Dynamics of morphometric indicators of the thyroid sheep in postnatal ontogenesis

Abstract

 The aim of the research was to study the dynamics of the morphometric parameters of the thyroid gland of sheep in postnatal ontogenesis. The  studies were carried out in the Stavropol Territory. The object of the study was the thyroid gland of sheep of the Stavropol breed at the age of 1 day  (newborns), 3, 6, 9 and 12 months. All animals were females, three in each  group. As a result of studies, it was found that the area of the thyroid follicle in sheep of the Stavropol breed increases to six months, and then decreases to nine months. The maximum average value is observed at six months (2233.00 ± 502.30 µm2),  the minimum average value was observed in newborns (802.50 ± 72.88 µm2). The area of thyrocytes decreased with age, reaching a minimum mean value (19.75 ± 0.27 µm2) at six months. After the age of six months, this indicator increases. The maximum average value is observed in newborn sheep. The dynamics of the area of the thyrocyte nucleus is similar to the changes in the area of the thyroid follicles. At six months, the maximum average value (24.95 ± 0.86 µm2) of this indicator is observed, and by nine months it decreases, reaching a minimum at 12 months (18.07 ± 0.47 µm2). The nuclear-cytoplasmic ratio of the thyroid thyrocyte in sheep has similar changes in postnatal  ontogenesis. From birth to six months, there is an increase in the average value  of  the nuclear-cytoplasmic ratio and the achievement of a maximum (0.47 ± 0.008 ed). However, by the age of nine months, the indicator declines in sheep. At 12 months, the nuclear-cytoplasmic ratio becomes equal to that of newborn animals (0.36 ± 0.008 ed).