Reply #19: This article about UTD and cat food is interesting

[marzipanni]

Years ago I had a neutered male cat who pee'd in the bathtub, and I thought he was smart to show me that something was wrong- his urine was pink. In those days we were told that male cats are susceptible to getting urinary tract problems due to high ash in their food. This article says it's the pH of the cats urine, which the food affects, and you can find out the target range for various foods.

http://cats.about.com/od/lowerurinarytractdisease/qt/catsurinpH.htm