Signs of respiratory disease subtle among young calves

As cow-calf pairs are turned out to grass, we hope that most of the major calf disease problems are behind us.

However, there are occasions where cases of respiratory disease occur in calves between the ages of two and 12 weeks. The signs can be relatively subtle at first and if the calves are not observed closely, the first sign of a problem might even be a dead calf.

A post-mortem examination by a veterinarian will identify the cause of the problem, but there are things to watch for before it gets to that point:

  • sick calves may suffer from rapid shallow breathing or have more laboured breathing with an abdominal lift
  • there will usually be a persistent, dry, hacking cough in the group of calves, which is exacerbated with exercise
  • the calves may appear slightly gaunt because they are often not nursing as much as usual and often they will be less active and less likely to stretch when they rise
  • calves may have nasal discharge or excessive tearing around their eyes
  • they may have concurrent diarrhea and dehydration in addition to pneumonia
  • calves usually have a fever of greater than 40 C

This syndrome of respiratory disease in young calves is sometimes referred to as enzootic calf pneumonia and can be caused by a variety of combinations of viruses and bacteria.

Viruses implicated in outbreaks include bovine respiratory syncytial virus (BRSV), parainfluenza 3 virus (PI3) and bovine viral diarrhea virus (BVD).

In many cases, there is a secondary bacterial infection on top of the initial viral infection that may include several bacterial species. The clinical signs become even more severe as the bacterial complications progress.

Calf pneumonia is most commonly seen in housed dairy calves and can be responsible for 30 percent of all deaths of calves in dairy herds.

It is also the most important cause of death in veal calves and can be a significant problem in beef herds.

The disease is most commonly seen in crowded and inadequately ventilated conditions, which explains the higher frequency of the disease in dairy and veal calves that are often housed indoors.

In these circumstances, preventing the disease mainly involves improving calf housing, particularly air flow and ventilation.

Keeping calves within appropriate age groups and avoiding mixing calves with older animals will also help.

Housing calves in individual calf hutches in the dairy industry was intended to prevent the disease.

Beef calves, which live primarily outside, can get enzootic pneumonia because of other important risk factors that may play a role in their development:

  • calf pneumonia tends to affect calves with poor levels of immunity. They may not have received adequate colostrum at birth and their ability to fight off infection may be limited
  • nutritional stress
  • drought conditions
  • weather conditions
  • dust

I have seen several outbreaks of pneumonia occur when the calves have been exposed to an animal that is persistently infected with BVD.

The BVD virus can infect young calves and suppress the immune system, which may allow other viruses or bacteria to gain a foot hold and cause pneumonia.

Dealing with an outbreak in a cow-calf herd is more difficult because early detection and treatment is more complicated on pasture. Catching or roping individual sick calves on pasture is not easy.

In a herd outbreak, veterinarians may even recommend treating all of the calves in the herd with long-acting injectable antibiotics to limit the extent of the problem.

However, an important component of these infections may be viral, which may not respond to antibiotic therapy.

Antibiotics will be necessary to prevent and treat the bacterial complications, but the calves may still have to deal with a viral infection on their own.

A veterinarian may recommend a non-steroidal anti-inflammatory drug in combination with the antibiotic to help lower the fever and deal with the inflammation.

Prevention can be enhanced by an appropriate vaccination program in young calves and the cow herd. A veterinarian can recommend the most appropriate vaccination protocol for the herd.

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