Blood plasma glucose, lactate and nonesterified fatty acid responses to adrenaline infusions in early and mid lactation in dairy cows fed crystallinefat or free fatty acids

This study tested the hypothesis that adrenaline has different effects on b lood plasma glucose, lactate and nonesterified fatty acid (NEFA) concentrat ions in early and mid lactation and that the feeding of crystalline fat (co nsisting of triglycerides) and free fatty acids (FFA), compared with a star ch-rich ration, modifies the effects of adrenaline in dairy cows. Glucose, lactate and NEFA responses to intravenously infused adrenaline [15 mu g/kg x (min) for 10 min] were studied in weeks 9 and 19 of lactation in cows who se diets were supplemented with crystalline fat or FFA or a starch-rich rat ion. Concentrations of glucose, lactate and NEFA rapidly increased up to 15 min after the starr of adrenaline infusions. Glucose responses to adrenali ne were comparable in weeks 9 and 19 of lactation, whereas the lactate resp onses were smaller, and those of NEFA were greater in week 9 than in week 1 9 of lactation. As the feeding of crystalline far, FFA or a starch-rich rat ion did not modify the effects of adrenaline on glucose,lactate or NEFA, th e target tissue sensitivity and/or responsiveness to adrenaline had obvious ly not been changed.