Norman, my cat can only eat 1 type of cat food: Purina Pro Plan Chicken and Rice in the 3 oz can. All other vendors and flavors cause stomach upset. Purina Pro Plan Chicken and Rice in the 6 oz gives him stomach upset. Getting either the 6 oz or 3 oz cans from Chewy (a pet products online retailer) also results in stomach upset. If the 3 oz cans are purchased from a brick-and-mortar retailer (actual store) Norman has no stomach upset. We are mystified about the differences in the product. 

Does the supply chain have any technology to help us understand the differences in Norman's cat food which should be the same? or track product quality? What other production and supply chain issues could account for what appears to be the same product, but is obviously not the same product?