The Role of Emotional Contagion in the Distress Exhibited by Grouped Mice Exposed to CO2.

The 2013 AVMA Guidelines for the Euthanasia of Animals recommends a chamber volume displacement rate of 10% to 30% per minute (v/min) when euthanizing small laboratory rodents with CO2. Group euthanasia of mice is a common practice, and grouping strangers is often avoided to minimize distress; however, emotional contagion, which occurs between familiar animals but not strangers, has not been studied in the context of group CO2 euthanasia. This study examined cagemate- and stranger-grouped mice exposed to 10%, 30%, or 50% v/min CO2 to determine whether emotional contagion plays a role in this context and whether that role is influenced by CO2 flow rate. Videos of adult male C57BL/6J mice exposed to different CO2 flow rates were scored for durations of dyspnea, ataxia, and consciousness as well as the numbers of face pawing and jump behaviors. Blood was collected at time of unconsciousness and assayed for ACTH. Cagemates experienced significantly longer durations of conscious dyspnea and ataxia with 10% v/min CO2 compared with 30% and 50% v/min. Similarly, strangers experienced significantly longer duration of conscious dyspnea with 10% v/min CO2 compared with 30% and 50% v/min and significantly longer duration of ataxia with 10% compared with 50% v/min. Cagemates showed significantly more jumps with 10% v/min CO2 compared with 30% and 50% v/min, whereas jumping was unaffected by CO2 flow rate in strangers. We conclude that more potential for distress exists when cagemate and stranger mice are exposed to a 10% v/min CO2 flow rate and that emotional contagion may contribute to distress in cagemates at this flow rate. Therefore, we propose that 30% v/min CO2 should be used for euthanasia of mice, and that 50% v/min should also be considered humane.

Sterility and Stability of Diluted Meloxicam in Compounded Multi-dose Vial after 365 Days.

Meloxicam is a common analgesic for rodents. Because meloxicam is only formulated commercially for companion animals, it requires dilution to achieve doses appropriate for small, laboratory species. Compounded multidose vial (cMDV) are often created to dilute and store a diluted drug. However, chronic cMDV use runs the risk of contamination and becoming a potential source of nosocomial infection. In this study, we created 15 cMDV by diluting meloxicam with sterile water (dilution, 1:10). cMDV were punctured once daily for 30 d. To determine the sterility of the diluted meloxicam, we assessed 8 cMDV for bacterial growth on days 0, 10, 20, 30, and 365 and tested them for endotoxin on days 0, 30, and 365. In addition, the stability of the remaining 7 cMDV was assessed on days 0, 10, 20, 30, and 365, by using liquid chromatography-diode assays. No bacterial growth or endotoxin was detected at any time point, and the drug concentrations remained stable over 365 d. Given the results this study, we believe that cMDV of diluted meloxicam can remain sterile and stable for 365 d.