Severe winter weather places stress on livestock herds that can dampen their immune response and lead to potential losses. South Dakota Cooperative Extension Veterinarian Russ Daly says the prolonged stress of weather events like the recent sub-zero temperatures and blizzards across the Midwest can cause problems that show up even after the weather improves.

“Wet, snowy weather combined with severe wind chills can produce stress that increases cortisol levels, which in turn dampen immune response,” Daly says. “This makes livestock, especially in young animals, more susceptible to a number of respiratory and digestive pathogens.”

There are some immediate dangers to the health of animals from severe cold, like chilling and frostbite, Daly said, but also problems that may not be apparent until seven to 14 days following the event.

Calf pneumonia due to respiratory pathogens like Mannheimia hemolytica, Pateurella multocida, and Haemophilus somnus usually shows up seven to 10 days following a stressful period or heavy pathogen exposure, according to Daly. “In young calves, scours organisms like rotavirus, coronavirus, and cryptosporidia are potential problems, and can manifest in a week or less,” he adds.

Heavy exposure to pathogens, such as when high numbers of animals are brought indoors, or when the stress is higher, can shorten incubation periods for these illnesses, Daly says. “In most cases, there’s little vaccination can do after the fact, so prompt identification of sick animals is essential,” says Daly. “Calves or lambs with respiratory infections often respond to antibiotic and other treatments that herd veterinarians would recommend.”

Daly said weather stress combines with other stresses animals may encounter, such as weaning, transporting, and processing. He suggests producers must consider winter conditions in light of management decisions. Anything that can be done to reduce weather stress to livestock should be considered carefully. “If processing or transporting, can be delayed until severe wind chills and wet, snowy conditions have subsided, they will reduce risks and losses.”

Daly said local veterinarians are the best sources for animal health information in adverse conditions. “No one else is more qualified to answer prevention and treatment questions in light of conditions on the ground in your area,” he suggests to producers.