Milk quality parameters associated with the occurrence of veterinary drug residues in bulk tank milk

Veterinary drug residues in bulk tank milk are important to all sectors of the dairy chain because they are one of the major factors which determine the safety of the final product. This study attempted to identify milk quality parameters that are associated with the occurrence of veterinary drug residues using multivariate principal component analysis (PCA). A total of 132 raw milk samples were collected from 45 dairy farms in the state of Minas Gerais-Brazil and analyzed for 42 analytes, including pyrethroids, macrocyclic lactones and antibacterials, using liquid chromatography coupled with mass spectrometry in tandem mode and gas chromatography with electron capture detection. Out of the 132 milk samples, 40 samples tested positive for at least one analyte (above the detection limit). The milk parameters associated with the antimicrobial residues by confirmatory tests were lactose and nonfat concentrations, as revealed by PCA. This analysis showed that fat and total solid concentrations, as well as the somatic cell and total bacteria counts were associated with macrocyclic lactone residues in bulk tank milk. A PCA assessing pyrethroid residues in bulk tank milk revealed that the lactose and nonfat solid concentrations and titratable acidity were inversely associated with these residues. Thus, the data analysis indicated that the veterinary drug residues were associated with certain milk quality parameters that can be used to target farms at higher risk of veterinary drug residue contamination for testing programs in combination with incentives, education and training programs to improve mammary health, milk hygiene and safety.