AGE-RELATED-CHANGES IN THE INCIDENCE OF TIBIAL DYSCHONDROPLASIA IN TURKEYS

Age-related changes in the incidence and severity of tibial dyschondro plasia (TD) and its relationship to body weight and other bone patholo gies were studied in turkeys from ages 2 through 15 wk. A steady incre ase iri the incidence and severity of TD was observed from 11 wk onwar ds. 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 sig nificantly higher body weight relative to those without or with mild l esions. Starting from Week 13, hemorrhage was evident in the base of T D-affected growth plates of many turkeys, which increased linearly dur ing the following weeks. Histological examination of these areas revea led mild necrosis with erosion in TD tissues accompanied by occasional bone formations, fibrosis, and the presence of multinucleate chondroc lasts and large number of erythrocytes adjacent to lesions. Sporadic r od-like bacterial colonies were discernible in TD tissues and cartilag e canals. These studies show 1) whereas the onset of TD may have an in dependent etiology, the severity of the disease may be influenced by a higher body weight, and 2) subepiphyseal hemorrhages possibly facilit ate a healing-type response that leads to replacement of TD tissue by way of resorption, bone formation, and fibrosis, but simultaneously ma kes the tissue accessible to bacteria.