This can result in calves being more susceptible to infection and a poor response to vaccination. Salmonella - more commonly a cause of calf scour, Salmonella can also cause and predispose to respiratory problems. Ventilation - a coughing calf spreads respiratory pathogens in droplet form throughout its airspace. If ventilation is inadequate and stocking density too high, the challenge to the calf is obviously increased. However, standing in a pen and assessing the air quality yourself maybe more helpful.
Cattle cope well with cold, unless in a draught.
Stocking - it is inadvisable to have calves of different ages in the same air space. Older, apparently recovered calves may still be carrying viruses, which will then spread to younger, susceptible calves. 5 days - E.Coli is most common. Toxin produced causes collapse of blood vessels. Treatment must be with electrolytes to expand blood volume and overcome dehydration.