Feedlots and other growers of food-producing animals sometimes adopt the practice of separately feeding different medicated feeds, perhaps one in the morning and a second in the afternoon, both containing drugs which, if in a single feed, would require an approved medicated feed application. This brings into question drug safety and effectiveness, including the potential for illegal residues, resulting from drug interference, potentiation, or other factors.
In some instances, medicated feed label directions for use are required to specify that the medicated feed is to be fed as the sole ration. In most instances, however, medicated feed labels are silent on the issue.
The FDA does not approve of the practice of alternate feeding of different medicated feeds, even when not specifically prohibited by the labeling of the medicated feeds. If this practice results in above tolerance tissue residues, a violation of Section 402(a)(2)(D) occurs. If a producer holding an approved medicated feed application practices alternate feeding in opposition to labeling approved for feeding as the sole ration, a violation of Section 512(m)(4) occurs and subjects the approved medicated feed application to consideration of withdrawal proceedings if voluntary correction cannot be obtained.