title: The effects of progressing and nonprogressing Mycobacterium avium ssp. paratuberculosis infection on milk production in dairy cows.
abstract: Longitudinal data from 3 commercial dairy herds in the northeast United States, collected from 2004 to 2011, were analyzed to determine the effect of Mycobacterium avium ssp. paratuberculosis (MAP) infection status and progression path on milk production. Disease status, as indicated by MAP test results, was determined through quarterly ELISA serum testing, biannual fecal culture, and culture of tissues and feces at slaughter. Milk production data were collected from the Dairy Herd Information Association. Animals with positive MAP test results were categorized, based on test results over the full course of the study, as high path (at least one high-positive culture) or low path (at least one positive culture or ELISA). The cumulative numbers of positive ELISA and culture results were recorded. The effects of both MAP infection path, status, and number of positive tests on milk production were analyzed using a mixed linear model with an autocorrelation random effect structure. Low- and high-path animals produced more milk before their first positive test than always-negative animals, especially high-path animals. Although mean production decreased after a first positive test, low-path animals were shown to recover some productivity. High-path animals continued to exhibit a decrease in milk production, especially after their first high-positive fecal culture. These results show that not all animals that test positive for MAP will have long-term production losses. Milk production decreased significantly with each additional positive test. Ultimately, production loss appeared to be a function of MAP infection progression.
authors.affiliation: Department of Pathobiology, University of Illinois College of Veterinary Medicine, Urbana 61802. Electronic address: rlsdvm@illinois.edu.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Smith
authors.affiliation: Department of Population Medicine and Diagnostic Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY 14850.
authors.forename: Y T
authors.initials: YT
authors.lastname: Gröhn
authors.affiliation: Department of Nutrition and Food Science and Center for Food Safety and Security Systems, College of Agriculture and Natural Resources, University of Maryland, College Park 20742.
authors.forename: A K
authors.initials: AK
authors.lastname: Pradhan
authors.affiliation: New Bolton Center, Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Kennett Square 19348.
authors.forename: R H
authors.initials: RH
authors.lastname: Whitlock
authors.affiliation: Environmental Microbial and Food Safety Laboratory, USDA-Agricultural Research Service, Beltsville, MD 20705.
authors.forename: J S
authors.initials: JS
authors.lastname: Van Kessel
authors.affiliation: Department of Animal and Veterinary Sciences, University of Vermont, Burlington 05405.
authors.forename: J M
authors.initials: JM
authors.lastname: Smith
authors.affiliation: Department of Veterinary and Biomedical Science, Penn State University, University Park 16802.
authors.forename: D R
authors.initials: DR
authors.lastname: Wolfgang
authors.affiliation: Department of Population Medicine and Diagnostic Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY 14850; GD Animal Health, 7400 AA, Deventer, the Netherlands.
authors.forename: Y H
authors.initials: YH
authors.lastname: Schukken
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology / Q000503:physiopathology*; D005243:Feces / Q000382:microbiology; D005260:Female; D016014:Linear Models; D008892:Milk / Q000378:metabolism*; D016927:Mycobacterium avium subsp. paratuberculosis / Q000276:immunology* / Q000302:isolation & purification; D009511:New England / Q000453:epidemiology; D010283:Paratuberculosis / Q000382:microbiology / Q000503:physiopathology*
keywords: Johne’s disease; milk production; paratuberculosis