Metabolic characteristics of induced ketosis in normal and obese dairy cows.

Four groups of 6 cows were used to determine the effects of body condition on induction of ketosis. At calving, obese cows were heavier by 108 kg and had a higher body condition score by 0.74 units than did normal cows. Susceptibility to induced ketosis was evaluated by restricting dry matter intake by 20% and feeding 7% 1,3-butanediol from 15 to 49 d in milk (DIM) to one group of obese cows and to one group of normal cows. No normal or obese cows fed the control diet developed ketosis. Two normal and 2 obese cows developed ketonemia because of the induction protocol, and 1 cow in each of the two groups developed clinical ketosis. Obese cows lost 59% more body weight during the first 14 DIM than did normal cows, and cows fed the restricted diet plus 7% 1,3-butanediol lost 15% more body weight than did cows fed the control diet during the induction period. Concentrations of nonesterified fatty acids increased at parturition, peaked at 7 to 14 DIM, and returned to prepartum concentrations by 21 DIM. Plasma beta-hydroxybutyrate concentrations increased after calving and was increased additionally by the induction protocol. At the onset of lactation, plasma insulin decreased, plasma glucagon increased, hepatic triacylglycerols increased, and hepatic glycogen decreased. The incidence of ketonemia and clinical ketosis was the same for obese and normal cows, but, on the basis of changes of blood and liver composition, incidence of ketosis would probably increase if obese cows were overfed throughout the entire dry period.