any large blender designed for hard materials would work. You could also just pour the dogfood into a sturdy bin and use a metal rod and pound the dogfood into dust. A garpage pail with a hole cut into the lid (in center) big enough to allow a metal headed stick through (or even a sled hammer would work) this way you can pound the dogfood into powder wihtout worry about pieces flying out.
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PHLdyPayne