title: Water activity of poultry litter: Relationship to moisture content during a grow-out.
abstract: Poultry grown on litter floors are in contact with their own waste products. The waste material needs to be carefully managed to reduce food safety risks and to provide conditions that are comfortable and safe for the birds. Water activity (Aw) is an important thermodynamic property that has been shown to be more closely related to microbial, chemical and physical properties of natural products than moisture content. In poultry litter, Aw is relevant for understanding microbial activity; litter handling and rheological properties; and relationships between in-shed relative humidity and litter moisture content. We measured the Aw of poultry litter collected throughout a meat chicken grow-out (from fresh pine shavings bedding material to day 52) and over a range of litter moisture content (10-60%). The Aw increased non-linearly from 0.71 to 1.0, and reached a value of 0.95 when litter moisture content was only 22-33%. Accumulation of manure during the grow-out reduced Aw for the same moisture content. These results are relevant for making decisions regarding litter re-use in multiple grow-outs as well as setting targets for litter moisture content to minimise odour, microbial risks and to ensure necessary litter physical conditions are maintained during a grow-out. Methods to predict Aw in poultry litter from moisture content are proposed.
authors.affiliation: Department of Agriculture and Fisheries, Queensland Government, Toowoomba, Qld 4350, Australia; University of New South Wales, School of Civil and Environmental Engineering, Sydney, NSW 2052, Australia; Poultry CRC, PO Box U242, University of New England, Armidale, NSW 2351, Australia. Electronic address: mark.dunlop@daf.qld.gov.au.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Dunlop
authors.affiliation: Department of Agriculture and Fisheries, Queensland Government, Toowoomba, Qld 4350, Australia.
authors.forename: Jim
authors.initials: J
authors.lastname: McAuley
authors.affiliation: Poultry CRC, PO Box U242, University of New England, Armidale, NSW 2351, Australia; The University of Queensland, Queensland Alliance for Agriculture and Food Innovation, St Lucia, Brisbane 4067, Australia.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Blackall
authors.affiliation: University of New South Wales, School of Civil and Environmental Engineering, Sydney, NSW 2052, Australia.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Stuetz
mesh_terms: D000818:Animals; D002645:Chickens; D005430:Floors and Floorcoverings; D006799:Housing, Animal; D008372:Manure / Q000382:microbiology; D064307:Microbiota; D011200:Poultry; D012212:Rheology; D014867:Water / Q000032:analysis*
chemical_list: D008372:Manure; D014867:Water
keywords: Broiler; Equilibrium relative humidity (ERH); Meat chicken; Water absorption isotherms; Wet litter