21 CFR § 507.27 - Holding and distribution.
(a) Animal food held for distribution must be held under conditions that will protect against contamination and minimize deterioration, including the following:
(1) Containers used to hold animal food before distribution must be designed, constructed of appropriate material, cleaned as necessary, and maintained to protect against the contamination of animal food; and
(2) Animal food held for distribution must be held in a way that protects against contamination from sources such as trash.
(c) Shipping containers (e.g., totes, drums, and tubs) and bulk vehicles used to distribute animal food must be examined prior to use to protect against the contamination of animal food from the container or vehicle when the facility is responsible for transporting the animal food itself or arranges with a third party to transport the animal food.
(d) Animal food returned from distribution must be assessed for animal food safety to determine the appropriate disposition. Returned animal food must be identified as such and segregated until assessed.