I mentioned in another thread that we bought some Iam's canned food from Park n Shop, and our cat wouldn't eat it. She normally eats the Iam's canned food from Red Carrot (the pet store at the top of APM mall)
Curious, I checked out the labels for differences. The stuff from the pet store is labeled as "Premium Cat Food" and from the grocery store it is labeled as "Adult Cat Food". Ironically, the grocery store variety is more expensive (about $5.50 per can instead of $4 per can).
Here are the ingredients:
Grocery Store Version:
Meat Broth, chicken, Poultry Liver, Tuna, Wheat Gluten, Ocean Fish, Dried Beet Pulp, Meat By-Products, Fish Oil, Natural Flavors, Guar Gum, Salt, Titanium Dioxide, Potassium Chloride, Sodium Carbonate, DL-Methionine, Taurine, Vitamins, Minerals
Pet Store Version:
Salmon Broth, Ocean Fish, Beef Liver, Chicken, Corn Oil, Brewers Rice, Dried Egg Product, Fish Meal, Potassium Chloride, Calcium Carbonate, Brewers Yeast, DL-Methionine, Taurine, Vitamins, Minerals, Taurine
As you can see, the grocery store version has a lot of filler (gluten, beet pulp, guar gum) which cats obviously don't need to feed on considering they are a 'pure carnivore'. It also contains meat by-products, "natural flavors," more salts, and even a dye (Titanium dioxide).
Now I'm not an expert so I can't give that kind of advice here.. But as you can see, the Iam's being sold in grocery stores is no different than any other cheap grocery store brand, filled with junk that your cat doesn't need.