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Effect of paratuberculosis on culling, milk production, and milk quality in dairy herds

Steven H. HendrickDepartment of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada.
Present address is the Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada.

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David F. KeltonDepartment of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada.

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Ken E. LeslieDepartment of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada.

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Kerry D. LissemoreDepartment of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada.

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Marie ArchambaultAnimal Health Laboratory, University of Guelph, Guelph, ON N1H 6R8, Canada.
Present address is the Department of Pathology and Microbiology, Faculty of Veterinary Medicine, University of Montreal, St Hyacinthe, QC J2S 7C6, Canada.

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Todd F. DuffieldDepartment of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada.

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Abstract

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

Design—Cross-sectional study.

Animals—689 lactating dairy cows in 9 herds.

Procedure—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 and Clinical Relevance—Results suggest that for the 9 herds in this study, paratuberculosis significantly decreased milk production and cow longevity. (J Am Vet Med Assoc 2005;227:1302–1308)

Abstract

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

Design—Cross-sectional study.

Animals—689 lactating dairy cows in 9 herds.

Procedure—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 and Clinical Relevance—Results suggest that for the 9 herds in this study, paratuberculosis significantly decreased milk production and cow longevity. (J Am Vet Med Assoc 2005;227:1302–1308)