The keel bone in laying hens is prone to fractures, especially on the caudal third of the keel, which is also the last part to ossify. Keel bone fractures (KBF) typically occur between 25 and 50 weeks
Type 1 PRCC was characterized by papillae covered by cells with scanty cytoplasms which were arranged in a single layer on the papillary basement membrane, while Type 2 PRCC was characterized by cells
