Herd-level factors associated with isolation of Salmonella in a multi-state study of conventional and organic dairy farms I. Salmonella shedding in cows C.P. Fossler a, * , S.J. Wells a , J.B. Kaneene c , P.L. Ruegg d , L.D. Warnick e , J.B. Bender a , L.E. Eberly b , S.M. Godden a , L.W. Halbert c a University of Minnesota, College of Veterinary Medicine, 1354 Eckles Avenue, St. Paul, MN 55108, USA b University of Minnesota, Division of Biostatistics, School of Public Health, 420 Delaware St. SE, MMC 303, Minneapolis, MN 55455, USA c The Population Medicine Center, A 109 VMC, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA d University of Wisconsin, Department of Dairy Science, 1675 Observatory Dr., Madison, WI 53706, USA e Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA Received 3 June 2004; received in revised form 1 February 2005; accepted 8 April 2005 Abstract The objective of this study was to evaluate associations between herd characteristics and the isolation of Salmonella from dairy cows in Minnesota, Wisconsin, Michigan, and New York. Study farms were 129 conventional and organic farms enrolled without regard to previous history of Salmonella infection. Herds were sampled at 2-month intervals over a 1-year period. This is the largest study to date on Salmonella shedding in dairy cows and the only study evaluating herd- www.elsevier.com/locate/prevetmed Preventive Veterinary Medicine 70 (2005) 257–277 DOI of original article: 10.1016/j.prevetmed.2005.04.002. * Corresponding author. Present address: National Surveillance Unit, Centers for Epidemiology and Animal Health, USDA, APHIS, VS, 2150 Centre Ave., Bldg. B, Mail Stop 2E7, Fort Collins, CO 80526-8117, USA. Tel.: +1 970 494 7595; fax: +1 970 494 7229. E-mail address: charles.p.fossler@aphis.usda.gov (C.P. Fossler). 0167-5877/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.prevetmed.2005.04.003