THE CHANGING ROLES OF INSULIN DURING THE TRANSITION PERIOD

摘要

The overall profitability and health of dairy cattle benefit from successful management during the transition period (Drackley, 1999). The metabolic adaptations that support the onset of lactation include increased mobilization of fatty acids from adipose tissue and increased hepatic gluconeogenesis (Bell, 1995). Orchestration of nutrient partitioning is necessary to meet new metabolic demands corresponding with a simultaneous decrease in dry matter intake around calving, requiring mobilization of body fat reserves (Bauman and Currie, 1980). These responses increase circulating non-esterified fatty acids (NEFA), which when taken up by the liver in excess induce triglyceride accumulation and increase risk for fatty liver and other disorders such as ketosis, milk fever, retained placenta, and mastitis (Goff and Horst, 1997). Many of these relationships relate to the changing roles of insulin. A more thorough understanding of these roles may enable us to continue to improve the management of transition dairy cattle and further reduce the incidence of metabolic disorders.