Association of Mastitis and Farm Management with Contamination of Antibiotics in Bulk Tank Milk in Southwest, China

SIMPLE SUMMARY: Antibiotic contamination of animal food sources is an important public health problem between animals and humans; milk is an important source of protein for people and one of the foods with antibiotic residues. Antibiotics residues in milk often come from antibiotic treatment of cow mastitis. Through a questionnaire survey study, we found that farmers on most smallholder farms have poor awareness of stewardship and disease management. Some farmers cannot accurately answer the types and usage of antibiotics. Our study also showed that there was a big gap in management between large and smallholder farms in Southwest China, which is the main reason for the prevalence of mastitis in dairy cows and the antibiotic residue rate in bulk tank milk. Our results suggest that dairy farmers need to improve their knowledge of dairy cow diseases and antibiotic use; for non-professional farmers, we recommend listening to the treatment options provided by a professional veterinarian. ABSTRACT: Bovine mastitis could reduce the milk production and the quality of the bulk tank milk (BTM). Antibiotic treatments through intramammary or parenteral methods are being widely used in dairy farms. A cross-sectional study to investigate for general farm management and pre-test the questionnaire was performed in Southwestern Yunnan province, China. A total of 134 dairy farms were included. Milking cows of each farm were determined for the presence of clinical (CM) and sub-clinical (SCM) mastitis using the California Mastitis Test (CMT). Rates of CM and SCM in studied farms ranged from 2–11%, and 24–69%, respectively. The incidence of antibiotic residues in BTM of all farms was very high (32%, 44/134). All antibiotic contaminated samples were from smallholder dairy farms. Factors significantly associated with the presence of antibiotic contamination included farm region, antibiotics usage, persons performing mastitis treatment, and rates of CM. Rates of CM were significantly associated with the farm region, cleanliness of udders before milking, and the number of milking cows. Our results emphasize that the risk factors of dairy farm management should be paid attention, which can reduce mastitis prevalence and antibiotic contamination in BTM in Southwestern China.