The goal of a vaccination program is to prevent the incidence and severity of infectious disease. The payoff, however, comes in the huge dividends that result by reducing the incidence of open cows, lost pregnancies, poor-performing calves and calf death loss.
Vaccination doesn't completely prevent infection; it just stimulates the development of immunity. Thus, if the animal contracts the disease, the severity should be less.
Two Vaccine Classes
There are two classes of vaccines — killed vaccines and modified live (MLV) or attenuated vaccines.
Killed vaccines are purified protein derivatives of specific infectious agents. The proteins are mixed with an adjuvant — a chemical carrier designed to enhance the effect of the vaccine and the recognition and response of the immune system.
The response generated by a killed vaccine is generally not as strong and is shorter lived than that of an MLV product. Many different killed viral and bacterial (bacterin) vaccines are available.
MLVs, on the other hand, are purified preparations of live infectious organisms. The live portion of the vaccine is attenuated (deactivated) so it won't cause significant clinical disease. Many viral and some bacterial vaccines are available in this form.
After vaccinating with an MLV, the organism in the vaccine multiplies in the body. Because the immune system interprets the vaccine organism as a naturally occurring infection, it responds by developing antibodies. Thus, the animal's susceptibility to the disease at a future time is reduced.
Because they contain live organisms, MLVs carry the risk of inducing the clinical disease associated with the vaccine, such as abortion.
Toxoids are a class of vaccines used to combat diseases caused by bacterial toxins. They're prepared from the actual toxin produced by the bacterial organisms. This vaccine group primarily applies to the clostridial diseases.
Toxoid vaccines retain their ability to stimulate an antibody response but have lost their toxicity during the vaccine preparation. The resulting antibodies have the ability to neutralize the toxin and thus prevent disease occurrence.
Here's a suggested year-round vaccination program for the beef cowherd.
The Calf. The first line of defense for a calf is its mother's colostrum. This protection, however, diminishes within a few months. When the calf's immunity level declines and the animal is exposed to a disease challenge greater than it can handle, the animal gets sick.
Most calves can be effectively vaccinated as early as four to six months of age. Both MLV and killed vaccines may be used, but MLV vaccines are generally believed to provide a better immune response in calves.
Before using MLVs on nursing calves, make sure the dams have been adequately vaccinated against these same agents. This will reduce the risk of vaccine virus that may be shed by the calves causing reproductive problems in the cows. This procedure isn't completely without risk, but it greatly reduces the cow exposure risk when using an MLV on calves that are still nursing their dams.
All calves should be vaccinated with:
A 4-way viral vaccine against infectious bovine rhinotrachaeitis (IBR), bovine viral diarrhea (BVD), parainfluenza-3 (PI3) and bovine respiratory syncytial virus (BRSV).
5-way leptospirosis vaccine, which is often included with the viral vaccines.
7-way clostridial vaccine. An 8-way should be considered in areas where the disease redwater is a concern.
Tetanus toxoid also may be recommended in high-risk areas of the country.
Booster vaccination with BRSV, 5-way leptospirosis bacterin and clostridial toxoid must be administered in three to four weeks after this primary vaccination. If a killed viral vaccine was used, all components of that vaccine must receive a booster. Failure to provide this booster will result in failure of these vaccines to stimulate an immune response.
It's preferable to perform the booster vaccination at least 30 days before weaning. This provides the highest level of protection for calves as they confront the stress of weaning.
Some producers also may elect to administer a dose of intranasal IBR/ PI3 at weaning to provide additional protection against viral respiratory diseases at this stressful time.
Brucellosis vaccination is performed by your veterinarian and is recommended for all females up to one year of age. Many states require a brucellosis vaccination for interstate transport of cattle. Some states also require a negative blood test within 30 days of interstate shipment. Check with your veterinarian for the destination state's requirements.
Herds utilizing natural service should also include vibrio (Campylobacter) vaccination for all replacement heifers 30 days to seven months prior to the breeding season. Some of these vaccines require a booster and some do not, so read the manufacturer's label carefully.
The Cowherd. Cows should receive at least one set of booster vaccinations every year. This would include a 4-way viral, 5-way leptospirosis, clostridial C&D toxoid and vibrio vaccines for respiratory, reproductive and calf intestinal diseases.
The viral vaccine can be an MLV if the cattle aren't bred. This annual vaccination is typically given at weaning, pregnancy examination or prior to calving — times at which cows are typically pregnant. Thus, a killed viral vaccine should be used.
Calf scours vaccines are recommended on a case-by-case basis. If scours have been a problem in the past, vaccinate. To be most effective, vaccinate the cow for calf scours a minimum of 60 days before calving. This allows sufficient time for an immune response prior to secretion of antibodies into the mammary gland.
The level of vaccination program for a cowherd depends on four factors:
The local level of threat or exposure to differing diseases.
How much risk the herd manager is willing to assume.
Cost-benefit analysis. If the cost of vaccination outweighs the level of risk, then adjust the program accordingly.
Whether the calves will be sold and transported out of the local area. What risk will they be exposed to in their next environment?
This outline is only a suggestion. Each producer must tailor a program to meet their specific herd's needs. The best sources of herd health advice are local veterinarians, who will know your area's level of disease exposure. You also can consult local Extension personnel.
Editor's note: Recent USDA research indicates that the timing of parasite control can affect moderate to heavily parasitized calves and yearlings' immune response to vaccination. See April 2001 BEEF, page 22, or visit www.beef-mag.com . Click on the icon “USDA parasite control research.”
Rob Callan, DVM, and Bob Mortimer, DVM, are practitioners at Colorado State University in Fort Collins. Dan Kniffen is an Extension beef specialist at Penn State University in State College.