From Merck Animal Health's BRD Report: From the Fence PostThis post is part of a series that focuses on understanding antibiotic resistance, defining what antibiotic stewardship means and how cattle producers can be better stewards of antibiotic use. Brian Lubbers, D.V.M., Ph.D., Diplomate ACVCP, director of the Microbial Surveillance Lab, a unit of the Kansas State Veterinary Diagnostic Laboratory, is a contributor for this series.

We’ve talked in the BRD Report blog about the need to spread out the stressors associated with weaning. Pulling calves from their dam and shipping them to a feedyard, all within a very short time period, places them under tremendous stress and can seriously impair their ability to fight off disease.What happens when calves are put under such stress?

  1. Cortisol levels increase. Cortisol, which is naturally released under stressful conditions, suppresses the immune system.
  2. White blood cells decrease. High cortisol levels weaken white blood cells, which makes it harder for them to hunt down and kill viruses and bacteria.
  3. The mucosal barrier in the upper respiratory tract is disrupted. This means the protective barrier covering the upper respiratory tract is damaged, allowing viruses and bacteria to enter.

Studies have implicated weaning and transportation as key stressors contributing to BRD severity and mortality. Indeed, this cascade of events cripples calves’ immune systems and makes them more susceptible to infection. Plus, calves won’t respond well to vaccines if given during this stressful time.

Take the opportunity to be proactive by implementing a solid 45- to 60-day weaning program. These programs add value – $8-12/cwt – and are the right thing to do to keep calves healthy.