Non-protein nitrogen supplementation increases gluconeogenic capacity in sheep

The effect of non-protein nitrogen (NPN) supplementation on the gluconeogenic capacity of sheep was investigated. Three groups of six sheep each, control, moderate (MN=0.55 g N/kg0.75/d) and high (HN=1.28 g N/kg0.75/d) NPN were used. A propionate loading test (PLT) was performed in each animal after 7 or 15 days of NPN supplementation by infusing a bolus of sodium propionate, and plasma glucose, urea, lactate and insulin concentrations were measured up to 88 min after infusion. Liver glycogen concentration and the activity of gluconeogenic enzymes and complementary ureagenic enzymes were determined at 9 or 17 days of the supplementation period. Glycemia and lactacidemia increased during the PLT in all groups, being highest in HN sheep. Liver activity of PEPCK was higher in HN than in the control sheep. NPN supplementation in sheep increased plasma urea and lactate concentrations and liver PEPCK activity associated to an increased gluconeogenic capacity from propionate or lower peripheral glucose utilization.