Systems physiology in dairy cattle: nutritional genomics and beyond.

Microarray development changed the way biologists approach the holistic study of cells and tissues. In dairy cattle biosciences, the application of omics technology, from spotted microarrays to next-generation sequencing and proteomics, has grown steadily during the past 10 years. Omics has found application in fields such as dairy cattle nutritional physiology, reproduction, and immunology. Generating biologically meaningful data from omics studies relies on bioinformatics tools. Both are key components of the systems physiology toolbox, which allows study of the interactions between a condition (e.g., nutrition, physiological state) with tissue gene/protein expression and the associated changes in biological functions. The nature of physiologic and metabolic adaptations in dairy cattle at any stage of the life cycle is multifaceted, involves multiple tissues, and is dynamic, e.g., the transition from late-pregnancy to lactation. Application of integrative systems physiology in periparturient dairy cattle has already advanced knowledge of the simultaneous functional adaptations in liver, adipose, and mammary tissue.