Effects of starvation on intermediary metabolism in the lactating cow. A comparison with metabolic changes occurring during bovine ketosis

Abstract

1. The purpose of this study was to determine the nature of the metabolic changes associated with carbohydrate and fat metabolism that occurred in the blood and liver of lactating dairy cows during starvation for 6 days. 2. During starvation, the blood concentrations of the free fatty acids and ketone bodies increased, whereas that of citrate decreased. After an initial increase, the blood concentration of glucose subsequently declined as starvation progressed. Starvation caused a significant decrease in the plasma concentration of serine and a significant increase in that of leucine. 3. After 6 days of starvation the hepatic concentrations of oxaloacetate, citrate, phosphoenolpyruvate, 2-phosphoglycerate, 3-phosphoglycerate, glucose, glycogen, ATP and NAD(+) had all decreased, as had the hepatic activities of phosphopyruvate carboxylase (EC 4.1.1.32) and pyruvate kinase (EC 2.7.1.40). 4. The above metabolic changes are similar to those previously found to occur in cows suffering from spontaneous ketosis (Baird et al., 1968; Baird & Heitzman, 1971). 5. Milk yield decreased progressively during starvation. 6. There were marked differences in the ability of individual animals to resist the onset of severe starvation ketosis.

Effects of food deprivation on ketonaemia, ketogenesis and hepatic intermediary metabolism in the non-lactating dairy cow

“…However, in spite of the absence of any marked ketonaemia, food deprivation of the nonlactating cows had produced changes in the concentrations of hepatic metabolites that were qualitatively similar to those seen previously in the fooddeprived lactating cows of Baird et al (1972) that became severely ketotic. This was investigated further by monitoring ketone-body production by the liver and gut in vivo in appropriately catheterized animals.…”

“…3. During the food deprivation, blood ketone-body concentrations rose significantly, but to a value that was only 16 % of that achieved in lactating cows deprived of food for 6 days [Baird, Heitzman & Hibbitt (1972) Biochem. J.…”

“…B by the observation in two catheterized non-lactating cows that, although there was a 2-fold increase in hepatic ketogenesis during 6 days of food deprivation, ketogenesis from the splanchnic bed as a whole (i.e. gut and liver combined) declined slightly owing to cessation of gut ketogenesis.Robertson et al (1960) andBaird et al (1972) demonstrated that mature cows that are in the early stages of lactation, i.e. about 25-50 days post partum, develop severe ketonaemia when deprived of food for 4-6 days.…”

“…*Present address: Biological Laboratory, University of Kent, Canterbury, Kent CT2 7NJ, U.K. Vol. 178 Baird et al (1972) found that the induction of ketosis in lactating cows by means of food deprivation was associated with major changes in the hepatic steady-state concentrations of a variety of metabolites, including intermediates of the tricarboxylic acid cycle and the Embden-Meyerhof pathway, ATP and NAD+. These changes were very similar to those previously found to be associated with spontaneous ketosis (Baird & Heitzman, 1971), and it was concluded that the changes in metabolite concentration, particularly the fall in the concentrations of glycogen and of intermediates of the tricarboxylic acid cycle, were a necessary prerequisite for elevated hepatic ketogenesis.…”

Lactation, pregnancy and metabolic disorder in the ruminant

“…Integration of metabolism 1 1 9 difference appears to be that during the fast milk production falls more slowly in the susceptible cows (Baird et al 1972).…”