Abstract
This chapter provides an overview of germfree (GF), gnotobiotic (GN), and defined flora (DF) laboratory rats, relating their history, traditional and modern derivation procedures, the anatomy and physiology, and their use in the study of mammalian host–microbiome relationships. Extensive literature on the nutrition and physiology of GF rats and the expanding library of immunological reagents have increased the research utility of GF, GN, or DF rats. Such rats have been extensively used in metabolic experiments as nucleus seed stocks for the production of disease-free animals and as tools for infectious disease studies, among others. The chapter also presents research applications of GF rats that are particularly suitable for testing candidate viral carcinogens since they are uniquely free of all known viruses, for pathology studies in the distinguishing of primary mediation lesions from those associated with infections, and the study of the biological effects of radiation.