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Preventing Disease
Immunology, stated as simply as possible, is the study of the process of becoming immune to diseases. In livestock production the more animals are disease free the more efficient an enterprise. Preventing disease is more efficient than treating disease or eradicating it.
Stimulating immunity at sufficient level to prevent a specific disease prior to exposure to the disease is the best approach to animal health.
Disease organisms in a general sense are antigens. Antigens are primarily protein substances that are recognized by an individual animal's defense system as foreign to the body. When a calf's defense system encounters an antigen, such as a virus or bacteria, it tries to destroy it. At the same time the defense system builds a memory of the antigen that allows it to respond more quickly and efficiently the next time it encounters the same antigen.
On the first encounter with an antigen the defense system may require from 48 hours to two weeks to build a protective immunity. The response rate depends on the antigen encountered and the individual animal. Once the memory system is stimulated, the next encounter with the same antigen triggers a response within a couple of days and boosters immunity against that specific antigen to higher levels.
The defense system is quite complex. Basically white blood cells respond to any antigen invasion. A group of white blood cells are made of many types. Each type has a different function. Some attack and engulf antigens, others produce chemicals and kill viruses and bacteria when released. Some white blood cells are programmed to stimulate antibody production and some stimulate a memory response.
Generally antibodies are associated with defense against disease but antibodies are only one part of an overall immune response. Antibody responses are measured by titers in blood. A high titer indicates good protection or potential for longer protection. However there is variability between disease antigens. Sometimes a calf with little or no antibody titer withstands a challenge from a particular antigen. In these cases the calf is protected by other cellular parts of the immune system. These cellular parts are sufficiently high to protect against that particular disease organism.
Vaccination is intended to stimulate immunity against disease. Vaccination alone cannot protect cattle. A particular animal must first respond to vaccination and then build adequate immunity. Responding requires good body condition. For cattle to respond optimally they need to be in good body condition and in good nutritional status. Building immunity requires protein and proper levels of various trace minerals. Vaccination does not equate to protection. Protection requires nutritionally capable, susceptible cattle and actual response to the vaccine.
More Basic Immunity Information
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