Postnatal Gross Morphological and Histoenzymic Studies on the Thyroid Gland of Assam Goat

The thyroid gland was composed of right and left lateral lobes connected by a narrow isthmus. The location of the isthmus over the trachea varied in male goats which ranged from 4th to 9th tracheal rings. Various biometrical parameters viz. length, width, thickness and weight of the thyroid gland showed a highly significant (P<0.01) increase between various age groups as well as between the thyroids of right and left sides of the body in Assam goats. Accessory thyroid tissue was not observed in any of the male goats. Different biometrical parameters of the isthmus showed an increasing trend with the advancement of age and the variations were found to be highly significant (P<0.01) between various age groups, except in respect of their weight. The activity of LDH in the follicular epithelium of the thyroid gland varied from weak to intense from 4 to 10 months of age (groupsIII to VI). However, MDH showed a strong activity in these cells at birth (group-I), which was reduced to moderate in 4 month old kids (group-III) and again elevated in older goats. The enzymic activity of G-6-PDH was variable from mild to moderate in the male goats. The intertubular stroma of the thyroid gland showed no activity for MDH and G-6-PDH in all the age groups. But a mild activity of LDH enzyme was seen in goats from 6 month of age (group-IV) onwards.