The Etiology of Mastitis and its Impact on Lipid Peroxidation Product of Dairy Cows

Abstract

Background: On most farms the prevalence of mastitis and the number of infected cows is often unknown. These cases do not show any clinical signs and are identified only by California Mastitis Test (CMT) assessment and Somatic Cell Count (SCC) determination. One of the additional diagnostic methods of mastitis may be involve determination of lipid peroxidation end product in milk. Objective:The aim of the study was to detect the main bacterial pathogens causing mastitis in dairy cows and their impact on lipid peroxidation product, using milk malondialdehyde (MDA) as an indicator of oxidative stress. Methods:During the complex investigation of 123 lactating cows, 612 quarter milk samples were exanimated and classified by clinical examination, abnormal udder secretions, assessment of the CMT, with collecting of milk samples for detection of MDA and bacteriological identification of pathogens causing mastitis.Results: Positive CMT score was recorded of 19.2% (118) exanimated quarters and 12.5% (76) quarters were confirmed bacterial pathogens causing latent (1.3%), subclinical (SM; 8.3%) and clinical (CM; 3.0%) mastitis. The most common bacterial isolates from the mastitis cases were staphylococci (67%) included S. aureus, S. chromogenes, S. haemolyticus and S. warneri. The second most common cause of mastitis were S. uberis and S. faecalis. The concentrations of MDA were significantly higher from SM and CM cases than in milk samples from healthy cows. In addition, we found that quarter milk samples infected with S. uberis were higher MDA levels compared to other pathogens. Conclusion:The higher MDA concentrations in SM and CM milk observed in this study showed that the oxidative stress of infected milk is higher than normal milk. In conclusion, the measurement of milk MDA level could be a potential biomarker for monitoring health status of the mammary gland.