Housing And Husbandry

Beyond3Rs > Research > Housing and Husbandry

We can go Beyond3Rs by focusing on how an animal is housed and cared for.

Laboratory animals spend the vast majority of their lives within their enclosures, rather than in experimental procedures. Aspects of housing and husbandry can profoundly affect both animal well-being and the quality of scientific data produced. Much progress has been made in recent decades, but there are opportunities to continue improving:

The housing environment at minimum should meet all of the physical needs of an animal, allowing them the space to pursue species-specific behaviors.
Environmental enrichment should be provided to give animals the opportunity to demonstrate behavioral agency (i.e., make choices and engage with their environment) and experience improved psychological well-being.
Many animals find handling stressful, and handling stress can have substantial impacts on animal behavior and physiology. Care should be taken to use non-aversive methods whenever possible.
Several aspects of life in a laboratory facility can impact the animals living there. For example, these might include room temperature, smells, vibrations from equipment, exposure to light, loud noises, cage cleaning, and being disturbed while sleeping. Some of these aspects might go unnoticed by humans, but can have profound impacts on animals.
Inadequate housing environments or chronic stress can result in poor well-being, which may impact the validity of scientific outcomes. We are working to further establish how housing and husbandry practices may affect reproducibility and translation.

Refining housing and husbandry not only improves the humaneness of animal research, but mitigates confounding factors which can impact the reliability of results and the validity of animal models. To achieve refinements in housing and husbandry, it is important to promote a culture where we always strive to improve (e.g., by performing regular assessments of programs, and changing practices when presented with new evidence of better methods).

Prioritizing refinements to housing and husbandry takes us Beyond3Rs.

Research: Housing and Husbandry

Optimising reliability of mouse performance in behavioural testing: the major role of non-aversive handling

K. Gouveia, J.L. Hurst, (2017), Scientific Reports

Picking up mice by the tail is aversive, stimulating stress and anxiety. Handling stress can be reduced substantially by using a handling tunnel, or cupping mice without restraint on the open hand. Here the authors use a habituation-dishabituation paradigm in which animals discriminate between two stimuli in successive trials. Tail-handled mice showed little willingness to explore and investigate test stimuli, leading to poor test performance that was only slightly improved by prior familiarisation. Mice handled by tunnel explored readily and showed robust responses to test stimuli regardless of prior familiarisation or stimulus location, though responses were more variable for cup handling. This study shows that non-aversive tunnel handling can substantially improve mouse performance in behavioural tests compared to traditional tail handling.

Conventional laboratory housing increases morbidity and mortality in research rodents: results of a meta-analysis

J. Cait et al. (2022), BMC Biology

Over 120 million mice and rats are used annually in research, conventionally housed in shoebox-sized cages that restrict natural behaviours. This can reduce physical fitness, impair thermoregulation and reduce welfare. In humans, chronic stress has biological costs, increasing disease risks and potentially shortening life. This meta-analysis therefore tested the hypothesis that, compared to rodents in ‘enriched’ housing that better meets their needs, conventional housing increases stress-related morbidity and all-cause mortality. The hypothesis was supported: conventional housing significantly exacerbated disease severity (cancer, stroke, depression, cardiovascular disease, signs of anxiety) with medium to large effect sizes. Conventional housing appears sufficiently distressing to compromise rodent health, raising ethical and scientific concerns.

Stressed out: providing laboratory animals with behavioral control to reduce the physiological effects of stress

B.N. Gaskill, J.P. Garner (2017), Lab Animal

Laboratory animals experience a large amount of environmental stress. Chronic uncontrollable stress is widely acknowledged for its negative alterations to physiology. However, there is a lack in the understanding of how the laboratory environment affects animal physiology and behavior, particularly as it relates to characteristics of the human disease being modeled. Given the evidence on how stressors affect physiology, it is clear that efforts to model human physiology in animal models must consider animal stress as a confounding factor. We present evidence illustrating that providing captive animals with control or predictability is the best way to reduce the negative physiological effects of these difficult-to-manage stressors.

Do we still need a canary in the coal mine for laboratory animal facilities? A systematic review of environmental health monitoring versus soiled bedding sentinels

M.R. LaFollette et al. (2024), PLOS One

Despite increasing evidence that Environmental Health Monitoring (EHM) is an effective method to perform rodent colony health surveillance, promotes the 3Rs, and is comparable or reduces costs and labor, many research institutions continue to use live Soiled Bedding Sentinels (SBS). Those responsible for rodent colony health monitoring may remain cautious of the evidence supporting this new technology. This formal systematic review to identified and analyzed the research on the efficacy of EHM as compared to SBS. All types of EHM appear to be superior to soiled bedding sentinels at detecting pathogens. There is a strong evidence base supporting the replacement of SBS with EHM.

Nest Building as an Indicator of Health and Welfare in Laboratory Mice

B.N. Gaskill et al. (2013), JOVE

The minimization and alleviation of suffering has moral and scientific implications. In order to mitigate this negative experience one must be able to identify when an animal is actually in distress. Pain, illness, or distress cannot be managed if unrecognized. The observation of nesting behavior shows promise as the basis of a species appropriate cage-side assessment tool for recognizing distress in mice. Here we demonstrate the utility of nest building behavior in laboratory mice as an ethologically relevant indicator of welfare. The methods presented can be successfully used to identify thermal stressors, aggressive cages, sickness, and pain. Observation of nest building behavior in mouse colonies provides a refinement to health and well-being assessment.

The critical issue for well-being and model quality is control, not of the animal, but by the animal. Through over-engineering animal housing we take away an animal's control of its environment, which in turn makes it fundamentally abnormal.

From "Introducing Therioepistomology"

Behavioral or nutritional drive: which motivation affects rates of food grinding in CD1 mice?

B.N. Gaskill et al. (2025), Applied Animal Behaviour

Some laboratory mice gnaw their food into a powder which they do not ingest. The ground-up food fills the cage, resulting in miscalculations of food consumption, welfare issues, and economic issues of food wastage. This study sought to determine if the motivation behind food grinding was related to a mouse’s innate behavioral drive to gnaw or rather a nutritional drive to seek out macronutrient components in the feed. High fat treatments (either shell-on sunflower seeds or a diet with macronutrient equivalence to a sunflower kernel), but not the method of delivery, decreased the amount of ground food produced per cage. This study replicated previous results which found differences in the composition of the gnawed feed in comparison to the original diet, supporting the hypothesis that food grinding behavior is driven by a nutritional motivation, not a behavioral one.

Effects of Cage Enrichment on Behavior, Welfare and Outcome Variability in Female Mice

J.D. Bailoo et al. (2018), Frontiers in Behavioral Neuroscience

Common laboratory mouse housing conditions are associated with indicators of impaired welfare. Due to concerns that more complex environmental conditions might increase variation in experimental results, there has been considerable resistance to the implementation of environmental enrichment beyond the provision of nesting material. Here, the authors systematically varied environmental enrichment across four levels. The greatest benefit was observed in animals housed with the greatest degree of enrichment: stereotypic behavior, anxiety, growth and stress physiology varied in a manner consistent with improved animal welfare compared to the housing conditions with less enrichment. There was no indication that environmental enrichment increased variation in experimental results.

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