title: Lighting during grow-out and Salmonella in broiler flocks.
abstract: BACKGROUND
  Lighting is used during conventional broiler grow-out to modify bird behaviour to reach the goals of production and improve bird welfare. The protocols for lighting intensity vary. In a field study, we evaluated if the lighting practices impact the burden of Salmonella in broiler flocks.
  
  
  METHODS
  Conventional grow-out flocks reared in the states of Alabama, Mississippi and Texas, USA in 2003 to 2006 were sampled 1 week before harvest (n = 58) and upon arrival for processing (n = 56) by collecting feathered carcass rinsate, crop and one cecum from each of 30 birds, and during processing by collecting rinsate of 30 carcasses at pre-chilling (n = 56) and post-chilling points (n = 54). Litter samples and drag swabs of litter were collected from the grow-out houses after bird harvest (n = 56). Lighting practices for these flocks were obtained with a questionnaire completed by the growers. Associations between the lighting practices and the burden of Salmonella in the flocks were tested while accounting for variation between the grow-out farms, their production complexes and companies.
  
  
  RESULTS
  Longer relative duration of reduced lights during the grow-out period was associated with reduced detection of Salmonella on the exterior of birds 1 week before harvest and on the broiler carcasses at the post-chilling point of processing. In addition, starting reduced lights for > or = 18 hours per day later in the grow-out period was associated with decreased detection of Salmonella on the exterior of broilers arriving for processing and in the post-harvest drag swabs of litter from the grow-out house.
  
  
  CONCLUSIONS
  The results of this field study show that lighting practices implemented during broiler rearing can impact the burden of Salmonella in the flock. The underlying mechanisms are likely to be interactive.
authors.affiliation: Epidemiology group, Centre for Infectious Diseases, University of Edinburgh, R. 138, Ashworth Laboratories, Kings Buildings, West Mains Road, Edinburgh, EH9 3JT, UK. Victoriya.Volkova@ed.ac.uk
authors.forename: Victoriya V
authors.initials: VV
authors.lastname: Volkova
authors.forename: J Allen
authors.initials: JA
authors.lastname: Byrd
authors.forename: Sue Ann
authors.initials: SA
authors.lastname: Hubbard
authors.forename: Danny
authors.initials: D
authors.lastname: Magee
authors.forename: Richard H
authors.initials: RH
authors.lastname: Bailey
authors.forename: Robert W
authors.initials: RW
authors.lastname: Wills
mesh_terms: D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D002432:Cecum / Q000382:microbiology; D002645:Chickens; D003426:Crop, Avian / Q000382:microbiology; D008029:Lighting / Q000379:methods*; D016015:Logistic Models; D011201:Poultry Diseases / Q000382:microbiology*; D011446:Prospective Studies; D012475:Salmonella / Q000254:growth & development*; D012481:Salmonella Infections, Animal / Q000382:microbiology*; D011795:Surveys and Questionnaires