Investigating the Concentrations of Thyroid Hormones and Cortisol in Holstein Cows Before and After Parturition

Studying the changes in the concentration of cortisol and thyroid hormones in blood serum is considered an effective step in monitoring the health of animals. The purpose of this study was to investigate the concentration of thyroid hormones and cortisol in Holstein cows two weeks before and two weeks after calving. This research was a quasi-experimental study conducted on 60 three-year-old Holstein cows. Blood samples were taken from tail vein 14 days before birth and 14 days after birth. The concentration of thyroid hormones and cortisol were investigated using an ELISA kit. The levels of thyroid-stimulating hormone (TSH), thyroxine (T4 and T3), and cortisol were compared in three groups of heifers: one pregnant and two pregnant heifers. The level of T4 hormone after the birth of animals (7.07±3.26 ng/dL) was significantly higher than its level before this event (4.98±1.83 ng/dL) (P<0.05). However, T3 and TSH levels were not significantly different before and after parturition. It seems that the concentration of T4 before parturition is lower than the concentration of this hormone after parturition. The results of this research indicate that cortisol, T3, and TSH hormone levels before and after parturition are statistically the same. However, the concentration of thyroxine hormone two weeks after parturition was higher than it was two weeks before parturition