Characterization of Antimicrobial Use and Detection of Antimicrobial Residues in Bulk Tank Milk From Specialized Dairy Herds in Antioquia, Colombia.

Antimicrobial residues in bulk tank milk (BTM) are often linked to the treatment of bovine mastitis, the main disease in specialized dairy herds. These residues cause economic losses, especially in fermented dairy production and may pose health risks to consumers. Limited data exist on antimicrobial residues in raw milk in Colombia; thus, this study aimed to characterize antimicrobial use and detect residues in BTM from specialized dairy herds. A probabilistic selection of 150 herds from three municipalities in Antioquia, Colombia, was carried out for an epidemiological survey in which each herd was visited once to determine the use of antimicrobials on the farm and for bovine mastitis. One BTM sample per herd (n = 150) was evaluated with the Brilliant Black Reduction Test (BRT), Milksafe™ 2BC, and Milksafe™ 3BTS, for the selective detection of beta-lactam, sulfonamide, and tetracycline residues. Survey results showed that bovine mastitis is the main reason for the use of antibiotics in the dairy herds in the study region. In 47% of herds, antimicrobials were recommended by nonveterinarians, and 78% lacked written treatment records. Cloxacillin-ampicillin was the most used for dry cow therapy, while benzylpenicillin was preferred for mastitis. Antimicrobial residues were found in 13% (19/150) of bulk tank milk samples. Of these 19 positive samples, four samples contained beta-lactams and one sample contained sulfonamides. According to survey data, bovine mastitis is the primary disease in herds for which antibiotics are used and antimicrobial residues in raw milk are present imposing a significant risk for consumers in the region. Therefore, it is a priority to reduce bovine mastitis incidence as well as the application of a program for on-farm antimicrobial administration, oriented to the reduction of the economic impact of inadequate treatments that lead to therapeutic failure and penalties in the price of milk.