METABOLIC CHARACTERISTICS OF INDUCED KETOSIS IN NORMAL AND OBESE DAIRY-COWS

Four groups of 6 cows were used to determine the effects of body condi tion on induction of ketosis. At calving, obese cows were heavier by 1 08 kg and had a higher body condition score by 0.74 units than did nor mal cows. Susceptibility to induced ketosis was evaluated by restricti ng dry matter intake by 20% and feeding 7% 1,3-butanediol from 15 to 4 9 d in milk (DIM) to one group of obese cows and to one group of norma l cows. No normal or obese cows fed the control diet developed ketosis . Two normal and 2 obese cows developed ketonemia because of the induc tion 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-but anediol lost 15% more body weight than did cows fed the control diet d uring the induction period. Concentrations of nonesterified fatty acid s increased at parturition, peaked at 7 to 14 DIM, and returned to pre partum concentrations by 21 DIM. Plasma beta-hydroxybutyrate concentra tions increased after calving and was increased additionally by the in duction protocol. At the onset of lactation, plasma insulin decreased, plasma glucagon increased, hepatic triacylglycerols increased, and he patic glycogen decreased. The incidence of ketonemia and clinical keto sis was the same for obese and normal cows, but, on the basis of chang es of blood and liver composition, incidence of ketosis would probably increase if obese cows were overfed throughout the entire dry period.