Cause isn’t known | Pneumonia is a leading cause of sickness and death in the North American cattle industry
OMAHA, Neb. — Pneumonia is one of the key health problems facing young calves in Canada and the United States.
“Respiratory disease is now a big deal and we have to do something about calves that have BRD,” said epidemiologist David Smith from Mississippi State University’s veterinary college.
It is hard to know if bovine respiratory disease is an emerging problem or whether producers and their veterinarians are just more aware of it, he told the National Institute for Animal Agriculture convention held in Omaha April 1-4.
“There may be emergence of a novel agent, something that has gained a new set of virulence factors,” he said.
“It might be an agent that we thought we had control and now it is not controlled. Bovine tuberculosis is an example of that.”
He said pneumonia is a leading cause of sickness and death and probably costs the U.S. beef industry $200 million a year.
Research shows sickness occurs at different stages of a calf’s life.
Calves that get sick before 20 days of age do so because they did not receive adequate colostrum. Those in the 70 to 100 day range may have sickened because the maternal antibodies wore off and their vaccines had not kicked in.
Canadian producers are experiencing similar outbreaks, but prevalence is hard to measure, said Dr. John Campbell of the Western College of Veterinary Medicine in Saskatoon.
As well, sick calves may also be afflicted with viral and bacterial infections.
“It is usually a mixed bag,” Campbell said in an interview. “By the time they die they have bacterial infections, but it probably starts as a pure viral infection and then gets secondary bacterial infections.”
Scours was once considered the plague of young calves, but poor immunity means any number of diseases can happen under the right circumstances.
Campbell said the key is making sure newborns receive adequate colostrum from their mothers, and new research is showing early vaccination does not cancel out the benefits of maternal antibodies.
A number of products on the market work well, and more producers are using intranasal vaccines that give local immunity to young calves.
Boosters are required, which means calves that were vaccinated early in life should receive another dose when they enter the pasture and perhaps again at weaning. Time between shots depends on the product, he added.
They should be better protected in theory, but scientists are not sure how much immunity these calves have. There is no firm evidence to show that calves that were ill on the farm continue to be sickly once they go to the feedlot.
Three or four pathogens are commonly associated with BRD in calves. Cows may carry them in their nasal cavities, and calves with poor immunity may get sick.
“Cows have those viruses and bacteria in their systems and even normal calves will have those viruses, but if we stress them or they have poor immunity, we can create respiratory disease outbreaks,” Campbell said.
Smith said management can contribute to sickness.
Cold, wet, unpredictable weather can stress youngsters and allow the ever present viruses and bacteria to catch up with them.
Some blame supplemental feed, which encourages calves to huddle around and stick their noses in the creep feeder and share germs.
“It is not the creep feed. It is the system that allows the calves to get together,” Smith said.
Others have reported that more calves seem to get sick when cows were estrus synchronized for artificial insemination.
It is stressful for calves to be separated from their mothers and commingle with strangers, which probably leads to more sickness during breeding.
“All these management practices that we would consider are components of the cause,” he said.
Building herd immunity is another way to protect young calves. This is done by protecting the majority of the population and keeping the pathogen from spreading within the group.
Vaccination achieves some level of herd immunity because all the cattle get sick when the group is suddenly susceptible.
Smith said a study of more than 5,000 calf records showed bulls are more likely to get respiratory disease than heifers and steers.
Also, a two-year-old heifer with its first calf is more at risk than a mature cow that knows how to get the baby up and nursing right away to get a good dose of colostrum.