Purina products do not have a fixed formula. They use whatever ingrediants are cheapest at each individual mill. They have multiple feed mills all over the country. If you have someone pull a feed tag for a bag of feed in California and someone pull a tag for same feed in Florida, you'll get different ingrediants.
The number of feed recalls over the years makes me VERY hesitant to use any of their prodcts, that along with their non-fixed formula.