Animal Husbandry, Environmental Enrichment and Occupational Health and Safety

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Chapter 5

Animal Husbandry, Environmental Enrichment and Occupational Health and Safety

Animal Husbandry

Experimental animals are a part of the experimental system, so it is important to minimise variation between animals in a study (see Chapter 6). Animals that give reproducible results in experiments should therefore be raised under standard conditions which keep the animals free of unwanted disease and stress and maintain their defined microbiological status. Any recommendation affecting the health or husbandry of the animals must therefore be considered together with the science that is being carried out. Housing animals in a good-quality environment will result in better experimental models in a range of different areas of research and testing. In toxicology, the old belief that the best way to standardise results is to house animals in barren conditions has been repeatedly challenged in the scientific literature, which shows that stress and anxiety due to inappropriate husbandry will affect animals, and therefore data, in unpredictable ways. Just as most scientists will accept and use models that have been improved by using new equipment, techniques, reagents or strains, they should also accept and use models that have been improved by refining husbandry: the principle is exactly the same1.

Laboratory animals do not have the freedom to move away from adverse conditions, to search for food and water or to find a better nesting site. All their physiological and behavioural needs must be supplied by the laboratory environment. These needs are not optional: they must be catered for or poor health will result. Following the application of the five freedoms2 – which are reiterated in the UK Animal Welfare Act 2006, which protects all laboratory animals, in addition to the Animals (Scientific Procedures) Act 1986 – the freedom from hunger and thirst means there must be optimum diet supplied to ensure growth, reproduction and longevity and free access to food and water. Freedom from discomfort means there must be adequate shelter and warmth, and a comfortable resting area. Freedom from pain, injury and disease means that disease and injury must be prevented and treated where necessary. Freedom from fear and distress means the conditions must avoid mental suffering; and freedom to express normal behaviour means there must be adequate space to allow a normal range of movement, without overcrowding, and social company.

Guidelines on the care of laboratory animals are published in Appendix A to the ‘Convention on the protection of vertebrate animals in experimental and other scientific procedures’3. For those in the USA or in institutes working to the Association for the Assessment and Accreditation of Laboratory Animal Care International (AAALAC) standards, the National Research Council Guide for the Care and Use of Laboratory Animals is the accepted text4. These documents give details of recommended environmental conditions, and include minimum cage sizes and stocking densities.

In addition to considering food, bedding and water provision, and the type of caging in which the animal will be kept, the training and experience of staff, handling methods and the overall environment, such as the level of background noise, can all have an effect on the animal, which may be manifested in some way that affects the study being carried out.

Types of housing

The microbiological status of an animal will depend on the level of control that is exercised over its exposure to different organisms. Housing for laboratory rodents, rabbits and some larger species is now usually designed in such a way as to offer a barrier for microbiological containment. This may be done because it is required as a strategy for the containment of animals which may pose a risk to human safety, because they are carrying biological agents that fall into hazard groups categorised by the Advisory Committee on Dangerous Pathogens. Sometimes the principal requirement is to protect staff from animal allergens, or it may be to prevent the microbiological spread of organisms between animals in order to maintain their health status, perhaps to allow animals of different microbiological backgrounds to be housed in close proximity. There are various terms used to describe the microbiological status of laboratory animals (e.g. conventional, or specific-pathogen-free (SPF); see the section on Sources of infection in Chapter 6), which in turn indicates the type of housing in which they are kept in order to ensure adequate biosecurity to maintain that level of microbiological status. The biosecurity barrier can be at the level of the cage/pen type and also at the level of the type of facility. Cages must be made from harmless material which is easily cleaned and sterilised, and must be able to withstand attempts to escape. The following descriptions are in increasing order of biosecurity.


In conventional housing animals are housed in cages or enclosures which are open to the atmosphere of the room or building. For rodents, polycarbonate shoebox cages with a wire lid on open shelving or racks are relatively inexpensive, durable and easy to clean, but provide no barrier to microorganisms and therefore animals are at risk of exposure to infectious agents. Larger animals are often held in conventional facilities.

Filter-top cages

Cages are held on an open rack, but covered with individual filters above a conventional wire lid. Some containment of microorganisms is achieved with well-fitting lids, but the microenvironment in the cage is compromised as there is restricted airflow. The barrier remains at cage level and relies on an air-tight seal and passive movement of air through the filter. The filter top should only be removed in a cage-changing station/safety cabinet, which can make them difficult to work with.

Ventilated cabinets

These are similar to sealed cupboards with their own filtered air supply. The cabinet operates under negative pressure. Inside, filter-top cages are generally used. They are easy to install, relatively cheap and mobile but can present a risk when the cabinet doors are open or at cage changes.

Individually ventilated caging systems

Increasing use is being made of individually ventilated cages (IVCs) for laboratory rodents, to keep the animals at a defined health status. These cages are usually of the shoebox type, made of polycarbonate plastic, but they have filter tops held in a specialised rack that allows each cage to receive its air supply individually. Air is forced into or drawn out of the cage through nozzles adjacent to the lid. Cages can be held at positive or negative pressure, depending on the nature of the barrier to either reduce risk of pathogen contamination or to provide containment. The pressure is variable and is determined by whether or not the cage is sealed. Air movement through the nozzles produces sound, but in general the lower the air speed the lower the noise level is likely to be. The background noise and vibration in such units has been found to have an effect on some strains of mice5. The fans and filters used may be connected directly to the cage rack within the animal room, or may be sited remotely within a service plant room. If fans are situated on the cage rack, vibration may be transmitted to the cage. Whatever the design, it is crucial to install an alarm system, and to consider procedures in the event of a breakdown or power failure.

The containment provided by the cage system must be maintained while the cage is cleaned or the animals examined. These procedures are therefore carried out in ventilated workstations or safety cabinets. There are three classes: class I protects the operator, class II protects the animal and the operator and has an easy-access open front and class III is, in effect, a totally sealed box. IVCs are complex cage systems that rely on engineering to support the animals’ environment. If this equipment is to fulfil its objectives thorough staff training is required, ranging from simple husbandry procedures to prevent damage to cages, to knowing how to ventilate a rack of cages when a fan unit breaks down since such failures can lead to risk of suffocation. Standard operating procedures are required for IVCs and safety cabinets to ensure that the required level of containment is maintained.

The use of IVCs is increasing as they provide protection of valuable transgenic lines of mice from environmental pathogens, and can increase room capacity. The cages also require less frequent changing. The system allows for containment of animals that are in quarantine or are infected, and are easier to work with than isolators. They also provide protection of staff from allergens. The IVC provides the animal with an environment that is controlled for ventilation, temperature and relative humidity. The containment provided by an IVC may be beneficial: the quality of the science may be improved by using healthier animals, enabling fewer animals to be used more effectively. There are drawbacks, however, since this type of caging makes the animal more remote from the staff. The animal technician cannot see the animal as easily, and cannot hear or smell the animal, all valuable sources of information when assessing its overall condition. The welfare of the animals will depend on the qualities and skills of the staff employed. Their success relies on ‘operating procedures’: and there is a risk of cross contamination, for example, at cage servicing6.

Flexible film isolators

These are used mainly for small rodents but sometimes also for gnotobiotic or germ-free large animals (pigs, poultry, calves). An isolator is like a large plastic bubble, which is sealed from the outside world. Filtered air is supplied, and equipment and food are passed in through a port which allows disinfection of the packaging prior to entry into the isolator. Isolators operate under negative or positive pressure, offering complete environmental protection against the spread of pathogens into or out of the isolator, so animals of different health status can be housed in the same room, in different isolators. They can be used for containment of animals with zoonotic pathogens; for example, Advisory Committee on Dangerous Pathogens category 3, protection of valuable or immunodeficient animals and for quarantine of animals from various sources. They are mobile but do not make good use of available floor space. They must be alarmed in case of failure of the air supply and they can be difficult to work with.

Bedding and nesting materials

Bedding material needs to fulfill a number of requirements. It must provide warmth and be comfortable for resting, and must absorb urine. It should be non-toxic, not dehydrating for neonates and relatively dust-free.

Many animal species need to be in control of their microenvironment. They huddle and build nests in order to adjust the temperature, humidity and light, all of which will impact on the animal’s physiological and psychological status. Cages or pens should therefore have a solid floor with bedding for digging, nesting and resting, and the animal should be able to create separate spaces for sleeping, defecating, urinating, eating and playing. What is important about a cage or pen is not its size but its complexity. Sawdust is a popular choice for bedding material, but fine particles can cause preputial and respiratory problems. Nest boxes may be provided, but animals may need additional nesting material. Paper towels, tissues and wood wool allow the animal to regulate microclimates, create a shelter to hide and control the social environment. Use of used nesting material, rather than bedding material, can reduce aggression. Softwoods such as pine should be avoided as they contain hydrocarbons that may induce hepatic microsomal enzymes7.



Any laboratory animal must be fed an adequate diet that is nutritionally complete in an appropriate quantity. Overfeeding will lead to obesity which is associated with an increased incidence of tumour development, whereas calorie restriction has been shown to increase longevity. Even when on maintenance diets, rodents show a tendency towards obesity8. High-protein diets have been associated with renal failure. Consistent composition and quality of the diet are essential to reduce experimental variability. The food must be palatable, which will depend not only on flavour (low-fat food is less palatable) but also on its physical form, such as the hardness and size of the pellets. The composition of diet can affect the experimental outcome. In toxicity testing the diet may bind toxins, and may alter gut microflora and drug metabolism. The toxins given to the animals can also affect the diet by degrading constituents, suppressing appetite and/or reducing palatability. Other points to note about diet are that the heat treatment used in production of extruded or expanded pellets will destroy most bacteria. If further sterilisation is required it can be done by irradiation or autoclaving. Diets have a limited shelf life and must be stored correctly to ensure they do not deteriorate.

Water supply

Bacterial contamination can be controlled by acidification or chlorination. Trace elements, heavy metals and organic chemicals can be removed by reverse osmosis, de-ionisation or microfiltration. Automatic watering systems may appear to save time and ensure a constant water supply, but in solid-floored systems care must be taken to prevent flooding. Water pressure must be monitored continuously to ensure that the flow is adequate. It is necessary to avoid both flooding and dehydration and to clean the central reservoir regularly and check for contamination with bacteria and fungi. All watering systems need to be checked and cleaned frequently.


The Home Office Codes of Practice9,10, which will be updated during 2013–2014, and EU Directive 2010/63, Annex III, set out minimum standards. The macroenvironment is the set of conditions outside the cage which can impact on the animals, and the microenvironment is the set of conditions within the cage, which may be very different to those outside. It is important not to ignore the microenvironment which is critical for the animal, sometimes there is a tendency to just concentrate on and monitor the macroenvironment.

Temperature and relative humidity

The most important of environmental factors is temperature. Animals will respond to changes in temperature by altering their metabolic rate so changes in ambient temperature can affect experimental results by altering drug activity, toxicity and metabolism; feed and water intake; susceptibility to disease; and reproductive performance and growth. All of these may affect experimental data being collected. Factors which affect the temperature in the microenvironment include the cage type (metal/plastic), whether or not it has a filter top, the presence or absence of bedding or nesting material, the housing density in the room (as more animals generate more heat) and the presence in the room of other equipment that may generate heat. Temperature regulation is also affected by relative humidity which can be difficult to control, especially in winter. The specified level is 55±10%. Humidity outside this range will predispose to disease: respiratory disease in rats or nasal dermatitis in gerbils can occur if humidity is high, or ringtail may arise in rodents if it is low. Temperature and humidity should therefore be regulated to keep within the prescribed limits. Most modern animal units have a Building Management System to record temperature, provide supplementary heating or cooling and regulate ventilation, which will influence temperature, humidity and gaseous and particulate contaminants aiming to reduce the level of smells, dust, gases (e.g. ammonia), infectious agents and allergens. Inadequate ventilation leads to rises in ammonia, carbon dioxide and humidity plus dust if poor-quality bedding is used. Ventilation rates should be related to stocking density and heat generated by equipment in the animal rooms, and can be used to create differential pressures. A minimum of 15–20 air changes per hour is recommended for rodents, but achieving these rates at the room level does not guarantee adequate changes at cage level and does not necessarily ensure an adequate microenvironment.


Excessive background noise or intermittent loud noise should be avoided as it can cause poor reproductive performance, audiogenic seizures (in gerbils, DBA2 mice or Lister hooded rats) and an abnormal response in studies involving stress. Rodents can hear high-frequency ultrasound not audible to humans, such as that emitted by computers (20–30 kHz).


Lighting can have a major influence on an animal’s physiological and behavioural responses in two ways, as follows.

1. Photoperiod: the light/dark cycle regulates the circadian rhythm and reproductive cycles. A 24 h cycle of 12 h:12 h or 14 h:10 h is normal for rodents. Changes in proportion will affect gestation period, oestrus cycle and time of ovulation. Interruptions during the dark cycle are particularly disruptive of circadian rhythms and oestrus cycles and can lead to enhancement of tumour growth.

2. Intensity: ‘normal’ office light levels are 300–400 lux but light intensities above 60 lux can lead to retinal degeneration in albino animals. Cages on the top of a rack may be exposed to much higher levels of light than those below and should always be provided with a shelf over the top. Aim for an intensity of 200 lux 1 m from the floor and intensity of 25 lux at cage level by providing boxes, tubes or igloos for sleeping, tinted cages and turning down lights when not working in the room.

Animal rooms generally do not have windows since their presence will lead to variation in light intensity, photoperiod and temperature, and possible lapses in security11.

Handling techniques

Good animal handling techniques will reduce the risk of injury from bites and scratches and will increase the confidence of both the handler and the animal, thus reducing stress to all involved. All animals will respond in some way to the presence of a human and most species can recognise individuals and will be nervous of strangers. It is therefore important for the researcher to establish a friendly relationship with the animal to reduce nervousness on both sides. An animal that is confident and relaxed with its handler will be more co-operative, enabling procedures to be carried out more easily. Some aspects of handling will vary according to the species.

Environmental Enrichment

Animals in the wild will find and process food, build nests, defend their territory and socialise, whereas animals in captivity in the laboratory have little opportunity to pursue such behaviours. This potentially results in adverse effects on their welfare and physiology. It is therefore necessary to make alterations to the environment which enhance welfare and increase the frequency and diversity of natural behaviours. For all species the enrichment strategy should permit socialisation, preferably direct but at least visual, the accommodation should provide an interesting, stimulating environment, there should be variation in textures and taste in feeding and foraging, and the animal should have access to some manipulative objects. In order to be classed as an ‘enrichment’ it must increase the frequency and diversity of positive natural behaviour, decrease frequency of abnormal behaviour, maximise utilisation of the environment and increase an animal’s ability to cope with the challenges of captivity.

However, the provision of environmental enrichment can cause controversy, because even though an enriched environment may produce more ‘normal’ animals and enhance their welfare, it may also change their biological characteristics and may increase variability. It must therefore be compatible with the study. In general, captive domesticated rodents need:

  • properly structured space,
  • solid floors with litter,
  • group housing for social animals,
  • refuges,
  • nesting material,
  • treats for foraging,
  • positive (or less negative) interactions with humans,
  • an appropriate duration and intensity of light and dark.

The provision of environmental enrichment for animals held in the laboratory is now accepted as standard practice. However, it is important to ensure that any enrichment provided is actually beneficial to the animals, rather than just a token gesture. One must therefore evaluate the enrichment and know what the animals wants and what it needs, and to satisfy those desires as much as possible. Many people have spent a great deal of time and effort on developing environmental enrichment for laboratory animals and refining other aspects of animal housing and care, only to find that their improvements are not implemented because they are not considered ‘scientifically validated’ or are unacceptable for other reasons. This problem can be overcome by a structured, scientifically robust approach to evaluating enrichment and other husbandry refinements. Providing a good-quality ‘home’ environment is an essential component of ensuring good laboratory animal welfare. A suitable environment will allow the animals to perform a range of natural behaviours including social behaviours, and different sorts of locomotion, exploration, hiding and foraging. It can also distract them from any pain, discomfort or distress they may experience and improve the ability to monitor them since, if animals can display a broad range of behaviours, it is easier to recognise changes that could indicate suffering. Inappropriate animal husbandry can lead to physiological and psychological stress and this may reduce the quality of the science12.

Refinement of animal housing and care is as important for good animal welfare as it is for good science, but there are some conflicting demands and mixed messages that can make implementing this difficult. For example, there may be different interpretations of animals’ behaviour, what they need and how this can be safely provided, and a lack of awareness about refinements that have already been validated and are successfully used. People may have concerns that cages could become cluttered with items that animals do not really need, wasting time and money and making it difficult to check the animals and keep the cages clean. There may be an unwillingness to risk any disruption to standardised research methods or to change established or traditional practices without proof that animals will benefit and that data quality will not be compromised, particularly if there will be difficulty in obtaining the necessary financial and human resources. In order to reconcile these issues there should be objective evaluation of what is best for the animals.

Evaluation of enrichment and other refinements to housing and care

There are three important considerations when evaluating a husbandry refinement: the potential impact on:

1. the animals: whether it is relevant to the needs of the species and strain; whether it could genuinely improve welfare and encourage a range of desirable behaviours; or whether it could cause undesirable harms, behaviours or mental states, such as toxic reactions, aggression or anxiety;

2. the science: whether it could have a significant impact on scientific validity;

3. the management of the animal facility: whether it would require changes to animal house management and resource allocation.

Dissemination of the results is also important. Feedback and communication are important, whether or not the enrichment was a success. Enrichment should be discussed in research establishments, such as in ethical or animal care and use committees, species user groups or scientific user committees and external meetings.

Evaluating the effect of a potential refinement on animals

When considering how to improve standard laboratory animal housing it is important to think in terms of the senses and behaviour of the animal species (and strain) that the housing will accommodate. For example, mice and rats are nocturnal ‘prey’ species that live in an olfactory and tactile world; they can communicate in ultrasound, are sensitive to ultraviolet light, live in social groups and have large home ranges. Unsupplemented and unmodified commercial laboratory rodent housing does little to meet the animals’ needs, although it does meet human requirements for uniformity, hygiene, disease control, economic viability and efficient use of space.

It is highly desirable to reduce the conflict between the needs of humans and animals by defining housing that will better fit the animals’ requirements. A good foundation for this is reviewing the literature on the natural behaviour of the species and the environment that it evolved to inhabit. Animal welfare science research techniques can then be used to evaluate whether animals benefit from particular refinements and, if they do, how much they want them.

Sometimes it is argued that years of domestication and inbreeding have changed laboratory rodents, especially rats and mice, so that they no longer need many of the environmental features that are important to animals in the wild. This is not the case; rodents undoubtedly can adapt to their living conditions, as can any species, but this does not mean that the similarities between rodents in the laboratory and their wild counterparts should be ignored. Many studies where laboratory mice and rats (even of highly inbred strains) and cage- farmed rabbits have been released into large, outdoor enclosures have shown that complex, natural behaviours are innate, even after many generations of domestication. Social behaviours, dominance hierarchies, tunnel- and nest-building behaviour and anti-predator behaviours are all rapidly expressed (see Standard mouse caging represents under 3% of the 2 m2 range observed in some wild mice. A standard size guinea pig cage is just 0.03% of the wild animal’s 1500 m2 range.

Asking animals what they want

Animal welfare science is a very broad discipline that studies animal physiology and behaviour at a variety of levels, from measuring the level of ‘stress’ hormones in the blood, through to studies of the behaviour of whole animals and the way that they interact with other animals and the environment. There are three broad areas of study that are often used when evaluating refinements: monitoring behaviour, choice or preference tests and motivation tests.

Monitoring behaviour

Animal behaviour is relatively easy to observe and monitor, but it is difficult to interpret and define which behaviours are desirable in a captive situation. Animals should be free to display a range of natural behaviours, appropriate for their species, but of course not all ‘natural’ behaviours are enjoyable (such as fleeing from a predator). Before monitoring behaviour it is essential to be able to define which behaviours are ‘normal’ and ‘desirable’. In practice, the aim is generally for animals to display a wide range of behaviours as appropriate for the species, but advice should be sought on defining and interpreting animal behaviours, because it may not always be straightforward which are desirable in a captive situation. Distinctly abnormal behaviours are easier to identify. For example, it is known that a stereotypic behaviour indicates that an animal is (or has been) struggling to cope with an inappropriate environment. The behaviour may be ‘normal’ in a given situation, but is not desirable. The goal with laboratory animal housing should be to protect animals while allowing them to carry out appropriate occupations such as exercise, foraging, nesting and social interactions including play.

Animal behaviour should be recognised and monitored as objectively as possible. One common method is to set out an ethogram, which is a list of behaviours that may be carried out by an animal, and use this to calculate a time budget, which lists the percentage of time that an animal spends on different activities. Ethograms and time budgets can be used to assess animal behaviour before and after an enrichment item is added, for example, to see whether and how the item is being used. A good protocol for monitoring animal behaviour in response to refinement will also include behaviours that indicate positive welfare, which could include a good level of social interaction with cage mates, play and positive interactions with human handlers. A Wiki Ethogram for the laboratory mouse is available online at (note US spelling).

Animals may only perform some behaviours for a brief period of time, yet the ability to do so may be very important to them. For example, certain cage features might be important during aggressive encounters, or group-housed animals may spend only short periods grooming one another. When setting an appropriate time period for use it is important to think about how the enrichment or resource is used and any suffering that might result if it were not available, even if the animal only interacts with it for a short time.

Choice or preference tests

These tests offer animals a simple choice between two or more different environments. They are based on the fact that animals generally choose in their own best interests, except in highly artificial or confusing circumstances, so there is a close connection between the conditions animals prefer and those in which their needs are met and their welfare is good. Preference tests may provide a choice between (1) a standard cage and one containing an enrichment item, (2) two types of enrichment or (3) any two environments that provide different conditions such as temperatures or light intensities. Animal preference is an important way of assessing enrichment, as the animals’ choices indicates what they really ‘want’. However, animals may not make good choices between artificial options, so they may make choices that are not in their long-term interests. The preference test must be designed so that the animal is familiar with all of the options and knows how to select them. Care must be taken to design preference tests correctly, and not to allow factors such as novelty or time of day to act as confounding variables. Preference tests can show which of the available items, or conditions, an animal prefers. This may provide sufficient information to make a decision; for example, on which kind of nesting material to buy or how to set light levels. However, these tests do not indicate how important it is to the animal to have the preferred option. This can be assessed by carrying out a test of motivation.

Motivation tests

Motivation tests involve animals choosing to ‘pay a price’ to gain access to something they want, such as more space, a nest box or their cage mates. The ‘price’ can be lifting a weighted door, squeezing through a gap or having to make the effort to climb up a slope. The slope is increased with each trial, and the point at which the animal will no longer make the effort to climb it represents the cut-off point for the price it is prepared to pay. This type of study has allowed researchers to gain considerable insights into what animals really want and need, and how the importance they attach to features of their environment can vary at different developmental stages, times of day, seasons and stages in their reproductive cycles.

Practicalities for evaluating whether enrichment works

Before any enrichment is provided, expert advice should be sought on the natural behaviour of the animal, and then evaluation studies carried out to make sure the enrichment is having the desired effect. Before evaluation studies are conducted it is essential to seek advice on experimental design and analysis. Depending on the type of study it may need to be discussed with the regulator and others who could be affected, such as the care staff and researchers who will be implementing the refinement and working with the animals involved, respectively.

When deciding on a husbandry refinement and how to evaluate it, preliminary considerations include:

  • current housing, husbandry and care, and any areas where refinement is required, for example whether animals are singly housed or the environment is barren,
  • what the best type of refinement might be to address any outstanding needs,
  • if an enrichment item is proposed, whether it is safe and suitable,
  • who the evaluation study might need to be discussed with, in-house and/or externally,
  • how much time would be available for the study and when staff would be free to conduct it.

Enrichments and resources may be divided into two categories – (1) enrichment items and resources and (2) environmental conditions and husbandry refinements – due to the different approaches to evaluating each. In the case of enrichment items, monitor how an animal’s behaviour changes, quantify the level of interaction with the item and see how the animal uses it. With environmental conditions and husbandry refinements, evaluate how behaviour changes and, in some cases, whether the animal chooses (or is prepared to work for) a particular environment.

There are some important points to consider in relation to animals’ potential responses to discrete enrichment items such as chew blocks. For example, patience may be required if animals are neophobic (e.g. rodents); individuals should be able to retreat from new items if they are feeling anxious and be allowed time to habituate if necessary. If there is a risk of competition for new items, these should be supplied so that each individual has easy access (e.g. refuges) or there is at least one each (for smaller items). As well as thoughtful experimental design, these issues can be addressed by ensuring that everyone responsible for monitoring the animals is familiar with any signs of harm or distress that might occur, and is aware of end points at which the study should be stopped.

For a scientifically valid assessment of the impact of a refinement there has to be a control condition, which is not subjected to the experimental manipulation but is the same (or as similar as possible) in all other respects. Only one factor should be varied at a time, otherwise it is not possible to tell which has made a difference. In the case of studies to evaluate refinement, the control condition should be animals housed and cared for according to the normal husbandry protocols at the establishment, not animals in a barren enclosure. For example, if rats are normally group-housed with nesting material and chew blocks and the study aims to evaluate the effect of a refuge, then the control condition is groups of normal size and composition, nesting material and chew blocks and the experimental condition is the same but with the refuge added. A potential confounding variable that should not be overlooked is extra human attention, as colleagues may be interested in refinement evaluation studies, but can inadvertently ruin them by going to look at the animals more frequently than would normally be the case.

Data should also be collected so that the right kind of statistical analysis can be applied, which means using the right number of animals, making the right number of observations and using the right statistical tests. It is a good idea to consult a statistician when designing studies – rather than finishing the study and then asking for advice – as it may be the case that the data cannot be analysed and the whole study would have been pointless.

If the trial indicates that the refinement would benefit the animals, the next stage is clearly to consider how to implement it. It is important to introduce the new items at appropriate times and to monitor animals carefully in the short and long term. If an enrichment item is not used appropriately or as envisaged then its use should be carefully reviewed and consideration given to altering it or trying something different. Different strains can have highly specific needs and preferences, and it can take time to devise the most appropriate husbandry protocol for each one.

Evaluating the effect of a potential refinement on science

Once it has been demonstrated that a refinement will benefit animals and not cause them harm, the next step may be to address any questions about its impact on scientific validity or data quality. For example, there may be concerns that refinement will introduce another variable, which might reduce data quality; that more animals might be required due to increased variability; or that the data may not be comparable with previous data obtained from animals kept in standard housing13.

All of these concerns need to be explored, to see whether they will occur in practice and whether this would actually be a problem. It should never be assumed that any refinement will adversely affect scientific results without objectively evaluating the impact, for example via literature searches or pilot studies, in which a small number of animals on the scientific study in question are provided with the husbandry refinement and the data analysed to see whether it has been affected. The use of pilot studies may raise concerns about using additional animals in regulated procedures, but it may still be possible to use the data in the main study, in which case there are no additional harms. Even if the data are not suitable, it may be appropriate to implement the refinement, while quantifying and allowing for its effects, as there will be a longer-term benefit for animals if the welfare of individuals in subsequent studies is improved. There will also likely be a scientific benefit, as different data from animals in suboptimal housing may well be flawed.

Concerns are sometimes expressed that accommodating the effects of husbandry refinements on scientific data may necessitate using more animals, which is obviously counter to the principle of Reduction. However, this needs to be assessed on a case-by-case basis, as there are many instances where it is preferable to use more animals, provided that each one suffers less and has a better quality of life. It is very important to give priority to the experience of individual animals when balancing the need to reduce numbers against the need to reduce suffering. The local animal welfare and ethical review body can play a role in considering the harms and benefits of different approaches and resolving any conflict between the desires to reduce and refine animal use.

It is extremely important to promote dialogue and greater awareness of the implementation (and benefits of evaluation) of husbandry refinements, as this can help to allay any concerns about their impact on the science and also help in the interpretation of scientific publications. Adequate detail of husbandry protocols should be included in papers, posters and talks; for example, the Animal Research: Reporting In Vivo Experiments (ARRIVE) guidelines outline what is necessary and how this can be achieved (

Evaluating the effect of a potential refinement on animal house management

After establishing that animals will benefit from enrichment and the science will not be adversely affected (or may even benefit), the altered husbandry protocol will need to be resourced, with respect to funding and time, and introduced on a wider scale. Different establishments will have different processes in place for this in enrichment evaluation, but all should involve (1) risk assessment and (2) evaluating the practical and financial issues associated with the changes in husbandry.

The assessment should aim to predict, as far as possible, any risks to:

  • animals: this will include risks such as injury or aggression, to ensure that these can be minimised,
  • humans: such as problems with ergonomics, manual handling issues or potential for disorders such as repetitive strain injury (RSI);
  • equipment: for example, whether cages or cage washers could be damaged.

The process should involve defining clear action points so that all relevant personnel know when and how to respond if any hazards occur to the animals, staff or equipment once the refinement is implemented. There should also be an effective system for recording problems in any of the three areas and reporting these to the relevant individual(s) or body.

It will also be necessary to quantify how much it will add to working time to implement the refinement; for example, regarding cage or pen cleaning and monitoring animals (during the initial implementation of the refinement and in the longer term). Additional staff resource may be necessary to accommodate the refinement, which should be offset against the animal welfare and scientific benefits that are likely to be realised. Where the husbandry refinement is in the form of an item such as a refuge, additional factors to be considered include its provenance and cost; whether it can be reused (and if so how it is cleaned and how long it will last); and whether there is a long-term supply of the item, as it would be highly undesirable to have to change it part-way through a long-term study. A pilot study may be necessary if it proves to be difficult to predict the various risks and other practical issues. Conducting this during acclimatisation or habituation periods could help to allay concerns relating to study delays.

There should be regular discussion and exchange of ideas and review involving animal care staff, veterinarians, scientists and the animal welfare and ethical review body; each individual approach will depend on a variety of factors including the nature and purpose of the studies, the size of the establishment and its organisational systems.

Supply and Transport

One aim of the EU Directive 2010/63 is to guarantee the quality of laboratory animals and to provide safeguards, ensuring that, whenever possible, the animals used have been specifically bred for the purpose. The Federation of Laboratory Animal Science Associations (FELASA) code of practice3 requires that regular health monitoring programmes be implemented in breeding establishments, to ensure that laboratory animals remain disease free. Many commercial breeders now exist which can deliver high-quality, high-health laboratory animals. Research animals may come from a wide variety of sources. They may come from the same facility in which the experiments are being carried out, from another animal facility in the same organisation (for example, another animal unit of the same University), from colleagues or collaborators at another research institute working in the same field, from a commercial supplier or even from the wild. Some of these sources may be from another country which may or may not be within the EU.

The transport of animals within the EU is regulated by EC Council Directive 91/628/EEC on the Protection of Animals during Transport15. The import or export of laboratory animals must comply with the relevant international legislation and transport regulations. For animals travelling by air, the International Air Transport Association (IATA) Live Animals Regulations define the responsibilities of shippers and carriers, and container requirements, and are updated annually. The needs for individual species are listed, including those covered by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). These regulations have been adopted as standard by many countries. Arrangements for the transport of animals should ensure that their well-being is not jeopardised, and that they arrive at their destination in good health. Particular attention should be paid to the health and welfare prior to shipment in order to ensure that there are no subclinical infections that could cause clinical disease during or shortly after transport. Containers should be designed to provide comfort and minimise stress to the animals. They must be leak-proof and escape-proof, be able to be disinfected and be such that the animals cannot damage themselves during transport. Sufficient space should be provided such that animals will not feel any discomfort, taking into consideration the conditions which will prevail during transport. Animals to be transported together should be the same age and sex and from the same source. Species should not be mixed in containers, and animals should not be transported in the same vehicle as their natural predators. There must be adequate ventilation within the container. Vents should be placed on opposite sides of the containers and in such a position that they cannot be occluded. The temperature should be within the thermoneutral zone for the animal. Bedding should provide comfort and absorb moisture, insulating the animal against temperature changes and vibrations. Rodents and rabbits need free access to food and water throughout the period of transport. Water should be available, and provided in leak-proof containers, as mash, fruit or vegetables, or as a commercially available ‘solid water’ gel. It is preferable for dedicated vehicles and staff with suitable experience and training to be used for transportation. Vehicles should be insulated and air-conditioned, with a ventilation system that is independent of the main engine. Alarms should warn of failures of the heating and ventilation system. The vehicle needs to be able to be cleaned and disinfected thoroughly, and back-up systems should be available in case the vehicle breaks down. Animals should be examined by a competent person as soon as they arrive, and the transport should be arranged in advance so that animals can be unboxed and placed in fresh ready-prepared cages immediately on arrival. Stress caused by transport may last for up to 5 days and affects physiological processes such as immunity and reproduction.

Aspects of Health, Safety and Security Affecting Animal Care

There are many potential hazards from research; however, the risks can be minimised by implementing simple control measures through good housekeeping. For example, surfaces should be kept clean and clear from obstructions, waste and other materials. Food bags or waste should not be stored in corridors where people may trip and floors should be left dry after cleaning. Using a vacuum when cleaning cages reduces the risk from airborne allergens. There are many potential hazards associated with research protocols, which may be related to the inherent dangerous qualities of the experimental agents, for example chemicals or virulent biological agents, or the complexity and type of the experimental operation, such as the need to create dust, dander or vapours. Having recognised and identified the hazards, it is possible to devise a protocol for minimising exposure. While the employer in the UK has overall responsibility under the UK Health and Safety at Work Act 1974 to ensure the health and safety of personnel, it is nonetheless also the responsibility of individuals to make sure that they conform to the local rules, for their own safety and that of others.

Researchers may find themselves exposed to numerous hazards in the course of their work. These hazards may be from the animals themselves, or equipment, chemicals, electricity, radiation or infectious agents found in the laboratory. The risk to which the researcher is exposed, however, depends upon a combination of the nature of the hazard and how the hazard is contained to reduce or eliminate exposure. For example, a potentially hazardous compound may present only a minimal risk to personnel if handled in a safety cabinet while wearing appropriate protective clothing. The competence and training of personnel and precautions taken to reduce exposure play an important part in controlling risks in the workplace.

In the UK, the Health and Safety at Work Act 1974 imposes a responsibility on the employer to ensure safety at work for all their employees. Employers have to ensure so far as is reasonably practicable, the health, safety and welfare of their employees at work. This responsibility includes a duty to provide a safe working environment and premises, safe systems of work and appropriate training and supervision. Employers should have written rules and procedures covering basic health and safety requirements. Occupational health and safety personnel need a detailed knowledge of legislation in order to be able to translate it into working practices. In many countries, some occupational diseases such as occupational asthma and some zoonoses must be reported to government agencies, and compensation may be awarded to personnel developing such occupational diseases. Employers are required to respond to employee risk factors, and may have to make difficult decisions about suitability for work both before and during employment. If appropriate action to protect employees is not taken, then the enforcement authorities can resort to legal action against the employer. Increasingly, insurance companies are requiring details of potential hazards and risks in the workplace, and evidence of suitable methods of control, before they will issue policies to employers.


Control of Substances Hazardous to Health (COSHH)

COSHH is the UK law that requires employers to control substances that are hazardous to health. Workers’ exposure to hazardous substances can be prevented or reduced by:

  • finding out what the health hazards are,
  • deciding how to prevent harm to health (risk assessment),
  • providing control measures to reduce harm to health,
  • making sure they are used,
  • keeping all control measures in good working order,
  • providing information, instruction and training for employees and others,
  • providing monitoring and health surveillance in appropriate cases,
  • planning for emergencies.

Most laboratories use substances or products that are mixtures of substances, or create substances, which could cause harm to employees, contractors and other people. The COSHH Regulations apply to any substance which is listed in Table 3.2 of part 3 of Annex VI of the CLP Regulations (see and for which an indication of danger specified for the substance is very toxic, toxic, harmful, corrosive or irritant. This includes:

  • any preparation (mixture) that is dangerous for supply,
  • any substance which has a Workplace Exposure Limit (WEL),
  • any biological agents used at work,
  • any dust other than one with a WEL at a concentration in air above 10 mg/m3 averaged over 8 h, or any such respirable dust above 4 mg/m3 over 8 h,
  • any other substance that creates a risk to health because of its properties and the way it is used or is present in the workplace.

The COSHH Regulations define good control practice as follows.

  • Design and operate processes and activities to minimise emission, release and spread of substances hazardous to health.
  • Take into account all relevant routes of exposure (inhalation, skin absorption and ingestion) when developing control measures.
  • Control exposure by measures that are proportionate to the health risk.
  • Choose the most effective and reliable control options which minimise the escape and spread of substances hazardous to health.
  • Where adequate control of exposure cannot be achieved by other means, provide, in combination with other control measures, suitable personal protective equipment.
  • Check and review regularly all elements of control measures for their continuing effectiveness.
  • Inform and train all employees on the hazards and risks from the substances they work with and the use of control measures developed to minimise the risks.
  • Ensure that the introduction of control measures does not increase the overall risk to health and safety (

Classification, Labelling and Packaging (CLP) Regulation

The European Regulation (EC) no. 1272/2008 on classification, labelling and packaging of substances and mixtures – the CLP Regulation – came into force in all EU member states in 2010, replacing previous legislation. The CLP Regulation adopts the Globally Harmonised System (GHS) on the classification and labelling of chemicals and is being phased in through a transitional period which runs until 1 June 2015. The intention of the CLP Regulation is that substances and mixtures that are placed on the market should be classified, labelled and packaged appropriately and in due course that the same classifications and labelling will be used throughout the world with standardised hazard pictograms.

Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH)

REACH is an EU regulation concerning the registration, evaluation, authorisation and restriction of chemicals, placing duties on businesses producing and transporting chemicals. Producers and importers have to ‘register’ a dossier of technical information about each substance they manufacture or import above a certain weight each year. REACH should result in more information being passed down the supply chain to users. For example, safety data sheets will give more information about the exposure scenarios and risk-management measures that should be taken when using a product.

Genetically modified organisms

Work with genetically modified organisms (GMOs) is covered in the UK by the GMO (Contained Use) Regulations 2000. These provide for human health and safety and environmental protection from genetically modified microorganisms (GMMs) in contained use, and additionally the human health and safety from genetically modified plants and animals (GMOs). The key requirement of the GMO (Contained Use) Regulations is to assess the risks of all activities and to make sure that any necessary controls are put in place. The GMO (Contained Use) Regulations provide a framework for making these judgements, and place clear legal obligations on people who work with GMOs. These regulations require risk assessment of all activities involving GMMs and activities involving organisms other than microorganisms. A classification system, with four levels of containment, is based on the risk of the activity independent of the purpose of the activity. In the UK, notification of all premises to the Health and Safety Executive is required before they are used for genetic modification activities for the first time. Activities involving genetically modified animals and plants which are more hazardous to humans than the parental non-modified organism also require notification.

Health and safety in animal facilities

Animal facilities may present specialised hazards, which are unique. Such facilities are often isolated geographically from other areas of the institution, and the work may involve particular hazards not encountered in other parts of an establishment. It is particularly important that the safety policy for these units has been properly worked out and is familiar to all personnel involved. A set of local rules should be available in each unit, which covers both general and specific safety hazards in the area.

The hazards

The major potential hazards to animal handlers can be divided into three groups:

Jul 30, 2017 | Posted by in GENERAL | Comments Off on Animal Husbandry, Environmental Enrichment and Occupational Health and Safety
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