There is a reason cold weather brings on an increase in respiratory symptoms and pneumonia in calves, according to Dr. Russ Daly from South Dakota State.  Cold weather enhances the growth of certain respiratory organisms inside the calf’s nose and upper respiratory tract, and the more bacteria there are in there, the more likely they reach the lower lung and cause pneumonia.  Cold weather also thickens the mucous and impairs the work of the cilia to remove bacteria from the lower airways.  Calves as well as many other mammals have small hairs called cilia lining the airways, and these cilia sweep bacteria and other foreign material from the lower airways up to the throat to be coughed up.  If these cilia are not as functional due to thickened mucous in cold weather, increased bacteria collect in the lower airways and increases the chance of pneumonia. 

Calves need fresh air in the calf barns, but the cold air is a problem.  Because of this, calf caretakers should check the calves even more carefully in cold weather.   Dairy heifers that developed pneumonia as calves were older on average at their first calving.  Also, dairy cows that were treated more than once as calves for respiratory disease produce 10 percent less milk in their first lactation and 15 percent less milk in their second lactation.  

Many drugs are available from your veterinarian for pneumonia in calves. Different bacteria require different drugs so if you are having failures treating calves, your veterinarian may need to get a bacterial culture to determine the specific organism causing the pneumonia so you will know the correct antibiotic to use.  Mycoplasma is an organism that is very difficult to treat and requires specific antibiotics, so culturing is a good idea.