Animal models have helped make enormous discoveries and breakthroughs in the last few decades. From Pasteur’s use of sheep to test the ‘Germ Theory’, Pavlov’s classic conditioning experiments in dogs, to Dolly the first cloned mammal, animal research has come a long way. Today, most drugs, vaccines and other pharmaceutical products for medical use are initially tested and validated in laboratory animals. In addition to medicine development, basic research uses a number of animals to study genetic, cellular, and molecular systems, physiology, and organ systems as well as behavior and evolution.

The guiding principles for ethical treatment of animals in testing and experimentation were first introduced by Russell and Burch in 1959 and are known as the three Rs: Replacement, Reduction and Refinement.1,2

1. Replacement

  • Replace higher model organisms with lower ones, for example, use non-sentient beings (sentience can be described as the ability to be conscious, perceive pain or suffering and experience subjectivity).
  • Where possible, adopt in vitro or in silico alternatives such as:
    • Cellular fractions, whole cells, tissues or organs in culture, animal products
    • Mechanical or computer modelling that can simulate human biology or predict pharmacological properties of drugs
    • Artificial animals (dummies) and audio-visual aids to teach dissection and anatomy and to demonstrate protocols
    • Micro-dosing and clinical testing in humans
    • An interesting alternative to the use of animals to teach and practice surgeries in medical schools is the advent of the human-patient simulators that have a realistic human anatomy and physiology and can be programmed to bleed, breathe, convulse, and so on like humans.3,4

Various institutions and governing bodies have journals, websites, and databases that provide information and resources on alternatives to animal testing (e.g., ALTWEB,5 ALTEX,6 ALTBIB,7 DB-ALM8).

Replacement carries some disadvantages, though:

  • Complex systems cannot be studied using lower organisms
  • Research involving multiple cells or organ systems cannot be studied in vitro
  • Conducting behavioral studies can be challenging, if not impossible, without using whole animals
  • Not all in silico methods are equally reliable

Sometimes using animals might be difficult to avoid. In that case, you should strive to observe the second R.

2. Reduction

  • Design experiments properly and calculate the number of animals needed
  • Plan studies where animals can be used as their own controls
  • Share animals between experiments or research labs (same batch of controls or different organs from same animal for various purposes)
  • Collaboration with statisticians to get the best possible results with the lowest number of animals
  • Perform thorough literature searches and consult experienced researchers to avoid repeating experiments already performed
  • Encourage publishing of negative data to prevent unnecessary repetition of experiments
  • Plan sensible breeding strategies for animals to avoid an excess in supply that may not be used for experiments

Disadvantages of reduction: statistical analyses may be affected by a small sample size, and journal reviewers may ask for repeat experiments to get data that are more significant. Nevertheless, being conservative with the number of animals you choose to start out with is always a good way to observe good ethical behaviour

When you  conclude that animals have to be used for a certain experiment because no appropriate replacement exists and when no reduction of animals is possible (ruled out the first two Rs), then the third R becomes essential:

3. Refinement

  • Refine experiments and protocols to minimize pain and distress in animals
  • Refer to standard guidelines and regulations and determine appropriate end-points and termination criteria for experiments
  • Acquire and provide proper training for careful handling of animals
  • Learn to identify pain and distress signals in animals
  • Understand their normal as well as abnormal physiology and behavior
  • Use appropriate analgesics, anesthetics, and/or anti-inflammatory drugs for animals under testing
  • Use non-invasive experimental procedures as much as possible
  • Pay special attention to animals during post-surgical care
  • Identify alternatives to the commonly used pain and disease-inducing reagents (such as Freund’s adjuvant, toxins, allergens or infectious agents) and to procedures (like foot pad injections, toe clipping, retro-orbital blood collection, ascites production or tumor induction)
  • Consult animal technicians and veterinarians if in doubt about any procedure or technique used or about the health and response of animals

Disadvantages are that refinement strategies require additional resources, training, and efforts. However, none of these limitations are excuses to compromise animal quality of life and welfare.

While it would be desirable to see a complete stop in the use of animals in research, it does not seem possible in the near future. The only options currently available to us are to replace animal models with alternatives where possible. Also, researchers are working to gradually phase out animal use by reducing the numbers of animals used in ongoing research, striving to develop treatments that are more humane, and improving the welfare of the animals that absolutely must be used.

References and Further Reading:

  1. Johns Hopkins AltWeb –
  2. National centre for the replacement, refinement, and reduction of animals in research –
  5. ALTWEB –
  6. ALTEX –
  7. ALTBIB –
  8. DB-ALM –