Why Animals are Used in Research

Animals have unique and important roles in biomedical and behavioral research. Many medical advances that enhance the lives of humans are developed from research studies with animals.

Good animal care and good science go hand in hand. NIH takes the involvement, role, and respectful use of animals in research seriously. The integrity of the research depends on ensuring that they are well cared for throughout the research process. Of note, NIH does not support research into cosmetic testing.

Scientists thoughtfully and carefully choose and justify the specific animal models used in research based on their similarity to humans in anatomy, physiology, and/or genetics, or even everyday living conditions. Animals serve as “models” that represent certain aspects of a biological phenomenon to study. There are also times when certain animal models are used, like fish and frogs, whose anatomy and physiology may be quite different from humans, but still can help researchers address fundamental biological processes similar across species to develop knowledge to improve human health.

Animals used in basic research can help researchers understand important biological and physiological processes. This understanding may inform how we can better prevent, diagnose, treat, and cure diseases. Likewise, clinical trials involving animals, such as in the Comparative Oncology Program , shed light on risk factors common to people. The tools and treatments resulting from this research are then used to improve the lives of humans.

When researchers develop hypotheses (which are scientifically backed ideas) about the possible causes of diseases and potential treatments, these hypotheses must be evaluated very carefully so that benefits and risks from the proposed new approaches are clearly understood. When necessary, new hypotheses are tested in animal models first to gather sufficient evidence of these benefits and risks before considering use in humans or additional animals. Also, translational research often involves preclinical trials on animals before clinical trials with human participants can begin.

Animal studies conducted in the laboratory allow scientists to control factors that might affect the outcome of the experiments. This includes factors like temperature, humidity, light, diet, or medications. Even the genetics of many animal models can be known and well understood, so only the factor being tested is changed and examined. These rigorous controls allow for more precise understanding of biological factors at hand and provide greater certainty about experimental outcomes when developing treatments. The findings also move the scientific process forward, setting the stage for future research and studies in humans. This is called translational research. Though not all research with animal models may result in human treatments, some research builds fundamental knowledge to enhance our understanding of physiological systems. This includes research to understand what might contribute to unexpected outcomes within animal research and to develop new models of health and disease.

Scientists must clearly explain why animals are necessary for their research and that the minimal number needed to ensure rigor and reproducibility will be used when proposing ideas to NIH for funding and throughout the research activity itself. Every NIH-funded activity involving live vertebrate animals must describe in their NIH grant application:

• How it is scientifically important, hypothesis driven, and relevant to public health
• What specific animals and how many will be involved as well as why they were selected
• Why the specific animal is appropriate for the questions being asked
• A complete description of all procedures that will be performed on the animals
• How any potential discomfort, distress, injury, and pain the animals may experience will be minimized
• Why the study cannot be done using another model or approach
• The research findings and outcomes, and their potential benefits

After the NIH-supported research is completed, we support the research institution’s interest in adopting out their research animals, should they choose to do so. While NIH funds may not be allowed to directly support these efforts, we developed a webinar to help research facilities create an adoption program.