The study measured several indications of healthy calves’ immune-system response to being continuously exposed to a PI calf—just as they would be if penned with one in a feedlot. The resulting repeated immune stimulation increased several indicators of immune-system response and the inflammation that often kills BRD-infected calves, including levels of the signaling proteins interferon, interleukin and tumor necrosis factor.
The researchers suggest this increased action of the immune system in the presence of PI BVD helps explain why one of their earlier studies found the presence of the virus in a pen of calves slows down their growth. BVD could be acting on either directly on the tissues or indirectly through the endocrine system, they believe. The good news? The single-source calves that had been preconditioned, including two months post-weaning introduction to feed at the ranch, vaccination with a respiratory virus vaccine including a bacterial pneumonia component and a clostridial, and deworming, were significantly less likely to show the telltale signs of immune-system damage, even when they found their way into a pen containing PI-BVD calves.
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