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Changes in Hepatic Key Enzymes of Dairy Calves in Early Weaning Production Systems

S. Haga^*,1,2, S. Fujimoto, T. Yonezawa^*, K. Yoshioka^*, H. Shingu, Y. Kobayashi^*, T. Takahashi^*, Y. Otani^*, K. Katoh^* and Y. Obara^*

^* Department of Animal Physiology, Graduate School of Agricultural Science, Tohoku University, Amamiyamachi, Aoba-ku, Sendai 981-8555, Japan
National Livestock Breeding Center for Nagano, Arakoda, Saku, Nagano 385-0007, Japan
Department of Animal Production and Grasslands Farming, National Agricultural Research Center for Tohoku Region, Morioka, Iwate 020-0198, Japan

¹ Corresponding author: hagatiku{at}affrc.go.jp

The objective of the present study was to describe plasma hormonal and metabolite profile and mRNA expression levels and activities of the enzymes pyruvate carboxylase (PC), phosphoenolpyruvate carboxykinase (PEPCK), and acetyl-coenzyme A (CoA) carboxylase in the liver of male Holstein calves before (1 and 3 wk of age) and after (8, 13, and 19 wk of age) weaning at 6 wk of age. The mean plasma concentration of acetate and β-hydroxybutyrate increased, and that of plasma lactate and nonesterified fatty acids decreased with week, particularly after weaning. Plasma glucose concentration was lowest at 8 wk of age. The mean plasma concentration of insulin and glucagon did not change with time, and that of cortisol was greatest at 1 wk of age. In the liver, enzyme activity of PC was greatest at 1 wk of age and decreased with time. There was a significant relationship between the activity and the mRNA level for PC. Activity of PEPCK also decreased with week. Acetyl-CoA carboxylase activity tended to decrease with week, and activity at 13 wk of age was lower than that at other times. Expression of PC mRNA, but not that of PEPCK and acetyl-CoA carboxylase , decreased with week. We conclude that the hepatic gluconeogenic enzymes and acetyl-CoA carboxylase activities tend to decrease with age, reflecting changes in plasma metabolites in early weaning production systems.

Key Words: calf • early weaning • gluconeogenic enzyme • liver