Comparative anatomical, histological and morphometric study of the thyroid gland in Egyptian Mulard duck (Cairina moschata × Anas platyrhynchos) and Egyptian turkeys (Meleagris gallopavo)

The thyroid gland of the mulard duck and turkey is a bilateral endocrine organ that is located in the thorax. The current study aimed to describe the topographical, anatomical and histological picture of the thyroid gland in ducks and turkeys. Eeighteen healthy adult males of ducks and Egyptian turkeys were selected. Gross morphology and histological analysis of thyroid tissue was performed. Grossly, thyroid glands appeared dark red oval bodies near the carotid artery. Histologically, glands contained thousands of follicles within a collagenous capsule. Follicle shapes ranged from spherical to elliptical. In ducks, follicular epithelium was squamous to cuboidal. In turkeys, epithelium was cuboidal to columnar based on activity. Colloid stained strongly positive in duck follicles but moderately to weakly in turkeys on PAS reaction. Connective tissue and follicular lining showed weak PAS positivity in both species. This study characterized thyroid gland location, gross anatomy and microscopic features in ducks and turkeys. Histological analysis revealed inter-species similarities and differences at the tissue and cellular level.