Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 29, 2000
Publication Date: N/A
Interpretive Summary: Turkey osteomyelitis complex (TOC) is a turkey disease which results in bone, joint, and muscle infections. Because many different opportunistic bacteria have been isolated from the infections, we believe that turkeys which get this condition are unable to fight infection. We have shown that the immune system of turkeys with TOC is different from that of normal turkeys and that these changes may result from the selection of turkeys with faster growth rates. We have been able to reproduce all of the types of infection that occur in TOC by treatment of turkeys with a compound known to mimic the physical changes caused by stress. These studies suggest that decreasing the level of stress experienced by the birds may also decrease infection. We were able to decrease the level of disease and increase body weight by giving the turkeys extra vitamin D in their drinking water. Differences in the ability to utilize vitamin D may be important in general disease resistance and may also enable the genetic selection of turkeys which are better able to withstand the stresses of intensive turkey production.
Technical Abstract: Turkey osteomyelitis complex (TOC) is defined by the U. S. Food Safety Inspection Service (FSIS) to include normal-appearing processed turkey carcasses which contain lesions including green discoloration of the liver, arthritis/synovitis, soft-tissue abscesses, and osteomyelitis of the proximal tibia. The lesions are associated with many different opportunistic organisms, mainly Staphylococcus aureus and Escherichia coli suggesting that TOC incidence may be influenced more by deficiencies in the host immune response rather than by the virulence of any one organism. This syndrome is primarily a disease of adolescent male turkeys and birds with TOC lesions have been shown to have decreased indices of cell-mediated immunity, leading to the hypothesis that defects in the immune response of individuals within flocks of male turkeys may be responsible for the occurrence of these opportunistic infections. We have developed an experimental model for this disease in which treatment with dexamethasone (DEX), either with or without air sac inoculation with Escherichia coli, produces all of the lesions associated with TOC. These studies suggest that TOC is a result of stress-induced immunosuppression in a sub-population of male turkeys which respond to the stressors of modern poultry production in a detrimental manner. Supplemental vitamin D3 treatment protected male turkeys from the immunosuppression induced by multiple treatments with DEX, and resulted in decreased incidence of mortality, TOC, green liver, and isolation of bacteria from tissues, lower air sacculitis scores, and lower heterophil to lymphocyte ratios than non-supplemented controls. Vitamin D3 also protected body weight, relative weights of the liver, heart, spleen, and bursa, and clinical chemistry values from the effects of DEX treatment.