• Attend to the animals’ specific instincts and needs, in collaboration with expert staff.
  • Discuss acclimation, optimal housing conditions and procedures, environmental factors and any experimental limitations on these (e.g. food deprivation, solitary housing).

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.
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.

How long should animals be acclimatised before an experiment?

Although this must be decided on a case-by-case basis, there is some guidance available.

References about nutrition

Further references about housing and husbandry

This page was updated on 16 April 2021

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