Effect of antibiotic residues from subclinical mastitis on β-lactoglobulin concentration in bovine and goat milk

β-Lactoglobulin (β-LG) is an important milk protein, accounting for approximately 10% of total milk protein and 50–60% of whey proteins. Its concentration can vary depending on the species and several factors, including the use of antibiotics in the treatment of conditions such as subclinical mastitis. If withdrawal periods are not properly observed, antibiotic residues may remain in the milk, compromising its quality and posing risks to consumers. This study evaluated the effect of antibiotic residues from the treatment of subclinical mastitis on the concentration of β-LG in milk from cattle (Bos taurus) and goats (Capra hircus) on farms located in Paipa, Boyacá (Colombia). Twelve milk samples were collected from Simhol and Jerhol cattle and from Saanen and Alpina goats that tested positive for subclinical mastitis using the CMT. Samples were collected before and 24 hours after treatment with beta-lactams and tetracyclines. β-LG concentration was quantified by reverse-phase high-performance liquid chromatography (RP-HPLC), and the data were analyzed using a linear model under a 2×2 factorial design with the following factors: antibiotic residues (present–absent) and species (cow-goat). A significant reduction of 0.43 g L-1 (P<0.05) in β-LG concentration was observed in association with the presence of antibiotic residues, with no interaction with species. These results are exploratory and suggest a possible negative impact of antibiotics on the functional and nutritional quality of milk, potentially related to protein carbonylation processes.