12-Housing and husbandry

Housing and husbandry conditions can have large, unforeseen and undesirable influences upon the best planned scientific studies, whereas animals coping well with their surroundings will deliver the most scientifically valid information in an experiment.
What is the difference between acclimation and acclimatisation? 
Sufficient attention must be made to the animals’ instincts and needs from birth to death. Since most animals are more active in one phase of the 24-hour period, environmental influences may easily be overlooked, particularly if the animals are nocturnal. Issues to be discussed while planning animal studies include:

1. The acclimation period (its anticipated duration, and the criteria for assessing its success).
2. The parameters to be measured during acclimation and the study itself, such as body weight, feed intake, body temperature and behavioural signs.
3. Group or solitary housing of both sexes, stocking densities, the effects of removal of animals from a group, the effects of pain and distress on co-habitants, and environmental effects caused unwittingly by conditions in the holding area (e.g. tank, cage, pen or pasture), including the position of cages/tanks in a room.
4. The size and shape of the housing, including provisions for social and environmental enrichment. Any lowering of minimum standards (e.g. those described in Annex III of the EU Directive 2010/63) must be described and justified, along with the likely effects on the animals and measures to mitigate these.
5. The possible negative welfare effects on the animals of the housing conditions, among other things by preventing natural behaviour, which may lead to contingent suffering (called contingent inhumanity by the authors of the 3R tenet, Russell and Burch). This has the potential to cause as much, if not more, suffering than the experimental procedures themselves, as well as the capacity to confound the science. Norecopa has collected anecdotal advice on experiences with group housing of rodents with cranial implants.
6. Room temperature, relative humidity, water temperature in the case of aquatic species, and acceptable limits for these.
7. Photoperiod, light intensity and noise levels. As well as providing suitable lighting during activity periods, species-specific requirements for adequate sleep must also be met. This is particularly important after physiologically stressful procedures, such as surgery. Sudden noises such as fire alarms or rapid movement by personnel to whom the animals are not accustomed may be more stressful than constant low-level background noise. Seasonal breeders may require a period of torpor, which must be taken into account.
8. Bedding, nesting material, hiding places and (for aquatic species) the presence and type of bottom substrate
9. Procedures for cleaning and disinfection, which may be particularly difficult to achieve in breeding colonies
10. The type and composition of feed, as well as any pre-treatment, including the method and frequency of administration. Nutrient reactions with the test substance or procedure may mask or increase a response to the latter.
11. Justification for the necessity and length of food or water deprivation, its likely effects on the animals (which will be related to the time of day when it is planned) and the avoidance of overfeeding.
12. Water quality and quality control. This will be particularly important for aquatic species, where relevant parameters will include:
    • Water source and pre-treatment
    • Turbidity and conductivity
    • Oxygen content
    • pH, ion strength, salinity and nitrogen content
    • Flow and the number of water changes per hour
    • Recirculation methods and treatment

These may be affected by the type of tank or pen and its size, shape, colour, water level, cleaning routines and light sources.

Other environmental factors include the effects of noise, local ventilation rates (e.g. in individually ventilated cages), ultrasound and the presence of personnel (habituation to their activity, noise levels and odour). In some experiments it may be necessary to consider factors whose physiological effects are less certain, such as the earth's magnetism, air pressure, seasonal changes and lunar cycles.

A large number of references to papers describing the effects of housing and husbandry methods are cited in a paper introducing the IMPROVE guidelines for in vivo models of ischaemic stroke.

• Training and habituation techniques for mice and rats
• Support material for the acclimatisation of mice and rats prior to experiments (from the Swedish 3Rs Center)
• NA3RsC resource pages on rodent housing (mice and rats) and hamsters
• NC3Rs guidelines for the housing and husbandry of mice, rats, guinea-pigs, gerbils, hamsters, ferrets, rabbits, cats, non-human primates, and dogs
• The Macaque website (NC3Rs)
• Marmoset: Current topics in Research, Care and Welfare
• Dancer et al. (2022): Housing and Environmental Enrichment of the Domestic Ferret: A Multi-Sector Survey
• Guidelines for housing and management of research animals
• General advice about using farm animals in research
• Guidelines for the care and use of farm animals in research
• Guidelines for the care and use of birds in research
• Guidelines for nutritional research
• Guidelines for fasting (food deprivation) in rodents
• Vasilev et al. (2001): Three Water Restriction Schedules Used in Rodent Behavioral Tasks Transiently Impair Growth and Differentially Evoke a Stress Hormone Response without Causing Dehydration
• Guidelines for the use of non-human primates
• Guidance on the care and housing of fish, including environmental enrichment, and other aquatic species.

References about nutrition

• Literature from Research Diets Inc.
• Radhakrishnan, Cheng & Pellizon (2022): Open Standard Diets Improve Metabolic and Gut Health Compared to Traditional AIN Diets in Mice
• Griffin, Radhakrishnan & Pellizon (2022): Addition of Soluble Fiber in Low-Fat Purified Diets Maintains Cecal and Colonic Morphology, Modulates Bacterial Populations and Predicted Functions, and Improves Glucose Tolerance Compared with Traditional AIN Diets in Male Mice
• Graber (2021): Is it time to revise the AIN-93 rodent diet formulas?
• Radhakrishnan et al. (2021): Considerations when choosing high-fat, high-fructose, and high-cholesterol diets to induce experimental nonalchoholic fatty liver disease in laboratory animal models 
• Long et al. (2021): Shared and distinctive features of the gut microbiome of C57BL/6 mice from different vendors and production sites, and in response to a new vivarium
• Pellizzon MA & Ricci MR (2020): Choice of Laboratory Rodent Diet May Confound Data Interpretation and Reproducibility
• Siersbæk et al. (2020): C57BL/6J substrain differences in response to high-fat diet intervention
• Pellizzon MA & Ricci MR (2018): Effects of Rodent Diet Choice and Fiber Type on Data Interpretation of Gut Microbiome and Metabolic Disease Research
• Pellizzon MA & Ricci MR (2018): The common use of improper control diets in diet-induced metabolic disease research confounds data interpretation: the fiber factor
• Kick B (2020): Want to know what to feed mice?
• The common use of improper control diets in diet-induced metabolic disease research confounds data interpretation: the fiber factor
• Imprecise diet reporting affects metabolic animal research results
• Unsterilized feed as the apparent cause of a mouse parvovirus outbreak
• Must ad libitum mean always available?
• Refinement of the use of food and fluid control as motivational tools for macaques used in behavioural neuroscience research: report of a Working Group of the NC3Rs
• A possible link between food and mood: dietary impact on gut microbiota and behavior in BALB/c mice
• The role of the gut microbiota on animal model reproducibility
• Bacterial species to be considered in quality assurance of mice and rats (Hansen et al., 2019)
• What is really in our drinking water?
• The Jackson Laboratory Handbook on Genetically Standardized Mice
• The Role of Feed in Aquatic Laboratory Animal Nutrition and the Potential Impact on Animal Models and Study Reproducibility (Brenes-Soto et al., 2019)
• The Influence of Feed and Drinking Water on Terrestrial Animal Research and Study Replicability (Kurtz & Feeney, 2020)

Further references about housing and husbandry

• Advice on breeding and colony management
• Efficient management of genetically altered mouse colonies (MRC Harwell/NC3Rs webinar)
• All the Pups We Cannot See: Cannibalism Masks Perinatal Death in Laboratory Mouse Breeding But Infanticide Is Rare (Brajon et al., 2021)
• Gjendal et al. (2018): Does colour matter? Preference of mice for different colours of the house mouse igloo: an observational study 
• Vital Pup - a website presenting research into neonatal mortality in mice
• Nevalainen (2014): Animal husbandry and experimental design
• Nest building as an indicator of illness
• Freymann et al. (2017): Impact of bedding volume on physiological and behavioural parameters in laboratory mice
• Gaskill et al. (2013): Impact of nesting material on mouse body temperature and physiology 
• Advice on housing and husbandry, and on animal care and monitoring, from the NC3Rs
• Guidebook on Mouse and Rat Colony Management (Charles River)
• Hohlbaum et al., (2020): A separated pair-housing system for mice
• Aggression in group-housed laboratory mice: why can't we solve the problem?
• Recommendations on group housing of male mice from the Swedish 3Rs Center 
• Group and Single Housing of Male Mice: Collected Experiences from Research Facilities in Sweden
• Gjendal et al. (2019): Burrowing and nest building activity in mice after exposure to grid floor, isofluorane or ip injections 
• Overview of scientific papers on the effects of relative humidity on health and wellbeing of laboratory mice and rats
• The effect of relative humidity on water intake of C57BL/6J mice housed under conditions of controlled relative humidity at cage level
• Laboratory mouse housing conditions can be improved using common environmental enrichment without compromising data
• Skop et al. (2020): Mouse thermoregulation: Introducing the concept of the thermoneutral point
• Gouveia & Hurst (2019): Improving the practicality of using non-aversive handling methods to reduce background stress and anxiety in laboratory mice
• Kendrick et al. (2020): A novel welfare and scientific approach to conducting dog metabolism studies allowing dogs to be pair housed
• Hawkins & Golledge (2018): The 9 to 5 Rodent − Time for Change? Scientific and welfare implications of circadian and light effects on laboratory mice and rats
• Out Like a Light? The Effects of a Diurnal Husbandry Schedule on Mouse Sleep and Behavior 
• Are vivarium husbandry schedules at odds with mouse sleep patterns?
• Peirson et al. (2018): Light and the laboratory mouse 
• Noise in a laboratory animal facility from the human and mouse perspectives
• Noise and vibration in the vivarium: resources from Turner Scientific
• Making sense of it all: The importance of taking into account the sensory abilities of animals in their housing and management
• Mouse Ethogram (methods, protocols and background information)
• To Group or Not to Group? Good Laboratory Practice for Housing Male Laboratory Mice
• Evaluation of the effects of space allowance on measures of animal welfare in laboratory mice
• The Time-to-Integrate-to-Nest (TINT) test as an Indicator of Wellbeing in Laboratory Mice
• Effects of Nesting Material on Energy Homeostasis in BALB/cAnNCrl, C57BL/6NCrl, and Crl:CD1 (ICR) Mice Housed at 20°C
• Kearton et al. (2019): The effect of virtual fencing stimuli on stress responses and behavior in sheep
• Rat cognition and environmental enrichment
• Vivarium vs Wild: Which is the best setting for animal research?
• Are happy lab animals better science?
• NC3Rs/AstraZeneca Workshops on rat behaviour
• Norway Rat Behavior Reportoire
• Opportunities for improving animal welfare in rodent models of epilepsy and seizures
• Øremerking av smågnagere i forsøksdyrvirksomheter (Norwegian advice on earmarking av small rodents)
• Training techniques for less stressed laboratory rodents
• Tickling rats for better welfare
• Automated Home-Cage Testing as a Tool to Improve Reproducibility of Behavioral Research?
• The Lower Row Monkey Cage: An Overlooked Variable in Biomedical Research
• Progressing the care, husbandry and management of ageing mice used in scientific studies
• Blom et al. (1995): Development and application of a preference test system to evaluate housing conditions for laboratory rats 
• Prior & Holbrook (2021): Promoting social housing during telemetry studies
• Extrinsic Factors Affecting Animals and Research Reproducibility (a theme issue from the ILAR Journal)
• Good Practice for Housing and Care of Rats and for Mice- RSPCA guidance for members of local ethical review processes. Guidance for other species.