Mexas Angela M, Brice Angela K, Caro Adam C, Hillanbrand Troy S, Gaertner Diane J
University Laboratory Animal Resources, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Office of Animal Welfare, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
J Am Assoc Lab Anim Sci. 2015 Sep;54(5):478-86.
Many factors influence ammonia levels in rodent cages, and high intracage ammonia has been associated with specific types of abnormal nasal pathology in mice. The use of autoclaved corncob bedding and the maintenance of low room humidity reduce the accumulation of ammonia in mouse cages. However, there are no engineering standards that define the limits of ammonia exposure for mice housed in static isolation cages. Regulatory guidance indicates that solid bottom cages must be sanitized at least weekly and that cage components in direct contact with animals must be sanitized at least every 2 wk. Common practice is to replace the bottoms and bedding of static isolation cages once weekly. To determine whether changing static isolation cages once weekly is an appropriate performance standard for mice, we prospectively evaluated the relationship between ammonia levels, nasal histopathology, and housing densities in various grouping strategies of mice housed in static isolation cages. Here, we report that the average nasal pathology score per cage and intracage ammonia levels were correlated, but nasal pathology scores did not differ among mice housed in breeding pairs, breeding trios, or female groups. In light of ammonia levels and histopathology scores as performance standards, these results suggest that a weekly cage-change frequency for static isolation cages does not result in adverse effects. Our results provide evidence to support current practices in the use of static isolation cages for housing laboratory mice in modern vivaria.
许多因素会影响啮齿动物饲养笼内的氨水平，而笼内高氨水平已与小鼠特定类型的异常鼻腔病理状况相关联。使用经高压灭菌的玉米芯垫料以及保持较低的室内湿度可减少小鼠饲养笼内氨的积累。然而，对于饲养在静态隔离笼中的小鼠，尚无界定氨暴露限值的工程标准。监管指南指出，实心底部的笼子必须至少每周消毒一次，且与动物直接接触的笼子组件必须至少每两周消毒一次。通常的做法是每周更换一次静态隔离笼的底部和垫料。为了确定每周更换一次静态隔离笼对小鼠而言是否为合适的性能标准，我们前瞻性地评估了饲养在静态隔离笼中的小鼠在不同分组策略下氨水平、鼻腔组织病理学和饲养密度之间的关系。在此，我们报告称，每个笼子的平均鼻腔病理评分与笼内氨水平相关，但饲养在繁殖对、繁殖三联组或雌性组中的小鼠的鼻腔病理评分并无差异。鉴于氨水平和组织病理学评分作为性能标准，这些结果表明，静态隔离笼每周更换笼子的频率不会产生不利影响。我们的结果为支持现代动物饲养设施中使用静态隔离笼饲养实验小鼠的当前做法提供了证据。
