Age-related histology of the bursa of Fabricius in bronze turkeys (Meleagris meleagris gallopavo)

The aim of the present study was to establish age-dependent histological changes occurring in the bursa of Fabricius of bronze turkeys. To this end, histological preparations from 60 clinically healthy birds (30 males and 30 females) were examined by light microscopy. The turkeys were divided into ten age groups – at 1, 7, 14, 28, 35, 49, 56, 90, 120 and 240 days of age. Specimens were processed by routine histological techniques. At one day of age, the wall of the bursa of Fab-ricius comprised 4 tissue layers: tunica mucosa, tela submucosa, tunica muscularis and tunica serosa, and the mucosa formed high fold directed to the lumen. These folds were filled with lym-phoid follicles, whose cortex and medulla were indistinguishable. From the 7th to the 120th days if age, the size of follicles increased and the peripherally located dark-staining cortex was clearly distinct from the centrally located lighter staining medulla. On the 240th day, signs of bursa of Fabricius’ involution were visible – destruction of follicles, cystic formations, thickening of inter-follicular connective tissue septa and fat accumulation within the wall. The obtained results al-lowed concluding that the physiological involution of the bursa of Fabricius started at the onset of sexual maturity.