Age-related Histological and Histochemical Changes of the Uropygial Gland in the Domestic Pigeon (<i>Columba livia</i>)

The present investigation aimed to analyze the uropygial gland's (UG) histological architecture and histochemical variation in the domestic pigeon at four posthatching age stages. The small and relatively undeveloped UG was observed at 1-day-old, and then the gland started to increase in size and complexity with age to reach its full functional size in the adult. The stroma became more organized with increased collagen fiber deposition, supporting the growing gland with age. The secretory tubules were more developed in the mature and adult pigeons than in other ages. The epithelial layer had four layers: basal layer, intermediate layer, secretory layer, and degenerative layer. The histochemical analysis using Mallory's trichrome stain revealed a positive reaction with all ages. The capsule, interlobular septum, papilla areas, and CT appeared blue, and the cellular components appeared red. The staining intensity increases with age till it becomes intensely blue with well-developed collagen in adults. Herbst corpuscles were encapsulated by a connective tissue sheath and comprised nerve cells arranged along the central axon, enveloped by collagen fibers. The findings from the current study may have a potential implication in poultry science and developmental biology.