Bu çalışmada, erken embriyonal dönemde yumurtaya verilen teslosleron propiyonalın fTP), tavuklarda bursa Fabricii'nin embriyonal gelişimi üzerindeki elkileri ile kuluçkadan çıkıştan sonra bu organda oluşan histolojik de­ğişikliklerin incelenmesi amaçlanmıştır_ Çalışmada B55 yerli hibrit anaçlardan elde edilen 350 adet dOllü yumurta kul­lanıldı. Bu yumurtaların yarısı kontrol grubu olarak kullanllır1

The aım of this study was to investigate the effects ol in ovo administrated testosterone propionate (TP) on the embryonıc development ol bursa ol Fabricius and also to determine the histological changes occuring at post­hathcing period. In the study, toıally 350 lertilized eggs ol a hybrid breed, B55 were usecl. The eggs were divided into two groups. First-group eggs were served as controls, in the second group-eggs, which were treated with tesıosterone propionate, constituted experimentals. light microscopic observations have showed that in ovo hormonal bursectomy adversely allected Iymphoid follicle development via blocking the epithelial bud formation. Nevertheless, TP-treatment did noı compleıely prevented folliele formation in the organ; atrophic and degenerated lollicles wilh cysts were also seen, a/lhough they were in smail numbers. In TP-trealed group, the organ was smailer than those of conlrols and most ol the Iymphoid follicles have nol compleled their development. At the lirst week of post·halching period Iympho­id inliltration areas and cysts were obseNed in the lamina propria ol the organ. At the 8th week ol post-hatching pe­riod, a rudiment of the organ which was mainly constituted of the connective tissue conıaining diffuse Iymphoid in­fillration areas was observed