Interrelationship between somatic cell count and acute phase proteins in serum and milk of dairy cows

The aim of the present study was to compare the concentrations of two acute phase proteins, haptoglobin (Hp) and serum amyloid A (SAA), in serum and milk of Holstein-Friesian dairy cows grouped according to somatic cell count thresholds (< 100,000 < 400,000 > 400,000 cells/ml) in composite milk samples. The SCC was assessed quantitatively by FOSSOMATIC 90 analyser; serum and milk Hp and SAA concentrations were determined using commercial ELISA kits (Tridelta Development, Ltd., Wicklow, Ireland). We have found a significantly higher Hp and SAA concentrations in the group with SCC > 400,000 cells/ml compared to groups with lower SCC thresholds in composite milk samples. In contrast, significant differences were not demonstrated between the groups in Hp and SAA concentrations determined in serum. The concentrations of Hp in serum and milk were found to be correlated (r = 0.69, P = 0.0003), whereas there was a lower correlation trend in the case of serum versus milk concentrations of SAA (r = 0.43, P = 0.0478). High significant correlations were observed either between milk haptoglobin values and SCC or milk serum amyloid A concentrations and SCC (r = 0.83, r = 0.81, P < 0.0001; respectively). An increase in SCC in cows suffering from mastitis has been accompanied by strong elevation of the milk Hp and SAA, significantly correlated with serum Hp (r = 0.64, P = 0.0014) and poorly correlated with SAA values determined in serum (r = 0.43, P = 0.0478). According to the results obtained in this study we can conclude that measurements of the acute phase proteins, haptoglobin and serum amyloid A predominantly in milk, may be a useful tool in diagnosing mastitis and may be a useful marker of milk quality.