Metabolic modes indicative of carbohydrate status in the dairy cow.

Three modes of metabolism, indicative of differing levels of carbohydrate sufficiency, can be identified in nonpregnant dairy cows. The metabolic parameters defining these modes include: the hepatic content of glycogen and glucogenic metabolites; the in vivo net exchange of glucose and propionate across the liver, and of lactate and pyruvate across the liver and gut; and the concentration of insulin in the blood, and the secretion rate of insulin. In descending order of carbohydrate sufficiency, the three modes are; mode I, seen in fed nonlactating cows; mode 2, seen in fed lactating cows; and mode 3, seen in fasted or ketotic cows. The modes are interconvertible, because fasting will transform modes 1 or 2 into mode 3, while administration of either glucose, propionate, or glucocorticoid will, on the basis of at least one index, transform modes 2 or 3 into mode 1. It is concluded that a) carbohydrate sufficiency is jeopardized in lactating cows, and b) one reason for the therapeutic efficacy of antiketogenic agents used in the treatment of bovine ketosis is the ability of these compounds to increase carbohydrate sufficiency.