Recent walk through the cranberry bogs in Pine Barrens, NJ and it seemed the dog was dehydrated ... lethargic, not marking territory, dark yellow pee. The water is heavy in iron and bacteria attach to the iron making it taste disgusting (rotten eggs).
I need to stop every so often and give the dog a bowl of filtered water, and to make sure he drinks it all. Internet search say add beef or chicken consume to the water to make it more attractive. Unfortunately I have not found a product that has no onions (deadly to dogs) and is low in salt. Lipton chicken noodle packets have no onions, but plenty of salt.
The vet was no help. Anyone out there deal with this ... you desert hikers?