The study was performed in eight high-pregnant cows in which medium to high ketonuria was repeatedly detected. The control group consisted of six cows free from ketonuria before parturition. Blood and urine were sampled from the cows two to eight weeks before parturition, on the day of parturition, 24 hours, three to five days and two to six weeks after parturition. The concentrations of oxidated ketone bodies and beta-hydroxybutyrate were determined by the distilling method. Further, the values of clinico-biochemical parameters in the urine and blood were determined within the range of the preventive diagnosis system. No marked changes in the health condition were found by the current clinical examination. The average concentration of total ketone bodies in the blood of the cows two to eight weeks before parturition was 29.2 mg per litre; the respective values recorded in the control cows were lower by about a half. The concentration of ketone bodies in the blood of the cows in the experimental group decreased on the day of parturition. The decrease was followed by a gradual rise of the total ketone bodies content in the blood up to 50.6 mg per litre two to six weeks after parturition. Alterations testifying to a disorder in the function of liver were observed in the cows of both groups throughout the period under study. The disorder was due to excessive administration of crude protein to the high-pregnant cows combined with the use of low-quality silage. After parturition the feed ration was not differentiated according to performance and was deficient in the basic nutrients and vitamins. Ketonuria was obviously due to the simultaneous intensification of hepatal and alimentary ketogenesis, caused by hepatopathy in combination with the intake of large amounts of poor-quality silage containing butyric acid.