Frequency of Antibiotic Residues in a Central Wisconsin Dairy

Abstract

Antibiotics, used to maintain healthy dairy animals, persist in milk produced by treated animals for several days after therapy. Antibiotic residues, if present in the milk supply, negatively impact suitability for processing and consumption. This is an area of concern in the dairy industry and for the general public. This study explores the incidence of antibiotic residues in milk provided to a Central Wisconsin dairy. Random, unidentified samples were obtained over a four month period from producers located within a 100-mile radius of a dairy located in Granton, Wisconsin. All samples were tested within one week of their receipt, and maintained at refrigerated temperatures at all times prior to testing. Following testing, the origin of the samples was revealed. Samples were derived from two milk populations: those intended for human consumption (bulk milk), and those from cows under surveillance following antibiotic treatment (milk removed from the commercial supply). All bulk milk samples tested negative for over 55 different antibiotic residues, while all samples from the surveillance population tested positive for antibiotic residues. Our results are consistent with those observed nationally, and suggest that dairy producers recognize the ongoing concern of antibiotic contamination in the milk supply and are taking steps to prevent antibiotic contamination in milk. Our findings also suggest the public should have minimal concern with respect to antibiotic residues in the commercial milk supply.