Archives of Current Research International

The bursa of Fabricius (BF) is the primary lymphoid organ unique to birds and is central to the ontogeny of humoral immunity. The present study was undertaken to compare the age-related gross, biometrical, histological and histochemical architecture of the BF between an indigenous breed, Haringhata Black chicken, and a commercial broiler chicken, from day-old to day 60 of post-hatch life. Fifteen birds of each breed were divided into five age groups (day 0, 15, 30, 45 and 60). Grossly, the bursa was an oval, chestnut-sized, creamy-white to pale-yellow sac attached by a short stalk to the dorsal wall of the proctodeum in both breeds. Organ weight, length, width and thickness increased progressively, peaking around days 30–45, and declined by day 60. Histologically, the bursal wall showed a tunica mucosa thrown into plicae lined by pseudostratified ciliated columnar follicle-associated and interfollicular epithelia, a lymphoid-follicle-rich lamina propria, tunica muscularis and tunica serosa in both breeds at all ages, with breed-specific differences in plical height, follicular dimensions and epithelial height. The histoarchitecture, including the presence of a more organised cortex, a more cellular medulla, distinct nuclear morphology, abundant connective tissue, greater vascularity and a gradual pace of bursal growth, was observed in Haringhata birds. The epithelial height was greater in Haringhata birds than in broiler birds in all age groups. Histochemical staining revealed neutral and acidic mucosubstances (PAS and Alcian blue positivity) that varied in intensity with age. Collagen fibres increased, whereas elastic fibres decreased progressively with age in both breeds. These findings establish comparative baseline morphometric data on bursal ontogeny in an indigenous and a commercial chicken breed that may assist in correlating structural maturation with age-related immunocompetence.