What prevents water loss in animals?

Water loss is a response to several everyday activities. For example, eating salty food will generally lead to more excretion via the kidneys, while physical activity or excess heat will lead through water loss via transpiration. For healthy people the best response is to drink sufficient water so that the normal loss of water from a normal diet and activity level does not lead to dehydration. In some cases there is a pathophysiology and in those cases synthetic hormones of anti-diuretic hormone could be used.