ABSTRACT
The usefulness of the germfree animal in the study of true genotypical potential was clearly demonstrated in a paper by V. du Vigneau et al. that appeared in 1951 in the Journal of Nutrition. The many differences in function and metabolism between germfree and conventional rodents express the difference between the two phenotypes, if care has been taken to keep genotypes in as close a proximity as possible. Major causes of these differences can be found in the “enlarged cecum syndrome”, and in the qualitative and quantitative differences of the challenges to the immune system. The body of the ad libitum-fed rat contains a sizable amount of brown adipose tissue which, via adrenergic stimulation, contributes significantly to the control of its energy metabolism. Major effects are produced by the intestinal microflora on cholesterol and bile acid metabolism which directly and/or indirectly affect many aspects of intestinal function and intermediary metabolism. Differences in intermediary metabolism will affect cholesterol and bile acid metabolism.
