Role Of Phosphoenolpyruvate Carboxykinase in Periparturient and Ketotic Dairy Cows
Jennifer S. Duncan, Diane J. Carroll and C. Y. Hu
Department of Animal Sciences, Oregon State University, Corvallis, April, 1998
Research Question
Ketosis affects 2 to 15% of cows on U.S. dairies resulting in significant losses in milk production. Cows are most susceptible to ketosis during the early postpartum period because dry matter intake may not meet the energy demands of high milk production. Symptoms of ketosis include low blood glucose and elevated blood non-esterified fatty acid (NEFA) and ketone (BHB) concentrations. The ability to predict and prevent ketosis would greatly reduce financial losses to the producer.
The goal of this study is to examine the ability of the prepartum liver enzyme phosphoenolpyruvate carboxykinase (PEPCK) to predict the likelihood that postpartum ketosis will occur.
Summary
Although the occurrence of ketosis is a postpartum phenomenon, recent studies have focused on the prepartum period as key in the development of the disorder. Depressed dry matter intake and elevated blood non-esterified fatty acids concentrations during the 2 to 3 weeks prior to calving have been associated with the occurrence of postpartum ketosis. Hepatic PEPCK is an enzyme that is key in the regulation of blood glucose levels and the mobilization of body fat. Therefore, PEPCK may prove to be a sensitive indicator of energy status and cow susceptibility to postpartum ketosis.
Study Description
Thirty-four pregnant multiparous Holstein dairy cows were fed a single prepartum diet that met NRC (1989) requirements. At calving, cows were transitioned onto either a control (n = 13) or 3.5% supplemental fat (n = 21) diet for three weeks. Liver tissue biopsies were collected and analyzed for PEPCK mRNA and activity.
Applied Questions
How many of the cows experienced ketosis after calving?
About 40% of the cows fed either the control or fat-supplemented postpartum diet experienced ketosis over the first three weeks postpartum.
What were the characteristics of cows that had ketosis during the second and third week after calving?
| No ketosis | Ketosis | |
| Cow, numbers | 20 | 14 |
| BHB, mg/dl | 9.2 | 23.6 |
| Glucose, mg/dl | 49.0 | 43.6 |
| NEFA, uM | 717 | 1374 |
Did cows that became ketotic postpartum have lower dry matter intake or higher NEFA concentrations prepartum?
This study did not confirm the results of other studies that showed a drop in prepartum dry matter intake and blood NEFA concentrations for cows that experienced ketosis in the postpartum period compared to cows that were healthy.
Were there prepartum differences between the postpartum ketotic and non-ketotic cows?
Cows that experienced ketosis had lower hepatic PEPCK activity prepartum (6.6 vs. 9.3 units/min/g protein) compared to cows that did not experience ketosis postpartum. Each unit decrease of prepartum hepatic PEPCK activity doubled the likelihood of the occurrence of postpartum ketosis.
Conclusion
Our data indicates that hepatic PEPCK activity is a useful prepartum predictor of cow susceptibility to ketosis.
