The rat model has been useful in determining the role of nutrients in such mammalian developmental processes as maturation of the brain and gastrointestinal tract and metabolic adaptation in the liver. The suckling period, a critical time in early development, has been intractable to classical nutritional studies because of the necessity of the maternal involvement in rearing the pups. In this article, we review a promising technique in which rat pups are artificially reared through the use of an intragastric cannula connected to an automated pump that delivers a milk-substitute formula. We present relevant details of this technique, highlighting some of its advantages and limitations. Three metabolic processes in different organs are presented as examples of the usefulness of the artificial-rearing technique. This technique has high potential for a wider range of applications in nutritional assessment of macro- and micronutrients and in metabolic regulation in rats during the early postnatal period.