in my opinion ,,the above in a nutshell,, some interesting posts here, i think theres a big difference with a prevention, preventative meds,,, and a cure,,,
you cant cure something thats not ill :-/
prevention meds. are sometimes a must [by the rules of some organizations] paramyxo vaccination etc,
but prevention is a great thing, not all can be prevented, but much can,, as owen says about keeping the grit/minerals etc fresh , clean and dry , as damp dirty grits/minerals can be a haven for cocci worms etc, ,, also keeping stress to a minimum,, i,e overcrowding , ventilation, dryness etc , i believe management has much to do with prevention,
so the question "what should i treat my stock birds for?",, in my opinion, spend your money on a swab and droppings test,, its a lot cheaper than treating sometimes, for nothing,