Fecal shedding of Salmonella spp. by dairy cows on farm and at cull cow markets

As part of a national study of the U,S. dairy cow population, fecal samples were collected from representative cows on 91 dairies and 97 cull dairy co w markets in 19 states. Salmonella spp. were recovered from 5.4% of milk co ws, 18.1% of milk cows expected to be culled within 7 days, and 14.9% of cu lled dairy cows at markets. On a premise basis, Salmonella shedding in milk cows was detected on 21.1% of dairies and 66% of cull dairy cow markets. T he percentage of herds with at least one cow with detectable Salmonella fec al shedding was higher during the sampling period from May through July, in herds with at least 100 milk cows, and in herds in the South region. The m ost common Salmonella serogroups isolated were E (30.8% of isolates) and C1 (28.6%); the most common serotypes isolated were Salmonella Montevideo (21 .5% of isolates), Salmonella Cerro (13,3%), and Salmonella Kentucky (8.5%). Fecal shedding of Salmonella Typhimurium or Salmonella Typhimurium var. co penhagen was infrequent (2.8% of isolates). Most isolates (88.9%) were susc eptible to all 17 antimicrobials evaluated; multiple resistance was an infr equent occurrence. This study provides information describing the distribut ion of Salmonella fecal shedding from dairy cows on farm and at markets and will serve as a baseline for future studies.