When selecting animal models for conducting scientific research, welfare should be the main priority. This article considers the effects of different housing strategies for mice and how PhenoTyper offers researchers insight into animal well-being.
There is clearly a considerable ethical argument for optimizing the well-being of animals used in research. William Russel and Rex Burch infamously made this case in their 1952 paper The Principles of Humane Experimental Technique, in which they offered a blueprint for the considerations of animal welfare in science.1
The value of eliminating any unnecessary suffering and distress in animals should be readily apparent to most. But the argument for animal welfare extends much further than this.
A significant volume of research demonstrates that animals whose well-being is endangered are more likely to present physiological and behavioral abnormalities.2,3 Therefore, carefully controlling all factors that contribute to an animal’s well-being – insofar as those that can be evaluated – should be the guiding principle to guarantee experimental validity.
Image Credit: Shutterstock/unoL
The importance of housing
Since the most frequently used animal models are mice in biomedical research, maximizing their well-being is crucial. The housing that mice are kept in plays a key role in this.
Naturally, mice are animals, so it is generally advised that when possible (and partible) they should be housed in groups.4
However, inter-male aggression is a major welfare concern for mice housed in captivity when it is not possible for them to escape each other as male mice do not naturally share territories.5 This means that paired housing or single housing is often a more feasible choice.
Other contributing factors – experimental design and disease control in particular – also make single housing a preferred choice in many cases. There are those that advocate for the use of cage dividers that allow sensory but not physical contact between neighboring mice to enable some level of social interaction.6
The immediate effects of housing on mice’s well-being, behavior and physiology are still up for debate. However, research shows that the single housing of mice is associated with various physiological ailments.
These include a reduction in growth rates and reduced lean body mass during growth, increased predisposition to obesity in adulthood and raised levels of visceral adipose tissue mass.7,8
Behavior can be influenced by housing too. Single-housed mice are known to exhibit anxiety- and depressive-like behaviors as well as broken cognitive function when compared to pair- or group-housed mice – although these effects are also dependent on a range of other environmental and physiological factors.9–11
“Separated pair” housing using cage dividers seems to have some contrast in behavioral and locomotor performance when compared to single housing – although it is not completely clear whether this corresponds with a difference in well-being.
Ideally, all of these changes should be considered in the research goals of experimenters using mice models.
Choosing the optimal housing strategy for your experiment
In the long term, housing conditions tend to be at the mercy of experimental parameters. For instance, to prevent mice from damaging each other’s cannulas, single housing is mandatory for studies involving the cannulation of mice.12
Studies of energy balance regulation also tend to drift towards single housing so that the food intake and thermal profiles of each mouse can be carefully monitored. Single housing in individually vented cage (IVC) systems can also help prevent disease transmission between the mice.
Still, considering whether experimental parameters could permit paired (or separated pair) housing is useful if wanting to reduce stress, accomplish longer testing periods, and enhance experimental validity.
A number of experiments involve testing mice in a special environment away from their housing – however, testing them in their home environment offers another chance to reduce stress levels and eradicate the confounding effects of a change in environment.13
Evaluating the effects of housing paradigms on mice
Housing can have significant behavioral and physiological effects on mice: phenotypically, socially housed mice are not the same animal as mice that have been individually housed.
Observing animals in their home cage and comparing their behavior throughout the experiments is vital to understanding the effects of various housing paradigms.
So, whether opting for social or separate housing, it is essential to make sure everything is carefully considered and that a scoring system is in place.
PhenoTyper is a fully integrated and automated cage monitoring system. By facilitating simple monitoring of individual animals in their home cage, PhenoTyper offers researchers access to increased resolution when assessing animal model behavior within a particular housing paradigm.
Image Credit: Noldus
PhenoTyper can be customized to suit individual research needs. Each configuration is comprised of a bottom plate, four interchangeable walls, and a PhenoTyper top unit. A variety of walls are available to accommodate any configuration, with attachments for accessories such as feeding stations, drinking bottles and shelters.
The PhenoTyper top unit houses LEDs and a camera for automated tracking, with other sensor and stimuli options available. These can also be used to transmit feedback on animal behavior to EthoVision XT.
Automated tracking using EthoVision XT can provide full data integration and allow automation of experiments. EthoVision XT also offers precision tracking and good calculation of an extensive range of physiological and behavioral parameters while offering researchers access to unrivaled versatility in data processing and visualization.
As a result, EthoVision XT is considered to be the most cited video tracking system in the world.14
Image Credit: Noldus
To discover how PhenoTyper can offer deeper insight and faster results, contact Noldus today.
References
- Russell, W. M. S. & Burch, R. L. (1959). The principles of humane experimental technique. The principles of humane experimental technique
- Poole, T. Happy animals make good science. (1997). Lab Anim 31, 116–124
- Baumans, V. (2005). Science-based assessment of animal welfare: laboratory animals. Revue Scientifique Et Technique-Office International Des Epizooties 24, 503
- Code of Practice for the Housing and Care of Laboratory Mice, Rats, Guinea Pigs and Rabbits | Agriculture Victoria. https://agriculture.vic.gov.au/home
- Kappel, S., Hawkins, P. & Mendl, M. T. (2017). To Group or Not to Group? Good Practice for Housing Male Laboratory Mice. Animals (Basel) 7, E88
- Hohlbaum, K. et al. (2020). Social enrichment by separated pair housing of male C57BL/6JRj mice. Sci Rep 10, 11165
- Schipper, L., van Heijningen, S., Karapetsas, G., van der Beek, E. M. & van Dijk, G. (2020). Individual housing of male C57BL/6J mice after weaning impairs growth and predisposes for obesity. PLoS ONE 15, e0225488
- Schipper, L., Harvey, L., van der Beek, E. M. & van Dijk, G. (2018). Home alone: A systematic review and meta-analysis on the effects of individual housing on body weight, food intake and visceral fat mass in rodents. Obesity Reviews 19, 614–637
- Liu, N. et al. (2019). Single housing‐induced effects in cognitive impairment and depression‐like behavior in male and female mice involve neuroplasticity related signaling. European Journal of Neuroscience 52,
- Pasquarelli, N., Voehringer, P., Henke, J. & Ferger, B. (2017). Effect of a change in housing conditions on body weight, behavior and brain neurotransmitters in male C57BL/6J mice. Behavioural Brain Research 333, 35–42
- Buckinx, A. et al. (2021). Exploring Refinement Strategies for Single Housing of Male C57BL/6JRj Mice: Effect of Cage Divider on Stress-Related Behavior and Hypothalamic-Pituitary-Adrenal-Axis Activity. Frontiers in Behavioral Neuroscience 15
- Xavier, A. L. R. et al. Cannula Implantation into the Cisterna Magna of Rodents. J Vis Exp 57378 (2018) doi:10.3791/57378.
- Home cage & Welfare - PhenoTyper. Home cage & Welfare - PhenoTyper https://www.noldus.com/applications/home-cage-welfare.
- Benefits - EthoVision XT. Benefits - EthoVision XT https://www.noldus.com/ethovision-xt/benefits.
About Noldus Information Technology
Noldus Information Technology was established in 1989 by Lucas Noldus, founder and CEO of the company. With a Ph.D. in animal behavior from Wageningen University, he developed the company’s first software tool during his research in entomology. Noldus has strived to advance behavioral research ever since, evolving into a company that provides integrated systems including software, hardware, and services.
We now offer a wide range of solutions for research in animal and human domains, including biology, psychology, marketing, human factors, and healthcare. We work with leading suppliers and develop innovative, state-of-the art products. We also offer excellent technical support and customer care. As a result, our systems have found their way into more than 10,200 universities, research institutes, and companies in almost 100 countries.
The success of our company is determined to a large extent by the enthusiasm and creativity of our employees. We encourage each other to think outside the box, which leads to unique products and services for our customers. And we are always on the lookout for new talent!
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