The effects of diet on some hepatic enzyme activities in the pre-ruminant and ruminating calf.

Three mild-replacer diets containing different amounts of lipid with differing fatty acid compositions were fed to pre-ruminant calves. These diets did not affect the specific activities of the hepatic enzymes, involved in carbohydrate and lipid metabolism, which were studied. With the onset of rumination there was a general decrease in the activities of the glycolytic enzymes and glucose-6-phosphate dehydrogenase (EC 1.1.1.43) and an increase in the activity of acetyl CoA synthetase (EC 6.2.1.1). In the ruminating calf the specific activities of some of the enzymes of carbohydrate metabolism were substantially greater on the concentrate diet than on the pelleted dried grass. In the case of glucose-6-phosphate dehydrogenase, this difference attained statistical significance. This may be related to the amount of glucose absorbed as such from the small intestine in animals on the different diets.