The effect of sub-clinical infection with Mycobacterium avium subsp. paratuberculosis on milk production in a New Zealand dairy herd
- PMID: 29540214
- PMCID: PMC5853068
- DOI: 10.1186/s12917-018-1421-4
The effect of sub-clinical infection with Mycobacterium avium subsp. paratuberculosis on milk production in a New Zealand dairy herd
Abstract
Background: Johne's disease is a major production limiting disease of dairy cows. The disease is chronic, progressive, contagious and widespread; there is no treatment and there is no cure. Economic losses arise from decreased productivity through reduced growth, milk yield and fertility and capital losses due to premature culling or death. This study attempts to address the effect of subclinical JD on milk production under New Zealand pastoral dairy farming conditions using a new testing approach. Blood samples were taken from all lactating animals from a single seasonally calving New Zealand dairy herd in the autumn of 2013 and 2014. Samples were subject to serological assay for antibodies to Mycobacterium avium subsp. paratuberculosis using a combination of four ELISA tests in parallel followed by selective quantitative fecal PCR to confirm the fecal shedding characteristics of ELISA positive cows. ELISA status was classified as Not-Detected, Low, Moderate or High and fecal PCR status as Not-Detected, Moderate or High.
Results: A mixed generalized regression model indicated that, compared to cows where MAP was not detected, daily milk solids production was 4% less for high ELISA positive cows (p = 0.004), 6% less for moderate fPCR cows (p = 0.036) and 12% less for high fPCR cows (p < 0.001).
Conclusions: This study confirms that sub-clinical JD can have a significant impact on milk production and that the testing methodology used stratified the animals in this herd on their likely impact on production and disease spread. This allowed the farmer to prioritize removal of heavily shedding, less-productive animals and so reduce the risk of infection of young stock. This is the first longitudinal study based in New Zealand looking at the effect of Johne's infection status on daily milk production allowing for intermediary and confounding factors.
Keywords: ELISA; Johne’s disease; Milk production; Quantitative PCR.
Conflict of interest statement
Ethics approval and consent to participate
Ethics approval is not applicable. Animal handling and sample collection was performed or supervised by approved veterinarians. Consent was obtained from the farmer for the samples collected at their farm.
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
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References
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- Hunnam J. Johne’s control is possible: does anyone have a MAP? In: Proceedings of The Society of Dairy Cattle Veterinarians of the NZVA Annual Conference. NZVA; 2014. pp. 133–150.
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- Smith RL, Grohn YT, Pradhan AK, Whitlock RH, Van Kessel JS, Smith JM, Wolfgang DR, Schukken YH. The effects of progressing and nonprogressing Mycobacterium avium ssp. paratuberculosis infection on milk production in dairy cows. J Dairy Sci. 2016;99(2):1383–1390. doi: 10.3168/jds.2015-9822. - DOI - PMC - PubMed
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