Validation of Sanitization Practices in Single-use Individually Ventilated Mouse Cages at Standard and Thermoneutral Temperatures.

Vivarium husbandry practices are based on performance data and adhere to applicable regulatory guidelines. Refinements in husbandry and optimization of sanitization protocols improve animal wellbeing and help standardize the microenvironment, contributing to research reproducibility. The objective of this study was to evaluate the microenvironment to establish performance standards for mouse husbandry and sanitization, including housing at standard and thermoneutral temperatures. Male C57BL/6J mice were housed singly and in groups in disposable IVCs on α-cellulose or corncob bedding and microenvironmental indicators (ammonia, carbon dioxide) were evaluated. In addition, microbial bioburden tests (ATP and RODAC) were performed on cages and cage accessories on days 0, 7, 14 and, 28 to 30 after cage change. Water testing and aerobic culture of the waterspout of bottles containing chlorinated water were performed to determine acceptable replacement schedules. Ammonia levels remained below the National Institute of Occupational Safety and Health 8-h recommended exposure limit for humans (25 ppm) at all time points for all housing conditions through day 21 for group-housed mice, and through day 30 for singly housed mice. Microbial bioburden results for cage accessories and water testing were acceptable up to 28 d after cage change (RODAC less than 50 CFU; ATP less than 100,000 RLU) at both standard and thermoneutral housing temperatures. Mice remained clinically healthy throughout the studies. These results support site operating practices and verify extended sanitization recommendations per the Guide of the Care and Use of Laboratory Animals in this disposable IVC environment: group-housed mice receive bottom cage and water bottle change up to every 14 d with full cage change (including lid and accessories) every 28 d, and singly housed mice receive full cage change every 28 to 30 d or sooner.

Automated monitoring of respiratory rate as a novel humane endpoint: A refinement in mouse metastatic lung cancer models.

In oncology research, while xenograft tumor models are easily visualized and humane endpoints can be clearly defined, metastatic tumor models are often based on more subjective clinical observations as endpoints. This study aimed at identifying objective non-invasive criteria for predicting imminent distress and mortality in metastatic lung tumor-bearing mice. BALB/c and C57BL/6 mice were inoculated with CT26 or B16F10 cells, respectively. The mice were housed in Vium smart cages to continuously monitor and stream respiratory rate and locomotion for up to 28 days until scheduled euthanasia or humane endpoint criteria were met. Body weight and body temperature were measured during the study. On days 11, 14, 17 and 28, lungs of subsets of animals were microCT imaged in vivo to assess lung metastasis progression and then euthanized for lung microscopic evaluations. Beginning at day 21, most tumor-bearing animals developed increased respiratory rates followed by decreased locomotion 1-2 days later, compared with the baseline values. Increases in respiratory rate did not correlate to surface tumor nodule counts or lung weight. Body weight measurement did not show significant changes from days 14-28 in either tumor-bearing or control animals. We propose that increases in respiratory rate (1.3-1.5 X) can be used to provide an objective benchmark to signal the need for increased clinical observations or euthanasia. Adoption of this novel humane endpoint criterion would allow investigators time to collect tissue samples prior to spontaneous morbidity or death and significantly reduce the distress of mice in the terminal stages of these metastatic lung tumor models.