So I have histomoniasis (blackhead) in my turkeys...

[KhandiKane]

What are you using for roosts? Maybe the width doesn’t agree with their feet? Also, Blackhead occurs when the turkeys eat the worms that have passed through the contaminated soil. I have only ever treated with metronidazole, once a month in a special water mixture that is taken up after 24 hours. I would hesitate to offer any more than that without any kind of symptoms. Since you are somewhat confident this was Blackhead, then you know a preventative measure with the metronidazole would be an option. The only other way to increase your chances of success would be to have the turkeys in cement runs. Hope this helps.

Note: the amount I quoted was for preventative measures, not treatment in the event of an actual case.