Changes in selected biochemical blood parameters in dairy cows after administration of melatonin

In order to investigate the effect of melatonin on indexes of blood carbohydrate-lipid processes, cows were given melatonin intravenously in the amount of 0.1 mg/kg body weight in the morning on the second day after calving. Blood samples were collected three times: before, 1 h and 4 h after injection. The administration of the pineal gland hormone resulted in a significant (35%) increase in blood serum triglyceride (TG) concentrations and a nonsignificant (14%) increase in cholesterol concentration. At the same time in the experimental group, a lower free fatty acid (FFAs) concentration (by 13%) was observed along with lower values of FFA:TG and FFA: cholesterol ratios, while alanine aminotransferase (ALT) activity increased. The differences found in comparison with the control group were not significant. The glucose concentration and aspartate transferase (AST) activity did not change.