Effect of paratuberculosis on culling, milk production, and milk quality in dairy herds.
OBJECTIVE
To determine the effect of paratuberculosis on culling, milk production, and milk quality in infected dairy herds.


METHODS
Cross-sectional study.


METHODS
689 lactating dairy cows in 9 herds.


METHODS
Milk, blood, and fecal samples were obtained from all cows. Fecal samples were evaluated via mycobacterial culture. Serum samples were tested with a commercially available ELISA for antibodies against Mycobacterium avium subsp paratuberculosis, and preserved milk samples were tested with an ELISA for antibodies against M paratuberculosis. Mixed effect and proportional hazards models were used to determine the effect of paratuberculosis on 305-day milk, fat, and protein production; somatic cell count linear score; and the risk of culling.


RESULTS
Cows with positive results of bacteriologic culture of feces and milk ELISA produced less milk, fat, and protein, compared with herdmates with negative results. No difference in 305-day milk or fat production was detected in cows with positive results of serum ELISA, compared with seronegative cows. The 3 survival analyses revealed that cows with positive results of each test were at higher risk of being culled than cows with negative results. Paratuberculosis status, as determined by use of all 3 diagnostic tests, was not associated with milk somatic cell count linear score.


CONCLUSIONS
Results suggest that for the 9 herds in this study, paratuberculosis significantly decreased milk production and cow longevity.
Hendrick
Steven H
SH
Department of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada.
Kelton
David F
DF
Leslie
Ken E
KE
Lissemore
Kerry D
KD
Archambault
Marie
M
Duffield
Todd F
TF
D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D002417:Cattle; D002418:Cattle Diseases / Q000401:mortality / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005243:Feces / Q000382:microbiology; D005260:Female; D007774:Lactation; D008892:Milk / Q000737:chemistry / Q000378:metabolism* / Q000382:microbiology / Q000592:standards*; D016927:Mycobacterium avium subsp. paratuberculosis / Q000276:immunology / Q000302:isolation & purification; D010283:Paratuberculosis / Q000401:mortality / Q000503:physiopathology*
D000907:Antibodies, Bacterial