Milk antitrypsin as a marker of bovine mastitis--correlation with bacteriology

Milk antitrypsin reflects leakage of protein of blood plasma into milk. Mastitis detection can be based on measurement of the trypsin-inhibitor capacity in milk; the "Eflab Mastitis Test" procedure is based on this principle. The procedure was developed to screen for subclinical mastitis; high capacity and sensitivity permits whole herds to be analyzed on a quarter basis to identify inflamed quarters during a single sampling. Milk antitrypsin was measured on 2174 quarter milk samples by a colorimetric procedure. The Multiskan MC reader was hooked to desk computer to interpolate antitrypsin from the standard curve and to analyze results. The analysis of inflammation was based on antitrypsin as well as computerized interquarter evaluation. These measures were compared with bacteriologic study of milk to set criteria for automatic identification of mastitis in individual quarters. The comparison against the lowest teat antitrypsin gave better indication of infection than antitrypsin as such. By strict criteria that identified inflammations caused by major pathogens, 18.8% of uninfected quarters were identified as false positive. The explanation is that a single bacteriological culture is not reliable for detecting mastitis, because there are temporary causes of tissue irritation other than bacteria that may be identified during standard bacteriologic examination.