Ceftiofur is a broad-spectrum cephalosporin approved primarily for the parenteral injection treatment of gram neg. bacterial infections in cattle, swine, sheep, day-old poultry, horses, and dogs.- Ceftiofur is minimally bioavailable after oral administration.- Ceftiofur undergoes rapid and extensive metabolism to desfuroylceftiofur (DFC) and conjugation after administration (half-life of less than 5 min).- Many of these conjugates are microbiol. active. -Tolerances for ceftiofur are based on an assay that measures all DFC-related residues. Ceftiofur hydrochloride administered IM or SC has a 2-day tissue withdrawal time, whereas ceftiofur sodium administered IM has a zero-day tissue withdrawal time.- Ceftiofur has no milk discard when administered parenterally to lactating dairy cattle, due to the limited absorption/distribution of drug into the milk from the systemic circulation.- This presentation will describe the overall metabolism, residue decline, residue anal., and the ultimate degradation of ceftiofur in various species.