Newborn calves gain temporary (passive) immunity from 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 age. Vaccinating 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. The body sees no need to respond.
Dr. Chris Chase, department of veterinary and biomedical sciences, South Dakota State University, says most calves probably get a good response to vaccinations by about three months of age.
“It all depends on how much protection the calf received at birth — how much colostrum, how soon (for maximum absorption of antibodies) and how good it was,” says Chase. “In most herds, you won’t find 100 per cent of the calves fully protected; it’s more like 70 to 80 per cent. It also depends on the diseases in a herd.
WATCH FOR BRSV
“BRSV (Bovine Respiratory Syncytial Virus) is notorious for having maternal interference at low levels that can last for a long time. If the calf received antibodies against BRSV from colostrum, it may not gain much immunity from an injected vaccine — unless it is adjuvanted — until those maternal antibodies are gone from his system. (An adjuvant is an immunological agent that modifies the effect of other vaccines while having few if any direct effects when given by itself.)
And note, BRSV is frequently isolated in pneumonia of calves and yearlings. Because of its frequent occurrence and tendency to cause infections in the lower respiratory tract, BRSV represents a very important virus in the bovine respiratory disease complex (BRD). Infection is followed by specific clinical signs. The method of transmission is not clear, but droplet infection seems to be most likely. BRS virus destroys part of the upper airways, predisposing the respiratory tract to further infection. Results of recent research consider the severe clinical signs such as emphysema and edema to be part of allergic reactions to infection.
“Producers need a vaccination plan,” says Chase. “They might decide to give calves vaccinations for IBR and BVD, but those two diseases are generally not an issue in young calves. You need to be more concerned with these diseases as calves approach weaning.
“Some herds, however, have trouble with summer pneumonia in young calves, and BRSV is a problem. In these cases there are a couple of approaches. One is to use the intranasal vaccine, which has the ability to get around the maternal antibodies. The other thing a producer can do is use an adjuvanted vaccine. In most cases people think that only an inactivated vaccine is adjuvanted, but we do have some adjuvanted modified-live vaccines. We don’t yet know, however, how effective these vaccines are against BRSV in calves with maternal antibodies.”
Chase says if producers know there is a summer pneumonia problem, BRSV is usually the culprit. There’s no vaccine just for BRSV, however. Producers must use the combination product containing BRSV-IBR-BVD-PI3, even though at this age in calves the BRSV is the only thing producers need to be concerned about.
Proper diagnosis is crucial. “Producers need some indication about what they are dealing with,” says Chase. “There are some tests now, using deep pharyngeal swabs and other ways to get material from deep in the back of the throat, to get a more accurate diagnosis. With BRSV, it used to be unrewarding to pay for diagnostics because they’d just take a Q-Tip swab from the throat, and this was hit or miss. The deep pharyngeal swab gives better results.
“Some of the work we’ve done with inactivated vaccines shows that even after one dose of vaccine, some of the T-cells are turned on within two weeks of vaccination. We can see BVD antibodies coming up, even after 14 to 21 days, which is exciting, because we generally don’t see much of a response when we vaccinate with just one dose of inactivated vaccine (without following it with a booster). To use just one dose would clearly be off label because we don’t have enough data to say you’d be safe with just a single dose.”
At this point, says Chase, the intranasal vaccine gives the most likelihood of success and least likelihood of failure, in young calves. From two weeks up to three months, this treatment makes the most sense, particularly if producers are worried about BRSV. The adjuvanted modified-live vaccine, where a single dose is given, also has some usefulness, but he says researchers don’t have enough data yet on treating young calves with agents other than BVDV. The intranasal vaccine, by contrast, has plenty of data to show that it works against BVDV, he says.
For calves, depending on what the producer must deal with, there are also the seven-way clostridial vaccines that can be given at this age. “The interesting thing with these is that the literature tells us that if there are maternal antibodies present these might not work,” says Chase. “But field experience time and time again shows that those vaccines definitely have some efficacy. This is especially true if you are looking at C. perfringens in young calves, or blackleg.
“You can give these vaccines and not have to worry so much about problems with maternal antibody interference. Part of the reason is that with clostridia we are actually vaccinating against an exotoxin. This is a simpler antigen, and a little easier for the immune system to see and attack, compared with some of the viruses (and all the processes that must happen to protect against those). If a producer is having problems with enterotoxaemia, for instance, the calves can be vaccinated at a very young age, even if the cows were vaccinated during pregnancy to stimulate high levels of maternal antibodies in the colostrum.
Chase says other causes of summer pneumonia might be due to Mannheimia hemolytica or Pasteurella multicida. Producers might use either the live or inactivated vaccine for treatment. Some research shows that even with the inactivated vaccines there is some maternal interference with these vaccines, up to at least four to six weeks of age. He says producers have to consider a strategic question regarding the age at which calves are having problems.
As a rule of thumb, many ranchers give calfhood vaccinations at branding time. “When vaccinating calves at this age, the goal is often just to prepare them for whatever they will encounter at weaning time,” says Chase. “It’s like a setup vaccination that will then be boostered at weaning. If you want to give a vaccination just prior to or at weaning, it’s good to have this initial injection at an earlier age.”
Providing proper protection is all about timing. Producers need to work with their veterinarian to plan a strategic vaccination program that best fits their situation and management. “Working with your veterinarian, evaluating herd history regarding disease (what you’ve dealt with in the past and when it has occurred) can be very helpful. The idea that one size fits all does not work,” says Chase.
“Giving calves vaccinations at two to three months of age has its benefits. A lot of the animals will develop some response, though not all of them will be protected against respiratory pathogens at weaning time. I like the intranasal approach, but if the producer doesn’t have a problem with BRSV in young calves, there’s no need to go that route.”
HeatherSmithThomasrancheswithher husbandLynnnearSalmon,Idaho.Contact herat208-756-2841