Dried dung from a herbivore is usually fantastic. there's pretty much no more biological activity once it's dried out, so it's really no worse than burning grass or wood - and it smells a *lot* better than burning grass..

I've done dried cowflop fires and they're actually really good - as long as the cowflops are nice and dry. Seriously.. not gross at all... Think of it like burning particle board that has no carcinogenic glue and crud in it.