Abstract
The beginning of lactation in dairy cows is a challenging period when cows experience oxidative stress followed by an increased risk of mastitis. This study aimed to establish a correlation between mastitis pathogens and the activity of antioxidant enzymes – superoxide dismutase (SOD) and glutathione peroxidase (GPX) – in milk collected from cows with mastitis compared with their healthy counterparts. During the two-year survey, the udder health status was followed and the changes in SOD and GPX activity in milk were assessed in the period to 42nd day of lactation. The quarter milk samples were screened for detection of abnormal milk secretion (AMS) and intramammary infections (IMI). The spectrophotometric methods were used for detection of antioxidant enzyme activity in milk serum. The prevalence of IMIs from AMS was 43.83% while the isolated mastitis pathogens were grouped as contagious: Streptococcus agalactiae (19.14%) and Staphylococcus aureus (6.17%); or environmental: Enterococcus spp. (8.02%), Pseudomonas aeruginosa (7.41%), Escherichia coli (1.85%), and Aspergillus niger (1.23%). IMI showed statistically significant influence on SOD and GPX activity in milk serum (p<0.05). Contagious bacteria lead to increased activity of GPX, while environmental pathogens more drastically increase SOD activity. Providing a balanced diet with adequate antioxidants and managing environmental stressors can help reduce oxidative stress during the transition period and decrease the risk of mastitis in early lactation.