Bovine Subclinical Mastitis Diagnosed on the Basis of Amyloid A Protein in Milk

Abstract

Concentrations of serum amyloid A protein (SAA) in serum and milk from healthy cows and cows with subclinical mastitis were measured. In addition, we investigated relations among milk SAA concentration, somatic cell count (SCC), modified California mastitis test (MCMT) scores and bacterial species isolated from milk. There were no differences in serum SAA concentrations between healthy cows and cows with subclinical mastitis. Mean concentrations of milk SAA for each group diagnosed with MCMT were 8.3±13.8μg/ml for negatives, 25.1±26.1μg/ml for repeat examinations, 32.2±65.2μg/ml for suspicious cases and 168±225.2μg/ml for positives. Values for the negative group were significantly lower than those for the other three groups (P<0.01) and the values for the positive group were significantly higher than those for the other three groups (P<0.05). The mean milk-SAA concentration from which Staphylococcus aureus or Streptococcus agalactiae was isolated was significantly higher than those from which Corynecabterium bovis or coagulase-negative staphylococci were isolated. Furthermore there was a significant correlation between the concentration of milk SAA and SCC (r=0.862, P<0.01). These results suggest that concentration of milk SAA rises in subclinical mastitis cases and that the rise may depend on the severity of tissue damage caused by differences in the infecting bacterial species. They also suggest the possibility of SAA production in mammary glands.