Efficacy of Copper Ion Treatment on Bacteria and Antibiotic Residues Contained in Bovine Waste Milk.

Background/Objectives : Waste milk harbors many bacteria and antibiotic residues. Calves fed with untreated waste milk have a higher incidence of scours and an increased risk of developing antimicrobial-resistant bacteria. This study aimed to evaluate the efficacy of treatment with copper ions on bacteria and antibiotics contained in bovine waste milk. Methods : Waste milk samples were collected from a dairy farm for seven weeks and were subjected to treatment with copper ions. Total bacterial counts, coliforms, Streptococcus , and Staphylococcus were assessed before and after treatment. Additionally, metagenomic analysis was performed to determine microbial diversity. Results : Before treatment, the total bacterial count average was 4.0 × 10 ⁶ CFU/mL, 1.7 × 10 ⁴ CFU/mL for coliforms, 2.6 × 10 ⁶ CFU/mL for Streptococcus , and 5.4 × 10 ² CFU/mL for Staphylococcus Copper treatment significantly reduced bacterial counts within 15 min. Total bacteria decreased from 4.0 × 10 ⁶ CFU/mL to 1.1 × 10 ² CFU/mL after 30 min; meanwhile, other groups were not detected. The most abundant groups were Lactococcus (29.94%), Pseudomonas (28.89%), and Enterobacteriaceae (21.19%). Beta-lactams were detected in five-sevenths samples, and in one sample they were detected before and at 15 min of treatment but not after 30 min. Conclusions : The effect of treatment with copper ions on the different bacterial groups was significantly effective but showed limited effect on the detection of antibiotics.