Newborn calves gain temporary (passive) immunity against disease when they ingest colostrum from the dam — since this “first milk” contains maternal antibodies. After a few weeks or months this temporary protection begins to wane, however, and calves must build their own immunities. Vaccinating calves at the proper time can help protect them until weaning. Vaccinating them too soon, however, may not stimulate much immune response. If the calf still has maternal antibodies in its system, these tend to interfere with building its own immunities.
Thus the big question is when to vaccinate, and with what, for optimum immunity response in the calf. Dr. Steve Hendrick, an associate professor of Large Animal Clinical Sciences at the Western College of Veterinary Medicine in Saskatoon, says the first step is to discuss a herd health program with your own veterinarian, but there are some general guidelines that may be helpful.
“Here in Western Canada we advise a lot of our clients to use a BVD vaccine, and it’s usually a 5-way modified live virus vaccine. This, along with a clostridial vaccine, is probably most important for calves. Regarding clostridial products, I commonly use a 9-way vaccine covering nine different clostridial diseases,” he says.
There are additional vaccines that are important for calves in some regions. “On ranches that have a lot of summer pasture pneumonia, some veterinarians are advocating the use of a vaccine against Mannheimia (what we used to call Pasteurella haemolytica) or Histophilosis. I don’t routinely recommend this, but I do have herds that have problems with these bacterial infections. History often repeats itself. If a herd has had a problem in the past, it’s probably a good idea to add this vaccine to prevent problems in the future,” says Hendrick.
The big debate is when to give calves these vaccinations. “The majority of my clients are still vaccinating their calves at about one to two months of age, when they are branded. There are some situations, however, where the calves are born later in the season, out on grass — in May and June — and the ranchers found it was so hot and dry in July when they tried to bring them in for vaccinating, that we started vaccinating the calves at birth instead. The stress of trying to vaccinate them in July was too much,” he says.
“In a couple of herds we switched, and now give their vaccinations at birth. This isn’t ideal; it wouldn’t be my first choice. But faced with the decision of whether to vaccinate at birth or not giving any vaccines, we chose to vaccinate the calves at birth. I can’t honestly say we’ve had worse results. We don’t know whether this means the calves didn’t have enough of a challenge these last few years, or that the vaccine is helping.”
He also talked to some of the drug company technical services veterinarians about using clostridial vaccines early. “Even though it says on the label to not give this before one month of age, I don’t think we’ve seen more reactions to the vaccine in the very young calves. We also haven’t lost calves to blackleg or some of the other common clostridial diseases, so I feel comfortable giving the clostridial vaccination at birth, as well. The cow herds have been vaccinated and boostered on a regular basis, so their calves may also be getting good protection (at least temporarily) from colostrum,” says Hendrick.
“The herds that I know of that are using a Pasteurella and Histophilosis vaccine seem to be doing all right. Novartis, for instance, has done quite a bit of research with their product and have found that it is efficacious when given at birth. They have good data now for recommending its use in young calves,” he says.
The best age for giving BVD and IBR vaccines is still debatable. “From what I’ve seen in the literature, if you vaccinate calves that have high levels of maternal antibodies from colostrum, the thought has always been that those antibodies will basically mop up the antigen in the vaccine and the animal won’t develop a good response,” says Hendrick.
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However, there are two types of immunity. “One is cell mediated; there are some immune cells that are very non-specific and they clean up whatever foreign material they see. This is the first part of the immune system that develops and is very important for most of the diseases the calf faces. We believe there is probably an increase in this type of immunity with early vaccination, even though we might not see a big increase in titres or antibody response. That’s more secondary. We feel that even if these calves do get exposed to the disease, they at least have good cell-mediated immunity from the vaccine. We feel this is very important for some of the viral infections anyway. This is why I feel OK about switching a couple of these herds to vaccinating at a younger age. If the calves are being branded at a later age, however, I still recommend vaccinating at branding time,” he says.
It is important to work with your veterinarian, and come up with a plan based on what has worked in the past for your herd, and what diseases you have in the herd. “We see some baby calf pneumonia that probably isn’t Pasteurella. It’s probably BRSV or some other virus, rather than bacterial. If you’ve worked with your veterinarian and made a diagnosis, you can be more specific about which vaccine you choose,” he explains.
There is an intranasal vaccine and it may work in some herds. The logic behind it makes sense; you are stimulating local immunity in the nasal passages, where the virus would normally enter. “You are basically stopping this entry, or minimizing the viruse’s ability to get into the body and set up an infection. It’s almost one step earlier than giving the vaccine under the skin, to be absorbed by the body. In that scenario the virus gets into the nose and goes on into the body before the generalized immune response can attack the virus,” he says.
“Some ranchers swear by the intranasal vaccine and say it has worked very well for them, and others have used it and don’t think it has helped much. I think it comes down to what the calves are being exposed to. If the disease is bacterial rather than viral, the viral product won’t help,” says Hendrick. You have to know your enemy, in order to choose the right weapon.
This is why you need to work with your veterinarian and get some diagnostics on what is causing disease in your particular herd. Then you are better able to select the appropriate vaccines, rather than just using what your neighbour uses, or going by what you read in advertisements for certain products.
“In general, however, the core vaccines for any herd would be at least a BVD vaccine and clostridial vaccine. We need to protect the calves from what’s out there, and it can be a challenge to get them safely through the first months of life and keep them healthy through weaning age,” he says.
Summer pneumonia can be a difficult challenge, however, for some ranchers. There is some research currently being done on this, but we still don’t know all the answers. “I sat in on the American Bovine Practitioners annual meeting in Milwaukee, Wisconsin this fall and listened to some of the researchers presenting their projects. Summer pneumonia is such a broad diagnosis; it could be viral, bacterial or a combination of both. It may also be triggered by dust, being moved out to pastures, and there may be different contributing/predisposing factors for each herd. It is a huge challenge to come up with clear and concise recommendations.”
Effective preventive measures must be herd specific. “If we could recognize a few key patterns, and then see these types of risk factors in a herd, we might be able to recommend some things to try,” he says.
Different ranches are calving at different times — anywhere from January to June, and also some fall-calving herds. This makes it much more difficult to make generalized recommendations for calfhood vaccination programs, so it pays to work with your vet to develop a program to fit your own herd.
Other management factors are equally important. “It’s great to vaccinate the cows ahead of calving to make sure they have a high level of antibodies in colostrum, but if the cow doesn’t have a good bag or isn’t a good mother and the calf can’t nurse, he is not protected. The environment and the weather can also play a big role.” If you get a cold, damp spring, it may also be difficult for calves to have optimal conditions for staying healthy.
Keeping calves healthy is not always easy because there can be so many factors involved.