The Halacha is very strict with regard to selling food-products that are forbidden to eat. For example, one is not allowed to do business selling non-Kosher meat. Rav Moshe Feinstein (Russia New York, 1895-1986) was asked whether a pet-shop owner is allowed to sell pet food consisting of non-Kosher meat. He ruled (Iggerot Moshe YD 2:37) that the restriction only applies to foods in which there is a likelihood that someone might eat it. Therefore, it is permitted to sell pet food, since even if edible, it is packaged and clearly designated for animal consumption only.
SUMMARY: It is permitted to sell pet food.
