Assessment of the visually read N-acetylglucosaminidase test to detect mastitis in herd surveys
Ball, H.J.; Davidson, B.; Greer, D.
Veterinary Record 124(6): 145-146
1989
ISSN/ISBN: 0042-4900 PMID: 2929088 Document Number: 333523
The N-acetylglucosaminidase (NAGase) activity of 1020 bovine quarter milk samples from 7 farms was estimated using duplicate 10 micro /litre aliquots of milk, which were mixed with 4-methyl umbellyferyl-N-acetyl- beta -D-glucosamide and a fluorescent standard, 4 methyl-umbelliferone. Emitted fluorescence was viewed under a UV lamp and estimated independently by 3 people. Milk cell counts (MCC) and bacterial culture of the samples were also carried out. High MCC totals were detected in 260 samples. NAGase activity was detected in 252 samples by all 3 readers and in 544 samples by 1, 2 or 3 readers. Of the 260 samples with high MCC, 185 (71%) had NAGase activity which was detected by all 3 readers and 237(91%) had NAGase activity detected by 1, 2 or 3 readers. Streptococcus species were isolated from 76 of 132 samples; of these 76 samples, 60(79%) had high MCC totals and 66-85.5% had detectable NAGase activity. Staphylococcus aureus was isolated from 80 of 1020 samples; of these 80 samples, 59 (67%) had high MCC totals and 59-86% had detectable NAGase activity. The NAGase test was rapid and easy to perform. Fluorometric measurement should enable the NAGase border line to be better defined and the test better evaluated.