Three Rs Introduction
Three Rs: Replacement, Reduction and Refinement
Animal welfare and the potential for pain and distress to be experienced by animals used in
science have concerned the general public and thoughtful researchers for a long time. It was
these concerns, together with increasing use of animals in fundamental and applied research
that motivated W.M.S. Russell and R.L. Burch to examine how decisions should be made about
such use of animals. In the book The Principles of Humane Experimental Technique, first
published in 1959, Russell and Burch proposed the concept of the Three Rs. The Three Rs stand
for Replacement, Reduction and Refinement. Over the past 40 years the Three Rs have become
widely accepted ethical principles, and are now embedded in the conduct of animal-based
science in Canada and throughout many countries in the world.
Alternatives
The term "alternatives" was coined by the distinguished physiologist David Smyth in his 1978
book Alternatives to Animal Experiments. It is used to describe any change to established
scientific procedures that will result in the replacement of animals, a reduction in the
numbers used or a refinement of techniques that may minimize harms to the animals. Therefore,
Smyth's term "Alternatives" is synonymous with Russell and Burch's "Three Rs".
The CCAC's ethic of animal experimentation is based on Smyth's definition of Alternatives,
i.e. Replacement, Reduction and Refinement.
Replacement alternatives refers to methods which avoid or replace the use of animals in
an area where animals would otherwise have been used. This includes both absolute replacements
(i.e. replacing animals with inanimate systems, such as computer programs) and relative
replacements (i.e. replacing more sentient animals, such as vertebrates, with animals that
current scientific evidence indicates have a significantly lower potential for pain
perception, such as some invertebrates).
Reduction alternatives refers to any strategy that will result in fewer animals being
used to obtain sufficient data to answer the research question, or in maximizing the information
obtained per animal and thus potentially limiting or avoiding the subsequent use of additional
animals, without compromising animal welfare.
Refinement alternatives refers to the modification of husbandry or experimental
procedures to minimize pain and distress, and to enhance the welfare of an animal used in
science from the time it is born until its death.
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Implementation of the Three Rs
The CCAC requires principal investigators to implement the Three Rs when they are preparing to
use animals for a scientific purpose. Investigators must consider whether animals are required
or whether suitable replacement alternatives exist. When animals are used, the investigator
must consider how best to decrease the number of animals used to a minimum and/or how to
maximize the amount of information obtained per animal (Reduction alternatives), and must
identify potential harms and ways to minimize these (Refinement alternatives). Consideration
of the Three Rs will start during the early stages of research planning, together with
development of the experimental protocol (rather than as a last minute addition).
For more background information on the Three Rs, the following resources may be useful:
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