Limited ingredient and grain free are 2 different things, but there are dogs foods out there that are both. Acana has lines of limited ingredient and single ingredient foods that are grain free. PetSmart doesn't sell Acana, but if you buy things on Amazon, it can be bought on Amazon. Also, if you have a Pet Supplies Plus close to where you live they carry Acana. It's an excellent brand I would feel comfortable feeding my dog if I fed kibble. I would not feed a dog food that the first ingredient is sweet potato though. I'm not opposed to sweet potato -- I bake a sweet potato in the microwave for Lulu these days about every other day as a snack (takes her 2 days to eat it with me giving it out as a treat), and she practically does back flips for it--loves it, but I wouldn't like it as the main ingredient in the food I feed her.
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