DISCUSSION: FCMF makes delivering a predictable, accurate, and intended dose difficult.
Feeds containing medically active ingredients, such as antibiocic and antiparasitic drugs or insecticides, that are fed on a "free-choice" basis, are designated free-choice medicated feeds (FCMF) by the U.S.
The use of FCMF in food animals has been associated with imprecise drug intake, leading to under- or overadministration of drugs (Figure 1) (Bogan and Marriner 1983; Hall 2000; Toutain et al.
The purpose of this commentary is to discuss the history of medicated feed, the nature of FCMF use, and its role in the development of antimicrobial-resistant microorganisms.
A fraction of livestock herds refuse FCMF; these animals were shown to have low serum and plasma concentrations of drugs (Bogan and Marriner 1983).
When FCMF are freely available to livestock, they may be available to wildlife living on or near animal production operations.
Taken in sum, numerous factors influence the ability to deliver predictable or intended doses of drugs to animals via FCMF. Given the limited oversight, the availability of FCMF without a veterinary prescription, the potential for undeclared drugs, and variability in drug concentrations within and between feeds, unintended (and therefore inappropriate) drug delivery is likely.