Our boy is strictly on urinary food, and soon after my girls started throwing up constantly, we originally were put onto Z/D but found it was far too expensive, we swapped them over to this and they LOVE it. My one gained a whole pound on this food, she is usually very hard to feed. Now shes a little piggy! the packaging before stated it was ST/OX compatible which was peace at mind for if our boy got into their food(He has crystals) however the most recent bag did not state this and had a different design....change in formula again?