Abstract
The studies were carried out on cows of Holstein black-and-white breed. 2 groups of 10 heads each were formed. The milk yield for lactation was 10 thousand kg in the first group, and - 5 thousand kg in the second group. Blood was collected from the subcaudal vein monthly during lactation. T3 and T4 were determined in the blood serum. The functional “load” on the thyroid gland was performed at the peak of lactation (3 months) and at its end - at 9 months. The TSH preparation at a dose of 0.5 u/kg of live weight was administered intramuscularly on an empty stomach before morning feeding. T3 and T4 hormones in the blood were determined before the injection of TSH and 0.5 one and two hours after the injection. Kath was calculated using the formula Т1 – Т0 / Т0 where Kath is the coefficient of activity of thyroid hormones. T0 – T3 and T4 levels before TSH injection T1 – T3 and T4 levels 2 hours after TSH injection. During lactation, the level of milk production and thyroid hormones varies inversely with the average daily milk yield. During the period of high milk productivity (2,3,4 months of lactation), the concentration of T3 and T4 in both groups was low, and later increased and was maximum in the 8th month of lactation. The functional reserves of the thyroid gland in high-yielding cows in 3 and 9 months of lactation are lower in relation to low-yielding cows.
Highlights
The main reserve for increasing the level of livestock productivity is the realization of its genetic potential, taking into account the physiological and biochemical characteristics of their body [1-3]
To identify the functional reserves of the thyroid gland in experimental endocrinology, the thyroid-stimulating hormone thyroidstimulating hormone (TSH) is used
To determine the functional reserves of the thyroid function of the thyroid gland in productive cows by the method of functional "load" with the help of thyroidstimulating hormone
Summary
The main reserve for increasing the level of livestock productivity is the realization of its genetic potential, taking into account the physiological and biochemical characteristics of their body [1-3]. The study of individual characteristics of animals will allow to select purposefully animals with a high genetic potential of their productivity. In this regard, special attention should be paid to the study of the hormonal status that allows to study the productivity formation. The study of the thyroid gland state, the functioning of which is directly related to the formation of animal productivity, is of particular interest. The functional "load" with thyroid-stimulating hormone allows to set the functioning limits of the thyroid gland [13] In this regard, the knowledge of the functional reserves of the thyroid gland in cattle will allow to use the data obtained in breeding work with cattle. To determine the functional reserves of the thyroid function of the thyroid gland in productive cows by the method of functional "load" with the help of thyroidstimulating hormone
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