Calf immunity is crucial for health and productivity
Published on Feb. 22, 2020
Illness occurs when the body is overwhelmed by infection. A healthy animal with strong immunity is less likely to become sick than an animal with poor immunity.
The body’s ability to fight off pathogens is developed in a complex process in which it creates specific weapons for fighting specific invaders.
Antibodies
One type of weapon involves production of antibodies. When pathogens, such as viruses or bacteria, invade body tissues, causing damage by multiplying and creating toxic products, it stimulates production of antibodies, serum protein called immunoglobulin, to react with the invading agent and neutralize it.
These antibodies are carried throughout the bloodstream. The main role of one type of lymphocyte, white blood cells, is to produce antibodies, proteins that can neutralize certain infectious agents.
If an animal already has antibodies against a specific disease organism, then any time that organism invades the body again an army of white blood cells and antibodies converge on the site to kill the invader.
Exposure to one strain of an organism may result in immunity to that specific strain, but might not protect against other strains of the same organism.
Antibody immunity depends on the level of exposure, stresses on the animal, nutrition status and current health. A severe outbreak of disease in a herd may eventually break down a healthy animal’s immunity and will overwhelm a severely stressed animal’s defense even sooner.
Vaccination
Vaccination can stimulate production of antibodies. The vaccine serves as the antigen, like an invading pathogen. The body builds protective antibodies to fight the perceived invader.
Then, when the animal comes into contact later with the actual infectious agent, the antibody is present in the bloodstream and can inactivate the pathogen.
If enough antibodies are present to inactivate the agents that invade the body, the animal will not get sick, and the invasion stimulates rapid production of more antibodies for future protection.
With vaccination and natural exposure to various pathogens, a cow develops many antibodies and strong immunity. During the last part of pregnancy, she puts these antibodies into colostrum so her calf will have instant immunity right after he suckles.
University of Calgary Professor of Production Animal Health, Faculty of Veterinary Medicine Dr. Eugene Janzen says the first thing to consider regarding the importance of calf immunity is the level of disease risk.
“The second thing is, research is now showing we can vaccinate a baby calf and the immune system remembers, even though the calf already has passive immunity from cow’s colostrum. We can do early vaccination two ways -intranasally to create a local immunity or the calves can be vaccinated systemically,” says Janzen.
In some situations, the calf needs local immunity, especially for things like intestinal tract disease. Most gut infections remain local, meaning they stay in the gastrointestinal tract, unless the infection goes systemic with bacteria and toxins leaving the gut and getting into the bloodstream to create acute toxemia.
Some researchers have looked at the question of how to get a local immunity in the gut to protect against scours.
A number of problems tend to be local, and systemic vaccines don’t give much protection.
“Probably the poster child for local immunity is pinkeye. The literature demonstrates vaccinations of all kinds are inadequate for good protection. The thing veterinarians and pharmaceutical companies haven’t faced is that we should drip the antigen into the eye rather than injecting it systemically,” Janzen explains.
He continues, “Vaccinating is a challenge, for some diseases, but if we vaccinate a baby calf, even at day one, in the face of passive immunity, when we revaccinate those calves at weaning, the body remembers. The second vaccination acts as a booster.”
“Some people ask about this because they don’t brand their calves, the typical time for vaccinating, so when should they vaccinate those calves?” he asks.
“They wonder if they could vaccinate soon after birth, at the same time they are tagging them and putting bands on the bull calves. So, I ask them what they are going to vaccinate for and what time of year they calve,” he says. “If they are calving later, during good weather and on green grass rather than in corrals behind the barn, the risk of intestinal diseases in young calves is considerably lower.”
“Probably the only thing they are truly at risk for is clostridial diseases like blackleg, malignant edema and redwater, all of which are acute and highly fatal diseases and perfringens, the clostridia that cause toxic gut infections. The risk for clostridial infections is always there, and for most calves it’s still the most important thing we need to vaccinate for,” he says.
There may also be some risk for respiratory diseases like summer pneumonia. Some operations have fewer health problems if calves are vaccinated for respiratory diseases before being turned out on summer pasture or range.
“Some animal welfare groups are actually more concerned about commingling of calves from different sources, including auction yards, than about various procedures we do, like dehorning and castrating,” he says. “I remember looking at pens of bawling calves at a feedyard where there were 300 calves in a pen. Looking at the sales tickets, those calves may have come from as many as 100 different original owners.”
“No wonder we have health problems in put-together pens of cattle. Anything we can do as an industry to circumvent commingling of calves will be very helpful,” he says.
This all goes back to how they are managed and how they were vaccinated initially.
“Cattle producers might use different vaccines under certain conditions, taking the risks into consideration regarding when to vaccinate. If we vaccinate a baby calf we may not get a strong titer, but we’ll get enough response to provoke the immune system into remembering in the fall when we vaccinate that calf again,” says Janzen.
“When calving during cold weather, cows are confined in calving lots with windbreaks and bedding and calves must be protected from freezing so they are put into the barn,” he concludes. “In this situation, we increase the risk of diseases and must become more intense and careful in our management, including vaccination, to make sure these calves don’t get sick during the first days and weeks of life.”
Heather Smith-Thomas is a corresponding writer for the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.
