title: Cage change intervals for opossums (Monodelphis domestica) in individually ventilated cages.
abstract: The opossum Monodelphis domestica is the most commonly used marsupial in biomedical research. At our institution, these opossums are housed in polycarbonate (35.6 cm × 25.4 cm × 17.8 cm) individually ventilated cages. Previous studies of the cage microenvironment  of rodents housed in individually ventilated cages have demonstrated that the cage-change frequency could be extended from 7 to 14 d, without detriment to the animals' wellbeing. We sought to determine whether the cage change frequency for opossums housed in individually ventilated cages could  be extended to 14 d. Opossums were placed into 3 experimental groups: singly housed males, singly housed females, and females housed with litters. The 14-d testing period was repeated twice, with temperature, relative humidity, and ammonia levels tested on days 0, 7, and 14. Acceptable ranges  for the cage microenvironment were based on standards followed by our institution for housing rodents: temperature between 22 to 26 °C, relative humidity between 30% to 70%, and ammonia less than 25 ppm. Throughout both 14-d testing periods, temperature, relative humidity, and ammonia  levels for singly housed male and singly housed female opossums were within acceptable ranges. However, ammonia levels exceeded the recommended 25 ppm on day 7 of both testing periods for female opossums housed with litters. In summary, the cage-change frequency for a singly housed opossum  in an individually ventilated cage can be extended to 14 d.
authors.affiliation: Division of Animal Resources, University of Illinois at Urbana-Champaign, Urbana, IL, USA. allison3@illinois.edu
authors.forename: Sarah O
authors.initials: SO
authors.lastname: Allison
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Criley
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Kim
authors.forename: Lyndon J
authors.initials: LJ
authors.lastname: Goodly
mesh_terms: D016902:Air Pollution, Indoor / Q000032:analysis*; D000641:Ammonia / Q000032:analysis; D000827:Animal Welfare; D000818:Animals; D000830:Animals, Laboratory; D005260:Female; D006799:Housing, Animal; D006813:Humidity; D007756:Laboratory Animal Science / Q000379:methods*; D008297:Male; D048309:Monodelphis; D013696:Temperature; D013997:Time Factors; D014691:Ventilation / Q000379:methods
chemical_list: D000641:Ammonia