Metabolism and Hormonal Status during the First Trimester of Lactation of First-Calf Cows with Long Barrenness
The aim of the work was to study the metabolic and hormonal profiles in first-calf cows with different reproductive abilities when restoring the sexual cycle. Twenty-four cows of Black-and-White Holstein breed were the objects of the investigation. The examination of the functional state of the cow reproductive system and blood sampling for analysis were carried out in 45-90 days after calving. Animals restored the sexual cycle and without gynecological diseases were selected for the experiments. In 11 months after calving, the animals were divided into two groups according to their reproductive state: pregnant cows (group I, n = 18) and barren cows (group II, n = 6). The biochemical status of group II cows was characterized by the reduced 1.5 times content of urea (p is less 0.05), the reduced 1.2 times activity of aspartate aminotransferase (p is less 0.05), and the increased 1.4 times activity of alkaline phosphatases (p is less 0.05) in the blood as compared to group I cows. A 3-fold decline in the circulating level of progesterone was observed in cows with a low reproductive ability. At the same time, concentrations of thyroid hormones, cortisol, and oestradiol-17beta in blood were similar in animals of both groups. Concurrently, many relationships between indicators of the state of the thyroid system and blood biochemical parameters in cows with different reproductive abilities differed significantly. Thus, in the group I, the blood concentration of phosphorus negatively correlated with the content of thyroxine (r = -0.521, p is less 0.05), whereas a positive interrelation between the values of these indicators was found in the group II (r = 0.872, p is less 0.05). At the end of early lactation, a positive correlation between alanine aminotransferase activity and the concentration of free triiodothyronine in the blood was typical for pregnant individuals (r = 0.530, p is less 0.05), but it was not observed in the group of barren animals. So, metabolism and the hormonal status, as well as their interrelation in first-calf cows with long barrenness when restoring the sexual cycle, have a number of features, which negatively affect the conception rate or preservation of early pregnancy.