Physiological and pathological adaptations in dairy cows that may increase susceptibility to periparturient diseases and disorders

Dairy cows undergo tremendous metabolic and physiological adaptations around parturition to support lactation. The liver is central to many of these processes, including gluconeogenesis and metabolism of fatty acids mobilized from adipose tis- sue. Fat accumulation may impair normal functions of the liver and increase ketogenesis, which in turn may predispose cows to other metabolic abnormalities. Several aspects of dietary management and body condition may alter these adaptations, affect dry matter intake, and increase or decrease susceptibility to periparturient health problems. Overfeeding energy dur- ing the dry period is a prominent risk factor. Considerable progress has been made in recent years in describing the adap- tive changes in the liver and other organs in normal and abnormal states, but this knowledge has not yet identified unequiv- ocally the key steps that might be compromised during development of metabolic disorders. The potential role of signaling compounds, such as the inflammatory cytokines released in response to environmental stressors, infectious challenge, and oxidative stress, in the pathogenesis of periparturient disease is under investigation. New techniques such as functional genomics, using cDNA or oligonucleotide microarrays, as well as proteomics and metabolomics, provide additional high- throughput tools to determine the effects of nutrition, management, or stressors on tissue function in development of dis- ease. Integrative approaches should be fruitful in unraveling the complex interactions of metabolism, immune activation, stress physiology, and endocrinology that likely underlie development of periparturient disease.