Abstract
Subclinical mastitis (SCM) is one of the most economically important diseases affecting dairy animals. The purpose of the present investigation was to evaluate the effects of SCM on the selected hematobiochemical parameters with special emphasis on the biomarkers of inflammatory response and oxidant-antioxidant status. The study was conducted on 50 Holstein Fresian cows classified as 40 SCM and 10 healthy controls based on California Mastitis Test and somatic cell count in milk. Blood and milk samples were collected for the selected hematological and biochemical analyses. The results showed that the SCM cows demonstrated significant decrease in RBC parameters. Total leukocytic and neutrophilic counts showed significant increase, however lymphocyte count was significantly decreased. Biochemical estimation revealed significantly lower serum values of TP, Alb, Glob A/G ratio and prolactin in SCM cows. However, significant elevations were reported in serum glucose, cortisol, and enzymatic activities of ALP and LDH. Serum levels of MDA and NO showed significant increases in SCM cows while, GSH and TAC levels were markedly decreased. The serum levels of inflammatory cytokines implicated significant increases in IL-6 and IL-8 with significant decreases in IL-10 in the affected group compared to controls. The average values of Haptoglobin, Amyloid-A and ceruloplasmin demonstrated significant increases in both milk and serum of SCM cows. All measured acute phase proteins yielded the same sensitivity and specificity. Ceruloplasmin had the highest percentage of increase in milk while amyloid-A had the highest percentage of increase in serum. The present study can conclude that APPs, pro-inflammatory cytokines, and oxidative stress indices may serve as valuable biomarkers for diagnosis of SCM in cows. Among APPS, milk ceruloplasmin can be considered the most reliable for detection of SCM, while in serum, amyloid A appeared to be the protein that can relied upon in the diagnosis of the disease in cows.

Key words: Acute phase proteins, inflammatory cytokines, subclinical mastitis, California Mastitis Test, oxidative stress