Classification of bovine milk samples by using a new N-acetyl-beta-D-glucosaminidase activity measurement

A new, simple and rapid spectrophotometric method for N-acetyl-beta-D-glucosaminidase (NAGase) activity measurement using Clarifying Reagent(R) has been applied to the differentiation of some individual milks towards a possible mastitis. Enzymatic activity measured by this method on 52 individual raw milk samples was well correlated (r=0,80) to the somatic cell count (SCC). The NAGase activity measured by the usually spectrofluorometric method was also well correlated to the SCC (r=0,76). The 52 individual raw milk samples have been distributed among 3 classes according to their SCC. Class I with SCC<200,000 collected samples of good hygienic quality. Class II with SCC ranged from 200,000 to 400,000 identified doubtful samples and class III with SCC>400,000 contained suspicious mastitic or submastitic milk samples. The 2 used enzymatic methods permit the same classification of these milk samples with the 3 significantly different classes. NAGase activities of classes I and II partially overlay, but their mean values were significantly different. Experiments on 5 samples have demonstrated that the spectrophotometric method is also suitable for differentiation of bulk milk. This study shows, that it is possible to classify milk samples according to their degree of infection by using only NAGase activity.