This weekend’s blizzard in western South Dakota created deadly conditions for cattle in affected areas. Reports of cow and calf death losses, along with displacements of herds due to drifting over of fencelines are still coming in. These are issues that ranchers are dealing with presently.
After mortalities are disposed of and the lost cattle returned to pastures, ranchers may still face problems with their animals in the days and weeks following the storm.
Prolonged stress placed on animals, especially younger animals, due to weather events results in increased cortisol levels in the animals’ bloodstream, which can have profound effects on the immune system. Prolonged stressful events, such as the blizzard experienced over the weekend, are more significant than short-term events.
- Long-term stress can have the effect of shifting the immune system towards production of antibodies and away from cell-mediated responses. In practical terms, this means that the body has less of an ability to respond to diseases caused by viruses. In growing cattle, respiratory diseases are often caused or started by Infectious Bovine Rhinotracheitis (IBR, or “red-nose”), Bovine Respiratory Syncytial Virus (BRSV), and Bovine Viral Diarrhea Virus (BVDV).
- Respiratory diseases in cattle generally have an “incubation period” of 7-14 days. Therefore, ranchers might expect that cattle affected by the blizzard could break with these illnesses over the next two weeks.
Weaned calves may be more susceptible to coccidiosis as well. This condition will present as bloody stools, along with dehydration and depression in more severely affected calves. Prompt identification of affected calves and treatment with individual or feed-based medications is important.
- Ranchers should consult with their veterinarian whether feed- or water-grade antibiotics, especially in weaned calves, would be appropriate for any of these conditions.
In spring calving herds, the storm hit in the midst of ranchers’ normal preparations for weaning. Herds were in various stages of the process, anywhere from having calves weaned already to calves having their first pre-weaning vaccination, to calves that had not had pre-weaning vaccinations at all.
Long-term stress has the effect of inhibiting the immune system against infectious diseases, but it also inhibits the body’s response to vaccines.
- Ranchers should give the calves and their immune systems 7-14 days following the blizzard event to recover from the stress before giving initial or booster doses of vaccines. Vaccinations will be less effective in cattle that are still under the influence of cortisol due to stress.
- Long-term stress has the effect of inhibiting the immune system against infectious diseases, but it also inhibits the body’s response to vaccines.
In cattle, it is generally considered that the effect of stresses on the body are additive. This means that any sort of transportation, processing, or weaning will add to the stresses already encountered by cows and calves going through the blizzard, or faced with moving through snowbanks or muddy lots.
- Likewise, ranchers should hold off on any processing, weaning, or long-distance transporting of cattle for 7-14 days following the weather event.
- The best source of information regarding animal health in adverse conditions is the local veterinarian. There is no one more qualified to offer advice for prevention and treatment in light of local conditions.
The blizzard also coincides with the traditional marketing window for spring calves. If at all possible, ranchers should consider delaying marketing until the calves have had time to recover from the added stress load.
- Feedlots or backgrounders who purchase calves who have undergone these conditions should do all they can to minimize stress and provide as much TLC as possible. Feeders should consult with their veterinarian concerning timing of arrival vaccinations and possible preventative strategies.