Concentration of cortisol, insulin, glucose and lipids in the blood of calves at various ages

Clinically healthy calves (n=30) of the Holstein-Friesian breed, at different ontogenic periods (15 days, 2 and 4 months of age), were investigated in this work. Blood samples were obtained by jugular venepuncture, always in the morning, 1 hour after feeding. The concentration of glucose was determined in the blood. Cortisol, insulin, lipids and cholesterol concentrations were determined in the blood sera. After statistical analysis of the obtained results, we found that the mean values for serum cortisol concentrations in calves at 15 days and 2 months of age were very similar. At 4 months of age, cortisol level was slightly lower, but the difference was not statistically significant. The mean values of insulin concentration was higher in calves at 2 months of age when forage and concentrated feed were offered besides milk, but in 4 months old calves the values were significantly lower (p<0.05). The mean blood glucose concentrations were similar and higher than the physiological values in calves at 15 days and 2 months of age, but values at 4 months of age were significantly lower (p<0.01). Rapid absorption of glucose in the calves' digestive system at 15 days and 2 months of age, contributed to the high level of glycaemia 1 hour after milk intake.