Cold weather is not just hard on the people taking care of animals, it can be tough on the animals themselves, said Russ Daly, Professor, SDSU Extension Veterinarian, State Public Health Veterinarian.
"It's not just our imagination that cold temperatures often bring with them an increase in sick calves; there are physiologic reasons why cold weather increases the risk of respiratory disease such as pneumonia in dairy calves," Daly said.
He explained that cold weather enhances the growth of certain respiratory germs inside a calf's nose and upper respiratory tract. "The more bacteria present in the upper respiratory tract, the more likely they'll reach the lower lung and cause pneumonia," he said.
Daly added that cold weather also thickens up mucus and impairs the work of the ciliary escalator - the fine hair-like cell structures that sweep bacteria and foreign material from the lower airways up to the throat to be coughed up.
"All these factors increase the risk of pneumonia in calves," he said.
Detection and Prevention
Proper ventilation providing fresh air to calf barns is important to preventing respiratory diseases - a goal that can conflict with efforts to protect calves from cold temperatures.
To ensure calves are equipped to deal with cold temperatures, along with fresh air, provide deep dry bedding and adequate nutrition.
Early detection is key
Because of the increased risk of respiratory disease following cold weather, caretakers need to focus even more of their energy on the calves' health.
"Early detection and treatment is important to the calf's immediate health as well as to her long-term production," Daly said.
He pointed to evidence which suggests dairy cows who were treated more than once for respiratory disease as calves produce 10 percent less milk in their first lactation, and 15 percent in their second lactation.
"These effects on milk production have not been demonstrated in calves only treated once, underlining the importance of effective and timely treatment," he said.
Heifers that suffered pneumonia as calves are older on average at first calving compared to heifers that did not get sick.
Antibiotic Treatments
When prevention efforts fail, Daly said early detection and effective treatment of respiratory disease can improve the odds of a calf surviving respiratory disease as well as their productivity as a cow.
"Work with your veterinarian to improve these aspects of your operation, and pay close attention to calves when cold winter temperatures set in," he said.
Many drugs - available by prescription through veterinarians -have demonstrated effectiveness against respiratory pathogens. Antibiotics labeled for use against Mannheimia, Histophilus and Pasteurella are the most effective in treating calf respiratory disease.
"As there is not a single drug that has proven effective in every situation, antibiotic choice should be guided by veterinary consultation and, if available, bacterial culture and antibiotic sensitivity results from previous calves," Daly said.
Using nasal swabs to identify pathogens and guide treatment should be approached with caution, but may provide important information in some cases.
Lung cultures from calves that died of pneumonia may be more useful, but Daly said their representativeness for future calf groups should be considered carefully.
"Pneumonia and other infections caused by Mycoplasma bovis are particularly difficult to treat. Antibiotics labeled for Mycoplasma should be utilized and treatment length may need to be prolonged," he said.
Identifying Mycoplasma through lab testing is a valuable piece of information that can help with treatment and prognosis.
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