High humidity, moisture, and increased levels of air contaminants due to ineffective ventilation can lead to significant health issues in our animals. This is especially of concern to our most sensitive sub-population, newborns and the very young. Even calves that receive adequate colostrum and a good nutritional start to life will have health challenges if they live in highly contaminated environments. Diarrhea (scours) is the first obstacle calves must overcome with respiratory disease (pneumonia) as a close second. Poor air quality due to inadequate ventilation in the calving barn can lead to increased levels of both scours and respiratory disease in calves.

Inadequate ventilation results in increased levels of air contaminants. Some of the contaminants that most affect calf health include:


  • A breakdown product of protein metabolism. Nitrogen wastes in urine and manure are excreted primarily as urea and then converted to ammonia in the soil/bedding.
  • Ammonia volatilizes (evaporates) into the air at higher rates in warm/moist conditions.
  • Ammonia begins to have an adverse effect around 20-25 ppm (we begin to smell it at 10-15 ppm)
  • Ammonia causes direct irritation to the respiratory mucosa and decreases the efficiency of physical defense mechanism in the airways.
  • High levels (over 100 ppm) can cause direct damage.
  • Increased stress due to constant exposure to ammonia can weaken calves’ ability to fight off other diseases, such as scours.

Hydrogen Sulfide

  • A breakdown product of animal and organic wastes (manure, bedding, etc).
  • Has a characteristic rotten-egg smell.
  • Respiratory irritant, leading to increased risk of respiratory disease.
  • High exposure levels can lead to coma and death.


  • The outer layer of gram negative bacteria.
  • Highly immunogenic – which means that breathing in endotoxin causes an immune reaction similar to disease, without truly causing a disease.
  • The induced inflammation reduces the body’s ability to fight off true disease challenges from viruses and living bacteria.


  • BRSV, IBR, BVD, parainfluenza-3 virus, rotavirus and coronavirus all survive longer in the environment in moist, warm conditions.
  • Increased levels of viral particles in the environment increase the risk of infection.


  • Mannheimia haemolytica, Pasteurella multocida, Mycoplasma bovis, Histophilus somnus, and others all survive longer in the environment in moist, warm conditions.
  • Increased levels of bacteria suspended in the air increase the risk of infection.
  • High levels of the above listed contaminants increase the risk of bacterial infection.


  • Though not a problem in and of itself, high moisture levels increase the loading rates of the contaminants described above.
  • High moisture levels limit the amount of drying that occurs in a building and can lead to wet ground conditions.
  • Due to a lack of drying, more cleaning and bedding materials are required to maintain dry, comfortable ground conditions in a calving barn. Dry ground conditions promote calves nesting in the bedding and decrease heat loss to the ground.
  • Moisture levels are the easiest to observe/measure and are correlated with levels of other contaminants.

From a management standpoint it is easy to think that temperature is a major factor in the success of newborn calves, and it certainly does make a difference in very cold/windy environments (January-March, South Dakota). However, raising the temperature in a building by holding animals in a building, insulating the building, and minimizing the ventilation rate at the expense of air quality does not benefit a calf’s health. It can, and often does, lead to reduced health outcomes and predisposes to long term ill effects. In the next article we will examine the environmental requirements of calves, and options we have to manage the indoor environment of calving facilities.