[Estimation of insulin and glucose regulation in the dairy cow using daily profiles, simple and modified glucose tolerance test]

Insulin and glucose regulation plays a central role in regulating distribution of metabolites between udder and body tissues and, consequently, in ensuring optimum adjustment between milk yield and health stability. An experimental study was conducted into four dairy cows, between 17 weeks before and 52 weeks after calving to establish six diurnal profiles for insulin and glucose concentrations in blood plasma and undertake 18 glucose tolerance tests, nine of them simple and nine modified. The three methods used in examination provided differentiated but complementary data on the glucose-insulin system of dairy cow. Flow of metabolites in the mammary gland, in early lactation, was found to be supported by low insulin concentrations in blood plasma, reduced pancreatic response to insulinogenic stimuli, and decreased responsiveness of peripheral cells to insulin. Endocrine adaptation to catabolic metabolism had its onset as early as several weeks before calving. Alterations to insulin concentrations in blood plasma as well as to pancreatic reactivity to insulinogenic stimuli and to responsiveness of peripheral cells to insulin were found to take place at various junctures. It should be proved to use the common and modified glucose tolerance test for the description of the individual metabolic type of each single dairy cow.