Getting a young beef or dairy calf off to a good start always involves ensuring adequate colostral intake.
The calf has few antibodies in its blood stream at birth, and this first milk contains large quantities of antibodies from the dam. These antibodies are absorbed by the calf and provide important maternal immunity for the first few months of life.
We also try to help that immunity by vaccinating the cow with vaccines against scours. The cow will pass specific antibodies to the calf and make it less likely for it to succumb to diarrhea.
A large volume of research demonstrates that calves with less than adequate colostrum intake are more likely to become sick, die or weigh less at weaning and fail to reach their growth potential.
Vaccinating the calf is another way to provide specific immunity.
There are a lot of unknowns about how newborn or very young calves respond to vaccines, but we do know that the newborn calf has a functional immune system. It begins to develop in the fetus as early as 40 days into gestation, and by the third trimester it can respond to a variety of infections.
However, most calves are born with no antibodies in their blood stream, and although their immune cells function at a slower rate, the immune system is completely functional.
We also have evidence that nutrition can play a role in immune response.
Calves can have lowered immunity and be more likely to become sick or die if they have severe or chronic deficiencies in a variety of trace minerals and vitamins or if they are fed diets that are deficient in energy or protein.
We think the immune system can recover quickly if the deficiency is corrected early, but more research is needed to explore the interaction between nutrition and immunity.
Vitamin E is a common deficiency in calves in Western Canada, which has been associated with outbreaks of neonatal death in some herds.
We have traditionally assumed that calves would not respond well to vaccinations if they had high levels of maternal antibodies in their system from colostrum. These maternal antibodies were expected to “bind up” the vaccine and prevent the immune system from responding to it.
However, studies have now shown that young calves can respond to vaccination in the face of maternal antibodies.
The vaccines, when given early, can help prime the immune system for a memory response when the maternal antibodies are gone. They can also help prolong antibody levels in the calf.
Vaccinating young calves can also influence other aspects of immunity, which are not as obvious as antibody levels and have a positive effect.
Several vaccine companies are now marketing intranasal vaccines for some respiratory viruses. They may be superior to injectable vaccines for young calves with maternal antibodies present, but more research is needed.
Clinical field trials are the best way to answer questions about vaccine efficacy, but they are more likely to be performed in large dairy operations than beef cow-calf herds.
We still have lots of questions about immunity in young calves and how they respond to vaccines, particularly in calves younger than one month. These young calves may respond better to intranasal vaccination, but we need more information on the factors that limit vaccine efficacy.
However, the immunity from intranasal vaccines may not last as long, and we are fairly certain that calves are more likely than adults to require booster vaccinations. These boosters are usually given two to four weeks after the initial vaccination, but this may not always be practical in some herds.
Most producers are adequately vaccinating young calves for clostridial disease, but respiratory disease is the other major risk. These outbreaks tend to occur at six to eight weeks of age, which means vaccines will have to be administered at least one month before disease occurrence.
This may necessitate vaccinating young calves that have high concentrations of maternal antibodies.
It would probably be ideal in high risk situations to provide at least one booster vaccination after the initial vaccination and before the greatest risk of disease occurrence. In these situations, veterinarians may have to ask producers to use vaccines in calves as young as a few weeks of age.
We know that pre-weaned calves can respond to vaccines as early as the first day of life, but the response is probably better in calves one month old or greater. Calves respond to vaccines in a similar fashion as adult animals once they are five to eight months old.
Intranasal vaccines have shown advantages when vaccinating young calves and should be considered as part of a herd’s vaccine protocol.
Vaccine programs should be developed in consultation with a herd veterinarian, who can provide detailed information on the timing of necessary vaccinations.
John Campbell is head of Large Animal Clinical Sciences at the University of Saskatchewan’s Western College of Veterinary Medicine.