Exposure to soiled bedding reduces abnormal repetitive behaviors in mice
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Karin Müller1, Theresia Lengheimer2, Julia B Kral-Pointner3
1Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria.
Abstract:
Hygiene management protocols in laboratory mouse husbandries worldwide most commonly employ soiled bedding-exposed sentinel mice to monitor the occurrence of infections in mouse colonies. Using this approach, sentinel mice repeatedly receive a mixture of used bedding, supplied by a variety of cages of a defined hygienic unit for a period of several months. Hereby, microorganisms shed in the used bedding can infect the sentinel animals and can be detected in subsequent health monitoring procedures. However, murine excrements carry more than only microorganisms. Mouse feces and urine also contain a multitude of olfactory molecules, which the animals use to code information about social status and context. However, if and how the persistent and repeated experience with these odor cues affects the behavior of sentinel mice, has not yet been explored. To address this question, we conducted a longitudinal study for neurochemical output parameters related to an organism's responsiveness to challenging conditions, and for the exploratory assessment of a panel of home cage behaviors in soiled bedding and control female C57BL/6J mice. We found that the number of mice showing abnormal repetitive behaviors, including barbering and bar mouthing, was lower in the soiled bedding group. While neutrophil/lymphocyte ratios and fecal corticosterone metabolites did not differ between groups, the within-group variance of the neutrophil/lymphocyte ratio was reduced in the soiled bedding group. These results show that the occurrence of abnormal repetitive behaviors is lower in sentinel than in control mice and suggest a beneficial effect of soiled bedding on the welfare of laboratory mice and on outcome variability.
Insights
Laboratory mice exposed to soiled bedding showed fewer abnormal repetitive behaviors, suggesting this practice may improve animal welfare and reduce outcome variability in research. This highlights a potential benefit for sentinel mouse monitoring.
Area of Science:
- Animal Welfare Science
- Laboratory Animal Science
- Behavioral Neuroscience
Background:
- Sentinel mice are commonly used in laboratory animal facilities to monitor for infections via soiled bedding exposure.
- Murine excreta contain olfactory cues crucial for social signaling, but their impact on sentinel mice behavior is unexplored.
- Understanding these olfactory influences is key to refining animal husbandry and experimental design.
Purpose of the Study:
- To investigate the longitudinal effects of soiled bedding exposure on the behavior and neurochemical parameters of laboratory mice.
- To assess how persistent exposure to olfactory cues in soiled bedding influences abnormal repetitive behaviors and stress indicators.
- To determine if soiled bedding exposure impacts the welfare and outcome variability in research settings.
Main Methods:
- A longitudinal study was conducted on female C57BL/6J mice, comparing a soiled bedding exposure group with a control group.
- Behavioral assessments included monitoring for abnormal repetitive behaviors such as barbering and bar mouthing.
- Neurochemical output parameters and neutrophil/lymphocyte ratios were analyzed to assess stress and physiological responses.
Main Results:
- Mice exposed to soiled bedding exhibited a lower incidence of abnormal repetitive behaviors compared to controls.
- No significant differences were observed in neutrophil/lymphocyte ratios or fecal corticosterone metabolites between the groups.
- A reduced within-group variance in the neutrophil/lymphocyte ratio was noted in the soiled bedding group.
Conclusions:
- Soiled bedding exposure in laboratory mice is associated with a reduction in abnormal repetitive behaviors, indicating a potential welfare benefit.
- This practice may contribute to more consistent experimental outcomes by reducing behavioral and physiological variability.
- The findings suggest that soiled bedding exposure could be a valuable tool for enhancing laboratory animal welfare and research reproducibility.
