Induction of tibial dyschondroplasia in turkeys by tetramethylthiuram disulfide (Thiram)

Tibial dyschondroplasia (TD) is a prevalent skeletal abnormality associated with rapid growth rate in many avian species; it causes enormous economic losses and is an animal welfare problem. Tibial dyschondroplasia is characterized by the presence of a nonvascularized, nonmineralized lesion that extends from the epiphyseal growth plate into the metaphysis of the proximal tibiotarsal bones. The mechanisms underlying TD development are not known, although they have been extensively studied in broilers using different induction models. However, an effective model for TD induction in turkeys has never been described. The objective of this study was to establish such a model by using tetramethylthiuram disulfide (thiram), an agent that is frequently used in broilers to induce TD. We found that dramatically longer exposures to much higher concentrations of thiram were required to induce TD in turkeys vs. broilers. In contrast to broilers, in which 50 mg/kg of thiram induces a high incidence of severe TD within 10 d, in turkeys, an exposure to 400 mg/kg of thiram for 11 wk was necessary for the development of severe TD lesions. These results show different mechanisms for TD induction in these 2 closely related species, suggesting differences in TD etiology between them.