title: Effects of a 28-day cage-change interval on intracage ammonia levels, nasal histology, and perceived welfare of CD1 mice.
abstract: We measured daily intracage ammonia levels and performed weekly assessments of CD1 male, female, and breeder mice housed within disposable, ventilated cages that remained unchanged for 28 d. We tested housing groups comprising 1, 3, or 5 sex-matched mice per cage and breeder pairs with  litters. Mice housed in cages with higher concentrations of ammonia developed degeneration and inflammatory lesions in the nasal passages. Mean ammonia exposure levels that caused rhinitis were 181 ppm for 18 d. Ammonia exposures of 93 ppm for 16 d caused necrosis of the olfactory epithelium,  whereas 52 ppm for 13 d caused epithelial degeneration. Observers could not detect visible signs of rhinitis or identify cages with elevated ammonia levels, nor did they identify any sick or distressed mice. Observers consistently assigned poorer welfare scores as cages became dirtier. We  conclude that we can extend the cage-change interval to at least 28 d for disposable, ventilated caging housing a single CD1 mouse. Cages containing 3 CD1 mice of either sex should be changed biweekly, and cages containing 5 CD1 mice or breeder pairs should be changed at least once weekly.
authors.affiliation: Stowers Institute for Medical Research, Kansas City, Missouri, USA.
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Vogelweid
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Zapien
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Honigford
authors.forename: Linghui
authors.initials: L
authors.lastname: Li
authors.forename: Hua
authors.initials: H
authors.lastname: Li
authors.forename: Heather
authors.initials: H
authors.lastname: Marshall
mesh_terms: D016902:Air Pollution, Indoor / Q000032:analysis*; D000641:Ammonia / Q000032:analysis* / Q000633:toxicity; D000704:Analysis of Variance; D000818:Animals; D000830:Animals, Laboratory; D004209:Disposable Equipment; D005260:Female; D006799:Housing, Animal / Q000592:standards / Q000706:statistics & numerical data*; D008297:Male; D051379:Mice; D009336:Necrosis / Q000139:chemically induced; D009831:Olfactory Mucosa / Q000187:drug effects / Q000473:pathology*; D013997:Time Factors
chemical_list: D000641:Ammonia