honestly, i'd suggest getting the known culprit tested for a UTI ... or possibly diabetes/hyperglycemia =/ the carb content is the main difference from purina to TOW, so increased pee -could- be linked to insulin levels changing. i don't see anything in the TOW ingredient list that screams diuretic, and it doesn't have extra salt either so i see no reason why they'd drink more on it. unless the fish they use is naturally salty? you should try a piece lol.

course, i'm not a vet, i just worked in the pet food industry for a while. i just personally like to rule health problems out first instead of last.
if you feel up to experimenting, you could try separating the two cats to see if they're both doing it or just one. is it the male or female that you know for sure?
farmerchick - your barn cats probably supplement their diets with things that are better for them than any kibble could be.

i truly believe in good nutrition, for people and animals both, it just makes sense. and some store brands are better/worse than others. just because some people can eat mcdonald's every day and not show health problems, doesn't make it a good diet. just because a cat can eat Brand X and "be fine" doesn't make it a good diet. cats are obligate carnivores, they are designed to eat meat; a cat food high in carbs is simply not what they're meant to have. that doesn't mean every single cat on a high-carb diet will have problems, but it does increase the chances. i'm totally not lecturing you or anything btw, just discussing. all cats are individuals, some are more sensitive than others, and you know best what's working for your individual cats.
