Age-related changes in the incidence of tibial dyschondroplasia in turkeys.

Age-related changes in the incidence and severity of tibial dyschondroplasia (TD) and its relationship to body weight and other bone pathologies were studied in turkeys from ages 2 through 15 wk. A steady increase in the incidence and severity of TD was observed from 11 wk onwards. Whereas there was no correlation between the body weight and TD in early ages, during Weeks 14 and 15 the turkeys with severe TD had significantly higher body weight relative to those without or with mild lesions. Starting from Week 13, hemorrhage was evident in the base of TD-affected growth plates of many turkeys, which increased linearly during the following weeks. Histological examination of these areas revealed mild necrosis with erosion in TD tissues accompanied by occasional bone formations, fibrosis, and the presence of multinucleate chondroclasts and large number of erythrocytes adjacent to lesions. Sporadic rod-like bacterial colonies were discernible in TD tissues and cartilage canals. These studies show 1) whereas the onset of TD may have an independent etiology, the severity of the disease may be influenced by a higher body weight; and 2) subepiphyseal hemorrhages possibly facilitate a healing-type response that leads to replacement of TD tissue by way of resorption, bone formation, and fibrosis, but simultaneously makes the tissue accessible to bacteria.