Animal-based scientists are required by law to make sure that they keep any pain, suffering or other harm they cause to the animals they use for research, teaching and testing as low as possible. The Three Rs Principle is applied at the planning stages before any direct work with animals begins. Its purpose is to help scientists to minimise the invasiveness, unpleasantness or noxiousness of anything they do to animals.
The Three Rs Principle is a practical guide to scientists. It is designed to ensure that:
animals which might suffer are only used when necessary (Replacement),
that no more and no fewer animals are used than are required to achieve the objectives of the work (Reduction), and
that if any noxiousness is caused during the work, it is kept as low as possible (Refinement).
Replacement means that animals should not be used at all if the same research, teaching or testing aim can be achieved in other ways. The word "animal" refers to those higher order animals that are capable of suffering or feeling pain. So the first question scientists must ask themselves at the planning stage of a study is "Do I need to use higher order animals at all?"
If the answer is "Yes" then Reduction and Refinement must be applied.
Reduction means keeping the number of animals used to the minimum necessary to achieve the research, teaching or testing purposes of the work. This avoids using unnecessarily large numbers of animals. But it is equally important to avoid using too few animals. If not enough animals are used it will not be possible to interpret the results, and the animals used would have been wasted. So the second question scientists must ask is "What is the lowest number of animals needed for this work?"
Refinement refers to keeping any pain, suffering or other harm which may be caused as low as possible for each and every animal used in the work. This means that every aspect of the work must be reviewed carefully and great care taken to minimise any noxious effects on the animals. Thus, the third question scientists must ask is "How can I minimise the noxiousness of every aspect of this work?" It is worth noting that many studies cause very low or no pain, suffering or other harm to the animals involved, while others do indeed have noxious effects.
The invasiveness, severity or noxiousness of any proposed research, teaching or testing procedure must be given very careful consideration during the planning stages of the work, for two reasons.
First, it is necessary to anticipate the extent of pain, suffering, distress or lasting harm that might be caused to the animals by each part of the proposed procedure, in order to work out the best ways to keep any noxiousness as low as possible using refinement strategies.
Second, it is necessary to balance the expected levels of noxiousness against the anticipated benefits of the work in what is called a Harm-Benefit Analysis (link to Balancing Harm and BenefitD). The aim of this is to make sure that any harm is the lowest that is practically feasible and that the benefits are the greatest that can be reasonably achieved. The benefit must outweigh the harm by the greatest feasible margin for the work to proceed. It is the responsibility of both the animal-based scientists who prepare each research, teaching and testing proposal and the Animal Ethics Committee that reviews it to do harm-benefit analyses.
To help with this process various invasiveness, severity or noxiousness scales have been developed world-wide. These help animal-based scientists work out what the negative impact of a proposed procedure is likely to be on the animals. A noxiousness scale devised and used in New Zealand recognises five grades of severity, ranging from no or virtually no noxiousness, to very high noxiousness.
Note that the higher the noxiousness of a procedure, the greater the anticipated benefits must be before it can be approved. For specific examples at each level of noxiousness click on the relevant grade.
No suffering or noxiousness.
Such procedures would not usually require justification in terms of expected indirect or direct benefits to animals, people or both.
Little suffering or noxiousness.
Such procedures would require justification regarding the expected indirect or direct benefits to animals, people or both.
Moderate suffering or noxiousness.
Such procedures would require good justification regarding the expected direct benefits to animals, people or both.
Severe suffering or noxiousness.
Such procedures would require strong justification regarding the expected direct benefits to animals, people or both.
Very severe suffering or noxiousness.
Such procedures would require the most exceptional justification and would be permitted only very rarely.
In New Zealand the vast majority of scientific procedures produce little or no suffering or noxiousness. Nevertheless, a significant percentage of procedures are given noxiousness ratings of "C" or "X" despite careful application of the Three Rs. Such work can only be undertaken if those doing it can provide strong justification for "C" rated procedures and the most exceptional justification for "X" rated procedures (see Balancing Harm and Benefit). A detailed breakdown of these figures is available from the National Animal Ethics Advisory Committee.
Draize Eye Irritancy Test is designed to show whether chemicals, especially those used on the face, hands and other parts of the body, can damage the eyes. As it is used now, it is a very mild test. It involves placing chemicals, which may be irritants to the eyes, on the surface of the eyes of restrained animals, particularly rabbits. Any irritation the chemicals cause is assessed from tears, redness or swelling. The test is very much milder today than it used to be. That is because very low concentrations of chemicals are used and at the first sign of irritation they are washed out of the eye. Despite this, there has been strong pressure from scientists, as well as from animal welfare, animal protection and other groups, to find replacement alternatives for the Draize Test. Although substantial progress has been made in making the Draize Test much milder and in reducing the number of animals used, in some countries there is a legal requirement for the Draize Test to be done on drugs, cosmetics and other chemicals which might come in contact with the eyes. Non-animal alternatives to the Draize Test are being actively researched. As yet no alternatives which are acceptable to safety authorities have been found, but the search is continuing, and some new approaches look promising.
Higher order animals, according to New Zealand law which regulates the scientific uses of animals (Animal Welfare Act 1999), include all mammals (but not human beings), birds, reptiles, fish (bony or cartilaginous), octopus, squid, crab, lobster or crayfish (fresh and salt water). In the context of research, teaching and testing, higher order animals are also considered to include mammalian fetuses during the last half of pregnancy (i.e. an animal’s babies before they are born), the unhatched young of birds or reptiles during the last half of their development in the egg, and marsupial pouch young. This is because it is thought likely that animals in these stages of development might be able to experience pain and suffering. In comparison, lower order animals include some micro-organisms and non-vertebrate animals.
Note that special conditions apply to any research, teaching or testing procedure proposed for Great Apes. These ensure that virtually no invasive procedures can be done on Great Ape in New Zealand.
LD50 Test — the Lethal Dose 50 Test — involves giving animals chemicals in sufficient amounts to kill half (50 per cent) of them. This test, developed in 1927, is now widely regarded as outdated. Although use of the LD50 Test is still required by law in some countries, many countries now accept other methods. Its purpose is to give a measure of how poisonous or toxic chemicals are. However, scientists and animal welfare, animal protection and other groups have been active in trying to find alternatives to the LD50 test. So far three have been found. These are called the Fixed Dose Test, the Up and Down Procedure and the Acute Toxic Class methods. These approaches substantially reduce the number of animals which are needed to find out how poisonous a chemical is, from 60-80 with the LD50 Test at its worst to 6-10. They also substantially reduce the number of animals showing signs of poisoning and how bad those signs are. These tests are examples of Reduction and Refinement, but not Replacement.
Noxiousness scale - details and examples
Grade O
Procedures which do not cause anxiety, fear, pain or distress such as non-invasive observation of animals in unchallenging circumstances.
For instance: field observations of grazing behaviour on farms, or benign handling of tamed and trained animals which are familiar with all personnel and procedures and with the place where the procedures are conducted. Nutrition and growth studies where production is measured in response to benign dietary changes.
No suffering or noxiousness. Procedures usually require no justification.
Grade A
Procedures which cause minor discomfort or low-level anxiety or apprehension for short periods.
For instance: experiments on completely anaesthetised animals which do not regain consciousness; standard methods of euthanasia that rapidly induce unconsciousness (e.g. anaesthetic overdose); taking a blood sample from a superficial vein; injecting a non-toxic substance; skin tests which cause low-level irritation without ulceration; feeding trained animals by a tube passed via the mouth into the stomach; movement of free-range domesticated animals to unfamiliar housing.
Little suffering or noxiousness. Procedures require justification.
Grade B
Procedures which cause moderate anxiety, fear, pain, or distress for short periods or minor discomfort or distress for long periods.
For instance: recovery from major surgeries like opening and closing the rib-cage, bone operations, or removal of the uterus or gall bladder, done under general anaesthetic and with effective use of pain killers after the operation; surgical procedures on conscious animals but with the use of local anaesthetics to prevent pain during the operation and other pain killers after it; movement of excitable free-range domesticated livestock to unfamiliar housing.
Moderate suffering or noxiousness. Procedures require good justification.
Grade C
Procedures which cause marked anxiety, fear, pain or distress where any suffering caused is ended by euthanasia or by therapeutic or other interventions before it becomes excessive or where the suffering is short-lived and complete recovery can occur. Experiments which cause moderate anxiety, fear, pain or distress for long periods.
For instance: recovery from major surgery done under general anaesthetic but without the use of pain killer after the operation (e.g. reference animals used in studies to test how well particular pain killers work after surgery done under anaesthetic); marked social or environmental deprivation; capture, handling, restraint or housing, without the use of tranquillisers, of wild or semi-domesticated animals that exhibit marked flight responses.
Severe suffering or noxiousness. Procedures require strong justification.
Grade X
Procedures which cause severe, inescapable or unrelieved anxiety, fear, pain or distress where the intensity or duration, or both, of the induced suffering are at or beyond the limits of reasonable endurance.
For instance: conducting major surgery without the use of anaesthesia (e.g. where the animal is immobilised physically or with muscle relaxants); testing the effectiveness of pain-killers (analgesics) in animals with induced severe pain.
Very severe suffering or noxiousness. Procedures require the most exceptional justification.
Reduction. The main question here is:
"How can the number of animals used be reduced to the minimum needed to achieve the aim(s) of the work?"
This can be done in several ways:
If related but different work has been done before, it can be used to assess the number of animals that will need to be studied to produce a definite result.
Science-based statisticians can advise on the minimum numbers required.
In some situations, the animals can be studied during spontaneous occurrences of the illness or injury or other phenomena of interest, so that no extra animals are required for the purposes of the study.
Some studies can be done, painlessly and with no distress, in animals which have been studied for other scientific purposes. That can occur during a short period of unconsciousness while they are under anaesthetic just before they are euthanased using an overdose of that anaesthetic, or immediately after euthanasia.
Tissues from animals killed in abattoirs can also be retrieved immediately after death and used for research, teaching or testing, thereby avoiding the need to use extra animals.
Refinement. The question here is:
"How can the noxiousness of each study be minimised?"
There are many different ways of refining procedures.
For example, studies can involve:
non-invasive behavioural observations of conscious animals;
non-invasive methods such as ultrasound scanning or X-ray examinations or other sophisticated imaging techniques in conscious animals;
non-invasive methods such as external collection of urine and faeces;
limiting the invasiveness by taking blood samples using a needle the minimum number of times required to achieve the desired goals;
a hormone implant is placed under the skin using local anaesthesia instead of, for example, surgically modifying the animal to change the way it produces the hormone;
the animals are kept unconscious with a general anaesthetic throughout the study at the end of which they are killed with an overdose of that anaesthetic — unconscious and dead animals cannot suffer or experience pain;
anaesthetics, pain-killers (analgesics), sedatives and/or tranquillisers are used to relieve anxiety, fear, pain or distress in conscious animals;
any surgery on the animals is done by expert surgeons and great care is taken to keep damage to body tissues to an absolute minimum, thereby reducing any pain experienced when the anaesthetic used during the surgery wears off;
when the animals are likely to experience pain, suffering or other harm (e.g. in studies of diseases), their condition is assessed very regularly, the earliest signs that the study objectives have been met are identified, and the animals are withdrawn from the study or euthanased at that earliest time.
Also animals are handled gently throughout and, where possible, are given extra attention, including food treats and stroking, to enhance their well-being.
Replacement. There are three important questions here.
What alternatives can be used instead of higher order animals?
When is it appropriate scientifically to use alternatives to higher order animals?
When is it not appropriate scientifically to use alternatives to higher order animals?
What alternatives are available?
Non-animal alternatives
Alternatives derived from animals
Lower order animals:
Higher order animals:
Human beings:
When can alternatives to whole animals be used?
The answer is: when the alternative to animal use can genuinely reveal new knowledge or demonstrate particular features of the body organ or tissue or the whole body processes of interest. To date, replacement alternatives have been used extensively in teaching and during some stages of drug and cosmetic testing, but less extensively during research designed to understand how the body as a whole works. Computer, mathematical and other models are helpful for analysing, presenting or accessing knowledge we have already obtained about body processes, but they are less helpful in generating new knowledge.
When is it not appropriate to use alternatives to whole animals?
When chemical or computer or physical or mathematical models cannot reveal relevant new knowledge or demonstrate the known fact or principle.
When microbial or tissue cultures cannot be applied to achieve the desired goals.
When the processes to be studied or demonstrated cannot be effectively modelled using non-vertebrate or lower vertebrate animals.
When the processes to be studied or demonstrated can only be modelled (link to Animal models) effectively using the chosen species of higher order animal — e.g. when functions in the particular chosen species (e.g. sheep) closely parallel functions in another animal species (e.g. goats, cattle) or in human beings.
When the processes to be studied relate explicitly to the chosen species of higher order animal (e.g. studies of pregnant sheep to reduce death or sickness in newborn lambs).
Research using animals has various aims, including:
Improving the health and well-being of people.
Improving the health and welfare of entertainment, recreational, sport, and service animals, and animals used to provide therapeutic support.
Improving the health, welfare and productivity of farm animals and other production animals.
Finding better ways to preserve, protect and manage a range of animal species (especially endangered and native animals) in order to maintain a balance that is ecologically stable and well adapted to the New Zealand environment.
Developing more humane and effective pest control methods to protect endangered animals and plants from the species that threaten them and to prevent damage to the environment.
Broadening the foundations of biological science, including our knowledge and understanding of life processes in all animal species.
Teaching. The knowledge we gain about animals and people through research needs to be passed on, now and in the future, to those who are or who will become:
Doctors, nurses and other human health professionals.
Animal care personnel, veterinarians, farmers, conservation managers, zoo keepers and others engaged in animal-related activities.
School, polytechnic and university teachers; researchers in animal-based science.
Anyone interested in how his or her own body works or in what the welfare needs of animals are, and those interested in the coexistence of animals and people.
All such education involves describing, explaining and demonstrating how the bodies of animals and people work and how the functions of the body can be modified to benefit animals or people. Teachers are required to apply the Three Rs Principle whenever they consider using animals during a teaching exercise.
Testing is done as a check on the safety of new drugs or substances for human or animal use, and to check whether new batches of drugs and other agents like vaccines work. There is a legal requirement to test how safe and effective chemicals, drugs and other therapeutic agents are before they can be sold. Well-known tests that cause suffering when the test substance is poisonous, corrosive or otherwise harmful are the LD50 Test and the Draize Eye Irritancy Test. All three of the Three Rs have been successfully applied to testing and scientists are working hard to find more and better ways of applying them. For instance, replacement of animals with tissue cultures (cells kept alive in a test tube) is now used extensively, especially in the early stages of testing when whole animals were once used. Also, employing careful statistical analysis and substitutes for animals (replacements) have markedly reduced the number of animals required in testing procedures, and using earlier more humane endpoints thereby ending a noxious testing procedure much sooner than used to be the case is a form of refinement.