Submitted to: Western Poultry Disease Conference
Publication Type: Proceedings
Publication Acceptance Date: April 24, 1999
Publication Date: N/A
Interpretive Summary: Turkey osteomyelitis complex (TOC) is a turkey disease which results in bone, joint, and muscle infections in processed turkey carcasses. In a series of four experiments, it is shown that treatment of turkeys with a compound (DEX) known to mimic the physical changes caused by stress, can cause turkeys to develop TOC whether or not they are challenged with bacteria. High levels of stress can cause the immune system to function improperly. These turkeys then become infected by breathing air containing bacteria normally present in the environment. The effects of experimental DEX treatment appear to be much more severe in older birds, which is important because TOC also becomes a problem as the bird matures. The ability to produce TOC using this compound is important, as it enables researchers to test substances that may protect birds from the disease, and may also enable the genetic selection of turkeys which are better able to withstand the stresses of intensive turkey production.
Technical Abstract: We have demonstrated that the synthetic glucocorticoid, dexamethasone (DEX), when inoculated into the thigh muscle of turkeys at a dosage of 2mg/kg, will induce all of the lesions of turkey osteomyelitis complex (TOC), including green liver, arthritis/synovitis/tendonitis, and muscle and bone lesions. In expt.1, DEX treatment alone produced 8% TOC incidence in 5-week-old birds. In expt. 2, birds which survived experiment 1 were treated with a second series of DEX injections at 13 weeks of age, resulting in multiple TOC lesions in 60% of the birds and green liver in 44%. In expt.3 birds were treated with DEX at 5 weeks of age and challenged with air sac inoculation of E. coli. Survivors were again treated with DEX at 13 weeks of age. The two DEX treatments resulted in 64% TOC and 64% green liver in birds never challenged with E.coli. In expt. 4, birds were treated with DEX at 2, 5, and 10 weeks of age. The incidence of TOC increased after the second and third DEX treatments, resulting in 67% TOC and 35% green liver. Seven healthy control birds from experiment 4 were treated with a single series of DEX injections at 12 weeks of age. Green liver was present in 2/7 and TOC lesions in 6/7 of these birds within 9 days post treatment. These results indicate that treatment of turkeys with 2mg/kg DEX induces the development of TOC in older birds, and suggests that immunosuppression due to a high stress response may be involved in the etiology of TOC. Treatment with DEX is being used to test nutritional and physiological immunomodulators, and may be useful in the genetic selection of turkeys with a lower stress response and better disease resistance.