**Abstract**

This chapter will focus on cellular regulatory programs implemented by the ruminant physiology in order to respond to external stimuli such as nutrition as well as important physiological events such as parturition. The increasing adoption of "omics" technologies and bioinformatics in nutrition and physiology in ruminant research have allowed us to delineate a clearer picture on what regulates major biological process at a molecular level such as milk synthesis and meat quality and fatty acid composition as well as pathological conditions such as ketosis, mastitis, and heat stress. The assembly of such plethora of information in a blend among nutritional research, molecular biology, and novel tools to study the response of the genome to nutrition has led to emerging disciplines such as nutritional genomics or "nutrigenomics."

**Keywords:** nutrigenomics, transcription factors, ruminants
