By Rick Sibbel, DVM
Merck Animal Health was pleased to co-sponsor the 2014 BRD Symposium, which focused on new and improved strategies to prevent and control this costly disease. We will share some of the latest research findings and management techniques in this and upcoming blog posts. But, we also want to hear from you. If you attended the symposium, please share your thoughts, reactions and ideas. What information did you find most relevant? Have you changed your approach to addressing BRD?
Reducing stress in newly weaned calves is critical to ensuring a smooth transition into the feedlot and to protect them from health challenges. These young animals are vulnerable as they encounter numerous dramatic changes at a time when maternal immunity is on the decline. This creates a particularly easy pathway for BRD, which remains the primary cause of mortality in feedlot calves.
We know that calves entering the feedlot experience both psychological and physical stressors – such as maternal separation, transportation, social mixing, restraint and dietary changes. But, we know less about how individual stressors or combinations of stressors affect the calf’s immune response in the face of a respiratory challenge.
Philip Griebel, D.V.M., Ph.D., is a professor of immunology, School of Public Health, University of Saskatchewan, and he presented research results to expand on this further.
The study used a BRD challenge and analyzed the effects of specific stressors on clinical disease and immune response following bovine herpes virus (BHV-1/IBR) infection of naive calves. Crossbred calves were randomly sorted from a single herd into five groups. Transportation stress was compared to abrupt weaning plus transportation, or transportation following a two-step weaning process.
Body weight, rectal temperature and virus shedding in nasal secretions were monitored daily in all groups. These measures confirmed that calves, with or without stressors, developed clinical signs of an acute BHV-1 infection. All of the infected calves recorded significant declines in body weight during the first four days following infection and had similar increases in rectal temperatures. Neither transportation alone or transportation combined with weaning affected fever responses.
Transportation alone, but not when combined with abrupt weaning, increased BHV-1 shedding compared to calves that were pre-adapted to such stressors. There was no impact on duration of shedding. More study is needed to tell us whether transportation stress influences the severity of a BHV-1 infection.
The stressors imposed did have differential effects on innate immune responses. Of particular interest is that two-step weaning significantly reduced the pro-inflammatory response during BHV-1 infection.
In the end, the findings are consistent with previous studies that implicate weaning and transportation as stressors contributing to BRD severity and mortality but each stressor or combination of stressors can have different effects. This tells us that management strategies to minimize stress in weaned calves help support immune responses in the face of a respiratory challenge.
You can get more information on this research or order a copy of the 2014 BRD proceedings at http://brdsymposium.org/.