N-acetyl-beta-D-glucosaminidase test for screening milk samples for subclinical mastitis

Veterinary Research Laboratories, Stormont, Belfast.

The use of the N-acetyl-beta-D-glucosaminidase (NAGase) test for detecting subclinical mastitis was investigated in surveys of milk samples from 20 farms. A milk sample was considered to be mastitic if it had a milk cell count above 400,000 cells/ml, and the NAGase test results were graded accordingly. The test gave an average of 16.6 per cent false positives and 2.0 per cent false negatives per herd. It was concluded that the NAGase test could be used as a rapid screening method for selecting suspect samples for further analysis by standard methods.