Hormonal and metabolic adaptations to periparturient and early lactation periods in dairy cows

The objective of the study was to analyze the blood plasma concentrations of insulin, thyroid hormones (T-3, T-4), glucose, free fatty acids (FFA), ketone bodies and basic haematological parameters for 8 weeks before calving and 12 weeks after parturition in 65 multiparous dairy cows of Black and White breed with high incidence of ketosis. The highest levels of blood plasma T-3, T-4, insulin and glucose were observed in the two last months of gestation. These hormones and glucose levels decreased significantly before parturition and in the first week after calving and remained at approximately the same level during the following 12 weeks. The lowest levels of blood plasma insulin and thyroid hormones were accompanied by the highest FFA content and the highest ketone body level after parturition. Haematological parameters analyzed here (Hb, Ht, RBC, WBC, 2,3-DPG) showed a tendency to be lower after calving, except for 2.3-DPG in the red blood cells, in comparison with values obtained during two months before parturition. The obtained results indicate the involvement not only of insulin in the dairy cows but of thyroid hormones in the mechanisms of homeorhesis during pregnancy as well as in lactation.