METABOLIC CHANGES IN DAIRY-COWS WITH KETONEMIA IN RESPONSE TO FEED RESTRICTION AND DIETARY 1,3-BUTANEDIOL

The objective was to measure progressive changes in metabolism of cows during a protocol that induced subclinical ketosis. From d 14 to 42 postpartum, 13 Holstein cows were in either a control group (6 cows) or a ketosis induction group (7 cows) that was restricted to 80% of ad libitum intake and fed 1,3-butanediol (7% of DM). Six ketosis induction cows developed ketonemia but not clinical ketosis; cow 7 developed clinical ketosis. Milk production was less, but fat content was greater, for ketonemic cows. Energy balance reached a nadir of -7.2 Mcal/d at d 21 for ketonemic cows, whereas controls reached energy equilibrium at d 28. Concentrations of NEFA in plasma and of beta-hydroxybutyrate in whole blood increased during ketonemia. Dextran sulfate-precipitable cholesterol and triglyceride in serum were increased only at d 21 and not at d 28, 35, 42, or 49. Concentrations of glycogen, total lipid, triglyceride, and cholesterol in liver increased during ketonemia. Oxidation of palmitate to CO2 was greater at d 21 in liver slices from ketonemic cows, whereas oxidation to acid-soluble products remained constant for those cows but decreased for controls. The ketonemic cows had lower weight ratios of triglyceride to glycogen in liver during pretreatment than those that became clinically ketotic in earlier studies (.5 vs. greater-than-or-equal-to 1.8). Susceptibility to clinical ketosis, therefore, may be indicated by increased hepatic triglyceride to glycogen ratios during the peripartal period.