This chapter reviews advances in nutrigenetics and nutrigenomics and their relevance to modern dairy cattle production. Together, these disciplines extend nutrition research toward a systems-level, “feedomics”, integrating diet composition, host genetics, physiology, and the ruminal microbiome. The chapter outlines key regulatory mechanisms, including transcription factor activation, epigenetic programming, and non-coding RNA control, operating across tissues central to lactation and health. Methodological advances in transcriptomics, proteomics, metabolomics, single-cell analyses, and genome editing are critically discussed, with an emphasis on experimental rigor and data integration. Physiological applications are highlighted, particularly during the peripartal period, where nutrigenomic insights reveal tissue-specific adaptations to energy balance, immune stress, and oxidative challenges.