Breaking up is hard to do: Does splitting cages of mice reduce aggression?

Blankenberger, Whitney B.; Weber, Elin M.; Chu, David K; Geronimo, Jerome T.; Theil, Jacob H; Gaskill, Brianna N.; Pritchett-Corning, Kathleen R.; Albertelli, Megan A.; Garner, Joseph P.; Ahloy‐Dallaire, Jamie

doi:10.1016/j.applanim.2018.06.003

Cited by 8 publications

(5 citation statements)

References 26 publications

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“…It is preferable to avoid single-housing and to maintain mice in groups where possible. One possibility to avoid isolating the presumed aggressor could be to split groups of mice experiencing aggression into two smaller subgroups, which has been supported by recent research 46 . A controlled study investigating different actions that could be taken would help provide further insight and guidance for minimising further aggression.…”

Section: Discussionmentioning

confidence: 99%

Cage aggression in group-housed laboratory male mice: an international data crowdsourcing project

Lidster

Owen

Browne

et al. 2019

Sci Rep

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Aggression in group-housed laboratory mice is a serious animal welfare concern. Further understanding of the causes of mouse aggression could have a significant impact on a large number of laboratory animals. The NC3Rs led a crowdsourcing project to collect data on the prevalence and potential triggers of aggression in laboratory mice. The crowdsourcing approach collected data from multiple institutions and is the first time such an approach has been applied to a laboratory animal welfare problem. Technicians observed group-housed, male mice during daily routine cage checks and recorded all incidents of aggression-related injuries. In total, 44 facilities participated in the study and data was collected by 143 animal technicians. A total of 788 incidents of aggression-related injuries were reported across a sample population of 137,580 mice. The mean facility-level prevalence of aggression-related incidents reported across facilities was equivalent to 15 in 1,000 mice. Key factors influencing the prevalence of aggression included strain; number of mice per cage; how mice were selected into a cage; cage cleaning protocols; and transfer of nesting material. Practical recommendations have been provided to minimise aggressive behaviour in group-housed, male mice based upon the results of the study and taking into consideration the current published literature.

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Section: Discussionmentioning

confidence: 99%

Cage aggression in group-housed laboratory male mice: an international data crowdsourcing project

Lidster

Owen

Browne

et al. 2019

Sci Rep

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“…Stress, injuries and death following aggression, make this an important animal welfare issue with direct implications on the 3Rs. As a consequence of aggression, groups of male mice are frequently split into smaller groups, single-housed or euthanized [7]. Sometimes, male mice are also single-housed to prevent aggression.…”

Section: Discussionmentioning

confidence: 99%

“…Aggression within the homecage is one of the most common husbandry problems encountered, with wounding being the second most common clinical condition in mice [6]. When groups of mice are observed fighting excessively, or animals are found wounded, groups are generally separated and individuals can be euthanized or housed individually [7]. Not only is aggression a concern for animal welfare; pain, stress, and social isolation can also alter a number of physiological parameters, creating variability and jeopardizing scientific validity [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Group and Single Housing of Male Mice: Collected Experiences from Research Facilities in Sweden

Zidar

Weber

Ewaldsson

et al. 2019

Animals

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Simple Summary:The mouse is the most commonly used mammal in scientific research, and housed in research facilities around the world. Mice are a social species, but when housing male mice together in a confined environment in the laboratory, aggression is often observed and can be problematic. Fighting or trying to avoid fighting can be stressful. Furthermore, fighting can lead to injuries which can sometimes be fatal. Mouse aggression is therefore a significant welfare problem and has implications on the 3Rs (Replacing, Reducing, and Refining animal use in scientific procedures and education). In this study, we used a survey and workshops to collect the experiences of animal technicians, veterinarians, and researchers at Swedish research animal facilities relating to mouse aggression and what methods of preventing aggression they practice. Both group housing and single-housing as a consequence of aggression was perceived as problematic and stressful for the animals. In line with current recommendations from the literature, participants perceived that aggression occurred less if mice were grouped with litter mates at an early age, that nesting material was transferred at cage cleaning, and disturbance was kept to a minimum. Experience from practice will play a valuable part in developing guidelines for group-housed male mice.Abstract: Animals used for scientific purposes are protected by EU legislation. Social animals should be kept in stable groups that enable species-typical social behavior and provide individuals with social comfort. However, when group-housing male mice, aggression within the homecage is a common husbandry and welfare problem. Excessive fighting and injuries due to aggression can cause pain and stress, resulting in individuals being euthanized or housed individually. In addition, stress can alter physiological parameters, risking scientific validity and generating larger sample sizes. Mouse aggression, and the consequences thereof, thus opposes the 3R goals of Refining the methods to Animals 2019, 9, 1010 2 of 24 minimize potential pain and suffering and Reducing the number of animals used. Animal technicians, veterinarians, and scientists using animals have valuable information on how these problems are experienced and handled in practice. We assembled these experiences from laboratory animal facilities in Sweden, mapping problems observed and identifying strategies used to prevent mouse aggression. In line with current literature, less aggression was perceived if mice were grouped before sexual maturity, re-grouping avoided and nesting material transferred at cage cleaning. Preventing aggression will minimize pain and suffering and enable housing of stable groups, leading to more reliable scientific outcomes and is thus of high 3Rs relevance.

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“…Mice were inspected for wounds daily at cage checks and individually once per week during cage changes. Each mouse was given a score ranging from 0–5, as defined by [ 41 ]. Briefly, if a mouse was given a score 1, it was monitored daily to see if wounding escalated.…”

Section: Methodsmentioning

confidence: 99%

The impact of cage dividers on mouse aggression, dominance and hormone levels

Streiff,

Herrera,

Voelkl

et al. 2024

PLoS ONE

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Home cage aggression in group-housed male mice is a major welfare concern and may compromise animal research. Conventional cages prevent flight or retreat from sight, increasing the risk that agonistic encounters will result in injury. Moreover, depending on social rank, mice vary in their phenotype, and these effects seem highly variable and dependent on the social context. Interventions that reduce aggression, therefore, may reduce not only injuries and stress, but also variability between cage mates. Here we housed male mice (Balb/c and SWISS, group sizes of three and five) with or without partial cage dividers for two months. Mice were inspected for wounding weekly and home cages were recorded during housing and after 6h isolation housing, to assess aggression and assign individual social ranks. Fecal boli and fur were collected to quantify steroid levels. We found no evidence that the provision of cage dividers improves the welfare of group housed male mice; The prevalence of injuries and steroid levels was similar between the two housing conditions and aggression was reduced only in Balb/c strain. However, mice housed with cage dividers developed less despotic hierarchies and had more stable social ranks. We also found a relationship between hormone levels and social rank depending on housing type. Therefore, addition of cage dividers may play a role in stabilizing social ranks and modulating the activation of hypothalamic–pituitary–adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes, thus reducing phenotypic variability between mice of different ranks.

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Breaking up is hard to do: Does splitting cages of mice reduce aggression?

Cited by 8 publications

References 26 publications

Cage aggression in group-housed laboratory male mice: an international data crowdsourcing project

Cage aggression in group-housed laboratory male mice: an international data crowdsourcing project

Group and Single Housing of Male Mice: Collected Experiences from Research Facilities in Sweden

The impact of cage dividers on mouse aggression, dominance and hormone levels

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