From the Ithaka journal, "Biochar in poultry farming "
http://www.ithaka-journal.net/pflanzenkohle-in-der-geflugelhaltung?lang=en

This is a practical article that provides simple advice for using biochar to help manage disease in commercial poultry operations. The authors point out that many birds end up spending time in direct contact with their manure and suggest blending 5-10% by volume biochar into the bedding or silage used to in the coops and poultry houses can help the birds resist diseases in addition to helping filter the ammonia and reducing the impacts of the bird wastes.

The primary article also gives specific recommendations for using biochar in feed to help prevent intestinal diseases, and they recommend the following studies: