The present study was conducted to evaluate the concentrations of sialic acids (total, lipid bound and protein bound) and their correlation with acute phase proteins (haptoglobin and serum amyloid A) in clinical and subclinical mastitis of cattle. Thirty subclinical mastitic cows with positive California mastitis test (CMT) test and no clinical signs of mastitis, 10 clinical mastitic cows and 10 healthy cows with negative CMT test and normal somatic cell count were selected. Milk and blood samples were collected after confirmation of clinical and subclinical mastitis by somatic cell count and bacterial identification. Serum haptoglobin (Hp), serum amyloid A (SAA), total sialic acid (TSA), lipid bound sialic acid (LBSA) and protein bound sialic acid (PBSA) were measured by validated standard methods. Haptoglobin and SAA increased significantly in both types of mastitis compared with control group (P<0.001). However, the ratio of HP/SAA was significantly different from the control group only in clinical mastitis. The results showed that TSA and LBSA were significantly different in control group compared with clinical and subclinical mastitis (P<0.001). Protein bound sialic acid did not change in subclinical mastitis in comparison with control group (P=0.86). There was positive correlation between LBSA and PBSA in clinical mastitis (r=0.72, P=0.02) whereas significant negative correlation was observed between LBSA and PBSA in subclinical mastitis (r=-0.62, P<0.001). Results also showed no correlation between Hp and SAA with each other or with any other parameters in study groups.

Key words: Cattle, Clinical and subclinical Mastitis, Haptoglobin, Serum amyloid A, Sialic acid