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N-acetyl-β-D-glucosaminidase (NAGase) levels in bulk herd milk

Published online by Cambridge University Press:  01 June 2009

Barry J. Kitchen ,
Gordon Middleton ,
W. Seng Kwee  and
R. Jeffrey Andrews
Barry J. Kitchen
Affiliation:
Otto Madsen Dairy Research Laboratory, Department of Primary Industries, Hamilton, Brisbane 4007, Australia
Gordon Middleton
Affiliation:
Otto Madsen Dairy Research Laboratory, Department of Primary Industries, Hamilton, Brisbane 4007, Australia
W. Seng Kwee
Affiliation:
Otto Madsen Dairy Research Laboratory, Department of Primary Industries, Hamilton, Brisbane 4007, Australia
R. Jeffrey Andrews
Affiliation:
Dairy Field Services Branch, Department of Primary Industries, Wacol, Brisbane 4076, Australia
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Summary

N-acetyl-β-D-glucosaminidase (NAGase) levels and somatic cell counts (SCC) were determined monthly for 6 months in the bulk milk of 181 suppliers (1063 samples). A highly significant correlation (r = 0·74; P < 0·001) was found between supplier's bulk herd milk geometric mean NAGase activity and SCC. Monthly trends which grouped suppliers into various categories defined by different NAGase and SCC thresholds showed that a similar overall pattern was obtained with both SCC and NAGase. However, further analysis indicated that 18% of the bulk milk which had SCC < 500 × 103/ml had NAGase levels > 25 units. Also, 34% of samples with SCC > 500 × 103/ml had NAGase levels < 25 units. Overall, 24% of all samples did not have corresponding NAGase and SCC results. When the bulk milk of 2 commercial dairy herds was tested monthly over 12–18 months whilst the infection status of all quarters in the herds was regularly monitored, those herds with low incidence of mastitis (5% quarters infected) had significantly lower bulk milk SCC and NAGase levels than those with a high incidence of mastitis (22% of quarters infected). This suggests that NAGase measurement on bulk herd milk would be a simple means of monitoring infection status of dairy herds and of rapidly classifying a supplier's milk as being of low, medium or high SCC status. The possible combined use of SCC and NAGase levels in bulk milk monitoring schemes is discussed.

Type
Original Articles
Information
Journal of Dairy Research , Volume 51 , Issue 2 , May 1984 , pp. 227 - 232
Copyright
Copyright © Proprietors of Journal of Dairy Research 1984

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References

REFERENCES

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