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.

1. The metabolism of trenbolone acetate, 17 beta-acetoxyestra-4,9,11-trien-3-one (TBA), an anabolic compound used as a growth promoter, was compared in rat and cow. 2. [6,7-3H] TBA was injected i.v. into rats and a heifer, and bile was collected for 24 h. In both species, the bile was the major route of excretion. TBA undergoes an extensive hydrolysis to 17 beta-hydroxyestra-4,9,11-trien-3-one and the unchanged compound was not detected, but subsequent major metabolic pathways are different in the two species. 3. In the rat, oxidation of the 17 beta-hydroxyl to the 17-oxo group and hydroxylation in the 16 alpha-position are the major routes. The three major metabolites are 17 beta-hydroxyestra-4,9,11-trien-3-one, 16 alpha, 17 beta-dihydroxyestra-4,9,11-trien-3-one and 16 alpha-hydroxyestra-4,9,11-trien-3, 17-dione. 4. In the heifer, 17 alpha-epimerization is the major pathway and the main metabolite is the 17 alpha-hydroxyestra-4,9,11-trien-3-one. 5. In both species, estra-4,9,11-trien-3,17-dione and the other metabolites, resulting either from hydroxylation in 1, 2, 6 beta, 16 alpha or 16 beta positions, or from aromatization of the A ring, were minor products. 6. Overall, 60% of the 3-oxotriene structures identified in the rat bile were 17 beta-hydroxylated and the remainder were 17-keto metabolites, whereas in the heifer bile 90% were 17 alpha-hydroxylated compounds. 7. Thus, in bovine species, the major pathway is similar to those of testosterone or 17 beta-estradiol which are mainly excreted as their 17 alpha-epimers. The epimerization strongly decreases the biological potency, as with the natural 17 beta-hormones, and leads to detoxication of tissue residues.

1. The hepatic concentrations of the ketone bodies and of metabolites and activities of enzymes involved in gluconeogenesis were measured in healthy lactating and non-lactating cows 48h after administration of Voren, an ester of dexamethasone, and compared with those found in control animals given saline. Parallel measurements were also made of the blood concentrations of several of the metabolites. 2. Blood glucose concentrations were raised in the Voren-treated animals, whereas blood ketone body and free fatty acid concentrations were unaltered. Similarly there was no change in the hepatic concentrations of the ketone bodies. 3. Significant increases were found in the hepatic concentrations of citrate, 2-oxo-glutarate and malate in both groups of animals given Voren. 4. The hepatic concentrations of those glycolytic intermediates that were measured either decreased or did not change after Voren treatment. 5. The enzymes aspartate transaminase and fructose 1,6-diphosphatase were unchanged in activity after Voren administration, whereas phosphopyruvate carboxylase (EC 4.1.1.32) activity was depressed in the lactating group. However, glucose 6-phosphatase, tryptophan oxygenase and tyrosine aminotransferase increased in activity. 6. In several cases those hepatic metabolites that increased in concentration after Voren administration were present in lower concentration in normal lactating cows than in normal non-lactating cows. The same applied mutatis mutandis to those metabolites that were decreased by Voren. 7. These findings are discussed in relation to the use of glucocorticoids in the treatment of bovine ketosis.

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