Dynamics of thyroid hormones in Stavropol breed sheep in postnatal ontogenesis

Abstract

Abstract The aim of the research was to study the dynamics of thyroid hormones and thyroid-stimulating hormone of the pituitary gland in Stavropol breed sheep in postnatal ontogenesis and the establishment of thyroid status in animals before insemination, during pregnancy and after childbirth. Determination of concentration of total triiodothyronine, free thyroxine and thyroid stimulating hormone in serum was performed by solid-phase enzyme immunoassay (ELISA) using standard test systems. As a result of the studies, the level of thyroid hormones and thyroid-stimulating hormone in the blood of sheep of Stavropol breed in postnatal ontogenesis was determined. It was established that at the birth of lambs, the lowest level of triiodothyronine (2.55 ± 0.04 nmol/l), thyroxine (19.47 ± 0.45 pmol/l) and thyrotropic (0.31 ± 0.05 Mme/ml) hormone was observed in the blood, compared with other age periods. By the age of three months, the levels of triiodothyronine and thyroxine increased significantly by 7.7% and 24.8%, respectively. When comparing the data in six monthly young ewes, the concentration of all studied hormones was the highest in comparison with other age groups (triiodothyronine – 3.11 ± 0.21 nmol/l; thyroxine – 26.29 ± 0.97 pmol/l; thyrotropic hormone – 0.81 ± 0.09 Mme/ml). In the age of nine months, a significant decrease in triiodothyronine by 16.8%, thyroxine - by 13.2% and thyroid-stimulating hormone - by 34.6% was observed, compared with ewes of 6 month old. By the age of 12 months, only free thyroxine was significantly changed, its serum concentration increased by 9.5% and amounted to 25.21 ± 0.31 pmol/l, compared with the data of nine-month-old sheep. It was found that the concentration of triiodothyronine changes significantly in sheep after childbirth and is 2.53 ± 0.03 nmol/l, which is 6.3% more than in pregnant ewes. The level of thyroxine on the 90th day of pregnancy decreases by 5.3%, and by the 135th day by 16%, compared with the previous period of the study. Thyroid-stimulating hormone in the blood serum of sheep on the 90th day of pregnancy becomes significantly lower by 29% (p ⩽ 0.05) than its concentration in non-pregnant ones. After childbirth, thyroid-stimulating hormone significantly increased by 26.66% (p ⩽ 0.05). As a result of the studies, in sheep of Stavropol breed, standard sizes of the level of thyroid gland hormones (triiodothyronine, thyroxine) and thyroid-stimulating hormone were established.