Ethical review always required by lawIn all applications involving animal research submitted to an Ethical Committee on Animal Experiments, the researcher must motivate why he or she selected a particular animal species. Government agencies also require that drugs used in humans be tested in at least two types of animals, one of which is not a rodent. The reason is that a drug can have different effects on different types of animals.
Similar to humansIf the aim is to use animals as models for a function or a disease that affects humans it can be appropriate to choose an animal that is similar to humans in that context. For example, in many respects a pig´s cardiovascular system is more similar to the human cardiovascular system than a dog´s would be. Consequently, in studies of myocardial infarction, researchers could find pigs much more useful than dogs.
Previous research on animal type — an important factorTraditions and routines often help determine the animal type chosen. If a particular animal type has been studied extensively, a large body of material and experience would be available on how that type of animal functions and what values are considered normal. This often helps the researcher draw conclusions in a new study and is one reason why some animal types, e.g. rats, have become more popular than others as laboratory animals.
Small animals expensive — large animals even more expensiveEconomic aspects often determine the type of animal that can be used in research. For instance, mice are much cheaper to manage than large animals. At times researchers must use animals of a particular size. When surgeons practice heart surgery it helps if the animal´s heart is approximately the same size as a human heart.
On the other hand, it could be difficult to use a large laboratory animal to test a new drug. In early stages of drug development researchers often have a small amount of the drug, which might be insufficient for large animals. Furthermore, the drug could be expensive, and it would be cheaper to deliver smaller amounts to smaller animals.
For the animal´s sakeAnimal research is often conducted on behalf of the species, particularly for pets and farm animals. Such animal research can yield findings that may be useful in the care and management of other animals in the same species. Horse, chickens, and cows are used as laboratory animals, for example, to help the animals feel better and so we can learn more about their behaviour and how to care for them. Animals also need vaccines and drugs to prevent or cure disease. Since many farm animals are used in food production it is important to understand how quickly drugs exit the body, so we can produce food that is safe for human consumption. The following examples describe various animal types and how they are used in research. However, the list is not complete since the choice of animal type depends on many different factors.