Invention of a Forced-air-ventilated Micro-isolation Cage and Rack System

—Environment within Cages: Temperature and Ammonia Concentration—

Abstract

There is little information about microenvironments within laboratory animal cages, although several guidelines on the macroenvironment in laboratory animal rooms have been reported. We have developed a forced-air ventilation system (FVMIS) to improve laboratory animal wellbeing. In this study, we tested the performance of the FVMIS in terms of temperature and ammonia concentration within cages. Continuous measurement of temperature and ammonia concentration was carried out in FVMIS cages housing 5 rats each. The average temperature within the cages was 22°C to 24°C, and the temperature difference among cages was 0.93°C. The air exchange rate used was 65 changes per hour. FVMIS was capable of controling the temperature within cages uniformly and accurately with a lower air exchange rate than with the conventional system. The ammonia concentration reached 20 ppm within 9 days in a filtercapped conventional cage, but took 13 to 16 days to reach 20 ppm with FVMIS. It appears that FVMIS is capable of suppressing the ammonia concentration increase in cages, thereby reducing the frequency of cage changes and the stress to laboratory animals when cages are changed. In the present study, it was confirmed that FVMIS contributes not only to microenvironmental control in terms of temperature and ammonia concentration with a lower air exchange rate, but also to animal wellbeing.