Year in and year out, lameness is one of the leading causes of mortality in broilers, making the condition a significant economic concern for the poultry industry. But because the incidence rate of lameness is low in research flocks, the phenomenon has been difficult to study, which has hampered efforts to develop measures that may help producers.
However, a team led by researchers at the University of Arkansas has developed a wire-flooring model that reliably induces lameness in broilers at levels sufficient to allow in-depth study of the condition. The team published the results of their study in the April issue of Poultry Science, a journal published by the Poultry Science Association (PSA).
Yielded significant results
The model has already yielded significant results, including the finding that lameness in broilers due to the most common cause of the condition, bacterial chondronecrosis with osteomyelitis (BCO), may be reduced by administering probiotics prophylactically from the first day of rearing. Hence, probiotics may lessen or even eliminate the need for antibiotic treatment of BCO-related disease conditions in growing broilers.
“One way the BCO bacterium spreads is by entering the bloodstream via translocation from the gastrointestinal tract,” said Dr. Bob Wideman, lead author and professor in the Department of Poultry Science at the University of Arkansas. “Once in the bloodstream, some of the bacteria find their way to the growth plates of growing bones, where they are harbored in microfractures. The bird’s immune system can’t reach them there, and they grow rapidly and begin destroying bone minerals. This occurs primarily in the hip joint or proximal femur, and in the proximal tibia. It’s the damage caused by the festering of BCO bacteria that leads, first to subclinical lesions, and ultimately, if unchecked, to lameness.”
Dr. Wideman’s team speculates that probiotics help reduce BCO-induced lameness by lessening bacterial translocation from the gut, which helps prevent BCO transmission. Specifically, according to the article, “probiotics may interfere with the development of osteomyelitis by attenuating intestinal populations of pathogenic bacteria, improving gut health to reduce bacterial leakage (translocation) across the gut wall, or by priming the immune system to better eliminate translocated bacteria.”
Reduced incidence of lameness for broilers
Over the course of five experiments conducted from December 2009 to April 2011, the researchers found that adding probiotics to the birds’ diets beginning at one day of age consistently reduced the incidence of lameness for broilers reared on wire flooring.
The experimenters were able to begin an effective investigation of BCO-induced lameness by developing a wire-flooring model that consistently induced the condition in research flocks at rates high enough to enable statistically sound study. The wire flooring model works by dependably imposing greater torque and shear stress on susceptible leg joints, which, the authors suggest, results in microtrauma to bone growth plates, creating the microfractures conducive to BCO described above.
Animal procedures for the five experiments conducted by the research team were approved by the University of Arkansas Institutional Animal Care and Use Committee.
“We feel confident that this new model will allow researchers, for the first time, to more deeply investigate the etiology, pathogenesis, and treatment strategies for BCO,” said Dr. Wideman. “This should lead to more effective preventive strategies applicable to commercial flocks, which in turn will help decrease economic losses due to BCO.”
Previously, pathogenic bacteria had to be injected intravenously into broilers and turkeys to induce lameness for study purposes. The new experimental model instead provides, according to the article, a safer mechanism for studying the condition by “reliably triggering BCO in commercial broilers without purposefully exposing the flock to known pathogens.”
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