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

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.

Investigation of the Formal Pathogenesis of Green Liver Discoloration in Organically Reared Female Bronze Turkeys (Melleagris gallovapo)

“…The findings of the performed blood and liver analyses in this study give insight into the formal pathogenesis of green liver discoloration, suggesting a flock-specific subacute etiology at the age of 70 to 75 days and an individual, more acute etiology at the age of 120 to 127 days of fattening. This complements the findings concerning the causal pathogenesis of GL by Cuta et al [12] who presented a correlation of GL with the immunosuppressive hemorrhagic enteritis virus during the early fattening stage and joint or bone lesions or both in the late fattening stage. These results support the previously made assumption that a weakened immune system plays a bigger role in the development of GL than a single pathogen [11].…”

“…On the contrary, at days 70 to 75 of fattening, a more chronic inflammation process seems to take place in flocks affected by GL (high lymphocyte counts in individuals, high leucocyte numbers in affected flocks, and low ALB on both the flock and the individual level). These results complement the findings by Cuta et al [12] who found reduced body weights and a higher prevalence of inflammatory reaction within the livers of turkey hens with GL compared to turkeys without liver discoloration during both stages of the fattening period. A correlation was shown between GL at 70 to 75 days of fattening and the detection of hemorrhagic enteritis virus as an immunosuppressive agent as well as GL at 120 to 127 days of fattening and bone or joint lesions or both, suggesting 2 different pathogeneses of the disease [12].…”

“…These results complement the findings by Cuta et al [12] who found reduced body weights and a higher prevalence of inflammatory reaction within the livers of turkey hens with GL compared to turkeys without liver discoloration during both stages of the fattening period. A correlation was shown between GL at 70 to 75 days of fattening and the detection of hemorrhagic enteritis virus as an immunosuppressive agent as well as GL at 120 to 127 days of fattening and bone or joint lesions or both, suggesting 2 different pathogeneses of the disease [12]. Regarding liver enzymes, GLDH activity is considered the most specific parameter for damaged hepatocytes in birds [21,23].…”

“…A multifactorial process has been suggested, in which a weakened immune system plays a bigger role than the pathogenicity of certain agents [11]. In a recent study, significant correlations were found between GL and the detection of immunosuppressive turkey hemorrhagic enteritis virus in the early stage of the fattening period and joint/bone lesions in the late stage of the fattening period [12]. Two different pathogeneses of the development of GL were suspected [12].…”