Reconstruction of Metabolic and Physiologic Adaptations to Lactation Using Systems Biology

Along with functional bioinformatics, high-throughput 'omics' are the foundation of modern systems biology, a field of study widely used in model organisms (e.g., rodents, yeast, humans) to enhance understanding of the complex biological interactions within cells and tissues at the gene, protein, and metabolite level. The “systems approach” is particularly well-suited for the study of the interactions between nutrition and physiological state with tissue metabolism and function during key life stages of organisms such as the transition from pregnancy into lactation. This physiological state is often referred as the “periparturient” or “transition” period. In modern dairy cows with an unprecedented genetic potential for milk synthesis, the nature of the physiologic and metabolic adaptations during the periparturient period is multifaceted and involves the rumen and its microorganisms along with key tissues such as liver, adipose, mammary gland, and cells of the immune system. Application of the systems approach in periparturient cows already has allowed a better understanding of the degree of these multifaceted adaptations. Modern bioinformatics tools capable of discerning functional outcomes and biologically-meaningful networks complement the ever-increasing ability to generate large molecular, microbial, and metabolite data sets. The ultimate goal is to visualize the complexity of the systems under study and uncover key players involved in the cow’s adaptation to physiological state and nutrition.