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Associations between paratuberculosis ELISA results and test-day records of cows enrolled in the Irish Johne's Disease Control Program
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2017-07-12
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Botaro, B., Ruelle, E., More, S., Strain, S., Graham, D., O'Flaherty, J., Shalloo, L. Associations between paratuberculosis ELISA results and test-day records of cows enrolled in the Irish Johne's Disease Control Program. Journal of Dairy Science, 2017, 100(9), 7468 - 7477. doi: https://doi.org/10.3168/jds.2017-12749
Abstract
The effect of the Mycobacterium avium ssp. paratuberculosis (MAP) ELISA status on test-day milk performance of cows from Irish herds enrolled in the pilot
national voluntary Johne’s disease control program
during 2013 to 2015 was estimated. A data set comprising 92,854 cows and 592,623 complete test-day records
distributed across 1,700 herds was used in this study.
The resulting ELISA outcome (negative, inconclusive,
and positive) of each cow within each year of the program was used to allocate the cow into different scenarios representing the MAP status. At MAPscenario1,
all cows testing ELISA nonnegative (i.e., inconclusive
and positive) were assigned a MAP-positive status; at
MAPscenario2 only cows testing ELISA-positive were
assigned a MAP-positive status; at MAPscenario3 only
cows testing ELISA nonnegative (inconclusive or positive) and gathered exclusively from herds where at least
2 further ELISA nonnegative (inconclusive or positive)
cows were found were assigned a MAP-positive status;
at MAPscenario4 only cows testing ELISA-positive that
were gathered exclusively from herds where at least 2
further ELISA-positive cows were found were assigned
a MAP-positive status. Milk outputs based on test-day
records were standardized for fat and protein contents
(SMY) and the effect of MAP ELISA status on the
SMY was estimated by a linear mixed effects model
structure. The SMY mean difference recorded at test
day between cows with a MAP-positive status and those
with a MAP-negative status within MAPscenario1 was
estimated at −0.182 kg/test day; the mean difference
was −0.297 kg/test day for MAPscenario2; for MAPscenario3 mean difference between MAP-positive status
and MAP test-negative cows was −0.209 kg/test day,
and for MAPscenario4, the difference was −0.326 kg/
test day