The FDA issued new guidance (GFI #273) in February 2026 to define the duration of use of antibiotics in livestock feed[1][2]. The guideline deals with more than 100 substances that are important for human medicine and have at least one indication without a fixed duration[2]. Approximately 30% of all medically important antibiotics used in the US in cows, pigs, and poultry do not have a defined use time, allowing farmers to use these antibiotics in feed indefinitely[1]. The new guidance recommends that drug manufacturers indicate on product labels an approximate duration and a maximum time that should not be exceeded[1]. FDA expects that manufacturers should have approved revised product labeling within approximately three years of publication of this guidance[2]. The aim of this change is to reduce the development of resistance of microorganisms to antibiotics and to support their reasonable use in animal husbandry[1][2].