Extrapolating meaningful scientific information from laboratory animals for the benefit of mankind is difficult and fraught with many problems. To aid in this work it is imperative that we minimize as many variables as possible from the scientific data. It is an accepted fact that we need healthy animals as disease, whether clinical or sub-clinical, can affect the immune response system and the biochemistry and physiology of the animal, thus giving confusing information.

1 Introduction1.1 THE CONCEPT OF ANIMAL CARE.Ethics and the developing demand for relevant legislationDuring the late 19th Century there was an increasing concern in the UK with respect to a aspects of illtreatment of animals. This was reflected in the thinking of the research community and in 1871 The British Association For the Advancement of Science issued a set of basic principles of animal experimentation.This was a response to the growing awareness by the BA of the need for an ethical approach to biomedical research and for the considerate treatment of laboratory animals.

1 Introduction1.1 THE CONCEPT OF ANIMAL CARE.Ethics and the developing demand for relevant legislationDuring the late 19th Century there was an increasing concern in the UK with respect to a aspects of illtreatment of animals. This was reflected in the thinking of the research community and in 1871 The British Association For the Advancement of Science issued a set of basic principles of animal experimentation.This was a response to the growing awareness by the BA of the need for an ethical approach to biomedical research and for the considerate treatment of laboratory animals.

IntroductionWorking with laboratory animals is a privilege and those of us involved must accept the stewardship entrusted to us and always exercise our responsibilities to ensure that the moral, ethical and environmental concerns of these animals are always prominent in our actions. Laboratory animals should only be used when there is no known allernative, so all in-vitro methods must always be considered before an animal is used.

Today's sophisticated biomedical research sometimes requires the use of laboratory animals raised in stable micronen vironments free from the microorganisms that may compromise the success of an experiment. Laboratory rodents can be obtained in one of several categories defined by the degree to which they harbour microflora, whether commensal, potentially pathogenic or pathogenic. It is now possible to specify the different species of organism that are tolerated and those that are not tolerated, In such model laboratory animals it is essential to raise and maintain them in circumstances under which microorganisms that would not be tolerated cannot enter the production system.