An Explorative Study of the Causal Pathogenesis of Green Liver Discoloration in Organically Reared Female Bronze Turkeys (Meleagris gallopavo) Considering the Infectious Risk Factors

SIMPLE SUMMARY: Organically raised turkeys investigated in a recent study showed a high prevalence of green liver discoloration. The condition is commonly associated with bone alterations and is potentially caused by opportunistic bacteria. This study was performed to determine possible infectious risk factors and reduce disease prevalence. The prevalence of green livers has decreased between both studies, and there was no explicable significant correlation with bacterial or parasitological findings. However, there was a significant correlation between green livers and the immunosuppressive turkey hemorrhagic enteritis virus at the early fattening stage. Hens with virus detection had impaired physical health. At the late fattening stage, there was a significant correlation between green livers and joint/bone lesions, as described in previous literature. It can be assumed that the hemorrhagic enteritis virus affects the pathogenesis of green liver discoloration at the early fattening stage. Therefore, an adequate vaccination schedule should be implemented in poultry farms to reduce the prevalence of discoloration and improve animal health. However, further standardized investigations to determine and evaluate possible infectious risks regarding green liver discoloration are necessary. ABSTRACT: A recent study revealed that organically raised Bronze turkeys showed a high prevalence of green liver discoloration. This alteration is commonly associated with the Turkey Osteomyelitis Complex and potentially caused by opportunistic bacteria. Therefore, 360 organically fattened Bronze turkeys were examined post-mortem throughout two fattening trials with two examinations each to determine possible infectious risk factors and reduce disease prevalence. Clinical and pathoanatomical examinations were performed on every hen. Histopathological, bacteriological, parasitological, and virological examinations were performed on at least six hens without and, if applicable, six hens with green livers on each examination date. Overall, 9.0% of all hens had a green liver without a correlation with bacterial or parasitological findings but multiple health impairments. The discoloration correlated significantly with the detection of immunosuppressive turkey hemorrhagic enteritis virus at the early stage and macro- and histological joint/bone lesions at the late fattening stage, indicating the presence of two different predisposing pathogeneses. Flocks not being vaccinated against hemorrhagic enteritis but having a virus-positive sample showed the highest prevalence of green liver discoloration and developed worse in various parameters. In conclusion, an adequate vaccination schedule and the prevention of field infections may lead to a decreased risk of performance reduction and improved animal health.