Hi

Would totally agree with Spid, its probably to do with the food. Hate to say it, but Go Cat has the nickname 'Gone Cat' among most cat experts. It is totally bulked out with grains and cats dont have a digestive system that can cope with grains as they are obligate carnivores (means they need to eat meat).

Have a look at this link, its by vet Lisa A. Pierson, DVM and it may explain things a bit better. http://www.catinfo.org/