A year-around program for beef cattle herd health
April 14, 2006
by Daniel M. Kniffen Ph.D.
Robert J. Callan DVM
Robert G. Mortimer DVM
Colorado State University
An effective vaccination program can have a significant impact on reducing cost of production in the cowherd. Costs can be calculated in several ways, some of which include: open cows, lost pregnancies, low performing calves and calf death loss. The ultimate goal of a good vaccination program is to help reduce the incidence of these cost through disease prevention.
The first line of defense for a young or newborn calf is the immunity acquired through the colostrum it consumes when it is first born. The young animal develops a natural level of protection. However this protection begins to diminish over the first few months of its life. Disease results when the level of immunity that and animal has declines to a lower level and the animal is exposed to an outside stress that exceeds the current level of immunity. For example, when calves are weaned, they experience change in their environment of not only losing their mother as a companion, but also have to fend totally for themselves for the first time. Many times this event results in calves not consuming a full diet. This change in intake compromises their ability to ward off disease challenges. When the disease exceeds their ability to resist it the animals become sick.
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A vaccination does not prevent the disease from occurring; it stimulates the animal to develop an “immunity” against a disease. Even after developing an immunity to the disease the animal is not necessarily totally protected from contracting a disease. However, if the animal does contract the disease it should be less severe than if the disease was contracted without the immunity or defense built up by the vaccination program. Vaccination is the process of exposing an animal to an antigen with the intent to stimulate an immune response. The process of vaccination does not guarantee immunity. Immunization occurs when the animal mounts an immune response following vaccination. However, immunization does not guarantee protection. Through the understanding of the relationship between vaccination, immunity and the available vaccines an informed decision can be made regarding the development and implementation of an effective herd health program.
Vaccines are divided into one of two classifications. They are designed to stimulate the development of immunity against either viruses or bacterial infections that cause diseases. Within the group of vaccines designed to combat the effect of viruses there are two types of virus vaccines available: killed vaccines and modified live vaccines.
Killed vaccines are purified protein derivatives of the specific infectious agents. The proteins are mixed with an adjuvant. The function of the adjuvant is to be a chemical carrier designed to enhance the effect of the protein and enhance the recognition and response of the immune system. The response generated from the use of a killed vaccine is generally not as strong and is shorter lived than the response from the use of modified live vaccines.
Modified live vaccines are purified preparations of live infectious organisms. The live portion of the vaccine has been attenuated (deactivated) so as not to cause significant clinical disease. After vaccinating with a modified live vaccine (MLV) the organism in the vaccine multiplies in the body and presents itself to the immune system in a mode similar to the naturally occurring disease. The immune system responds by developing antibodies to the disease, thereby reducing the susceptibility to the disease in the future. MLVs produce higher and longer lasting levels of immunity as compared to killed vaccines. However, because of the mode of action of MLVs they also carry the risk of inducing the clinical disease associated with the vaccine. Additionally, before MLVs can be used on calves that are still nursing cows, the cow herd must have a vaccination program in place for a couple of years that has included the use of MLVs on the cows while they were not pregnant. This procedure is not completely without potential risk. However, it will go a long ways toward reducing of the risk of using MLVs on calves while they are still on the cows.
Toxoids are the class of vaccines used to combat diseases caused by bacterial toxins. The vaccines are prepared from the actual toxin produced by the bacterial organisms. This group of vaccines is primarily applied to the clostridial diseases. Toxoids contain purified preparations of the protein toxins that are chemically denatured. The vaccines retain their ability to stimulate an antibody response, but have lost their toxicity. The developed antibodies have the ability to neutralize the toxin and thereby help prevent the occurrence of the disease.
A suggested year-round vaccination program for the beef cowherd might include the following protocol:
– All calves 4 to 6 months of age should receive a modified live vaccination for the respiratory diseases (IBR, BVD, PI-3, and BRSV). Remember MLVs offer stronger immunity than provided by the killed vaccines. Calves must receive a booster shot for the BRSV component at about 21 days to maximize the full protection offered by these vaccines. If a killed virus vaccine is used, it must also be followed with a booster at about 21 days for all components of the vaccine.
Calves should also receive a dose of Clostridial C and D and tetanus toxoid. Calves should also receive a booster at the 21-day interval. The booster shot should be administered 30 days before weaning. This routine will provide the highest level of protection for calves as they confront the stress of weaning.
If the cowherd health program is not up to recommendation an alternative is to administer a dose of intranasal IBR/PI3. This can be administered at weaning to protect against respiratory viral diseases.
However, for maximum protection, the calves should follow the modified live vaccination program outlined above. This regimen can be started about two weeks after the calves have been weaned.
– Depending on the location of the cowherd in the U.S. and the exposure to brucellosis, a brucellosis vaccination might be considered for all females in the herd up to 12 months of age. Some states will require vaccinations while others will require a clean brucellosis test 30 days prior to interstate shipment.
– The suggested cowherd vaccination program will require working the cows at two different times of the year for maximum protection. During the period following calving, and preferably at least 30 days prior to breeding, the cows should receive a four-way modified live vaccination for the respiratory diseases. The cowherd should also receive a vaccination for leptospirosis. This vaccine should include all five serovars of lepto and is often included with the respiratory vaccine.
– The other round of vaccinations for the cowherd preferably should be given 30 to 45 days prior to calving. This group of vaccinations should include a killed respiratory virus and Clostridials C and D and tetanus. Many producers may elect to give this round of vaccinations during fall weaning while working the cows through the chute at that time. This is better than not vaccinating this group at all, however it is more effective giving it closer to calving.
– The use of calf scours vaccine should be decided on a case-by-case basis. If calf scours has been a problem in previous years then a vaccination program should be developed. This vaccination needs to be delivered in the 30 to 45 day window prior to calving to be most effective.
The level of vaccination program for a given cowherd will depend on four simple factors. First the local level of threat or exposure to differing diseases must be determined. Next, as the herd health manager you must decide how much risk you are willing to assume. Third the cost-benefit analysis must be calculated. If you believe the cost of applying the various vaccines outweighs the level of risk you are exposed to then you need to adjust your vaccination program accordingly.
Finally, if the calves are going to be sold and transported out of the local area, what risk will they be exposed to in their next environment?
The best person to ask for advice on a herd health program is your local veterinarian. The veterinarian visits enough clients in an area to know what level of disease exposure is present. Your local extension agent may also provide some information at the local level. Remember these are only suggestions. Each individual must tailor a program to meet his or her specific needs.