Understanding Calf Immunity
Working to eliminate health issues in young calves is a critical first step in saving the beef industry millions of dollars annually through economic losses attributed to wasted feed resources, purchased pharmaceuticals, reduced performance and increased mortality.
Fast, timely reaction of the immune system from birth on helps ensure calves perform at optimal levels. Understanding the role immunity plays in setting the stage for the calf’s future is vital in preparing the calf for a lifetime of success. Active and passive immunity, combined with a planned management and nutrition strategy, form a firm foundation for calf productivity and can put ranchers on a path toward economic efficiency.
This excerpt from an article produced by Oregon State University gives an overview of the cattle immune system:
Active and Passive Immunity – Immunity is the resistance of the animal to a specific disease. Active immunity is acquired when the animal is infected by a specific pathogen, creates a “memory” against it, and successfully eliminates the disease and pathogen. The next time the animal is infected by the pathogen, the adaptive immune response will be faster and stronger (Figure 2), quickly eliminating the pathogen and preventing the disease. A common example is chicken pox in humans; once you have it you’ll never have it again. Vaccination is also an example of active immunity. By injecting the animal with a killed or weakened pathogen, which won’t be harmful enough to develop the disease, the immune system creates the “memory” and learns how to fight it if an infection occurs. Passive immunity occurs when the animal receives antibodies from an external source, such as another animal. The classical example of passive immunity is the transfer of antibodies from the cow to the calf via colostrum. This transfer is extremely important to newborn calves because their immune system is not mature enough to develop its own antibodies. The calf should be immune to most of the pathogens present in the environment because the dam has already been exposed to them and developed protective antibodies. Another example of passive immunity is the administration of specific antiserum or antitoxin to sick cattle or calves that did not receive enough colostrum.
Managing Cattle Health
In commercial beef operations, cattle are frequently exposed to health challenges. These can be bacteria, viruses, parasites, and toxins coming from the feed, air, water, wildlife, other cattle, and even humans. Stress is also an important factor regarding cattle health. Extreme temperatures, handling, transportation, weaning, and comingling are stressors that can suppress the immune system of cattle, but also trigger inflam¬matory responses. Maintaining cattle in good health is not only important for animal well-being, but also has implications on animal productivity. The immune system, as well as any other body functions, requires a significant amount of nutrients to work properly. When the animal is infected by a pathogen, a significant amount of the consumed energy and protein that were supposed to support productive functions, such as growth, reproduction, lactation, are shifted to support the immune response. These nutrients are required for production of white blood cells, support the inflammation process, multiplication of T and B cells, antibody synthesis, and many other immune processes. Therefore, maintaining cattle in good health will improve nutrient utilization and productivity. Similarly, cattle should always be maintained in adequate nutritional status so their immune system can work properly when needed. Some management considerations to improve the immune system of cattle are:
Nutrition – Energy and protein are required for every single process within the body, including the immune system. Energy serves as fuel for the synthesis and function of immune cells, whereas protein regulates and serves as structural component for cells and antibodies. Without proper energy and protein intake, the immune system and any immune response becomes impaired. Minerals are required for proper function of the immune components, such as pathogen recognition and antibody response. Although several minerals are important for overall body function, selenium, zinc, copper, and chromium are specifically important for the immune system and should always be offered to cattle in amounts that supply their requirements. Vitamins A, B6, B12, C, and E are also essential for proper immune function, and their roles typically overlap with those of minerals. Cattle should always receive adequate amounts of vitamins A and E in the diet, whereas supplementation of vitamins B and C are often not required because rumen bugs and body tissues, respectively, produce sufficient amounts of these vitamins.
Reducing Stress – Stressful situations also have negative effects on the immune system. Common stressors in beef operations are heat/cold stress, frequent handling, transport, and weaning. Prolonged stress, such as during extremely hot or cold tem¬peratures or after weaning, can suppress the immune response; therefore cattle would be more susceptible to diseases. Conversely, short-term stress, such as transport and handling, can activate the immune response, specifically the innate system. There¬fore, reducing the amount of stress to which cattle are exposed will benefit their health and, consequently, the productivity of the beef operation. During mandatory procedures, such as transport and weaning, cattle should be in adequate health and nutritional status to prevent further immune complications.
Vaccination – A well-planned vaccination calendar is essential for good health of the herd. Producers should work closely with a local veterinarian to prepare the vacci¬nation program ahead of time. Cattle should be in adequate health, proper nutritional status, and under no or low-stress to maximize the effectiveness of the vaccines.
Other Considerations – Newborn calves should always have adequate access to colostrum. Producers should make sure that pens, working facilities, lots, feed bunks, and water troughs are properly clean to prevent accumulation and growth of pathogens. Feeds should also be inspected for mold, excessive moisture, and toxins. Recently purchased cattle should be evaluated and, if necessary, quarantined to prevent foreign pathogens from entering the operation. Interactions between cattle, wildlife, and other livestock species should also be monitored to prevent spreading of interspecies diseases.
Conclusions: The immune system is a complex group of biological processes responsible for maintaining a healthy animal. An impaired immune system is detri-mental not only to animal well-being, but also to animal productivity. Beef producers should always seek management alternatives that enhance animal health, such as proper nutrition, low-stress management, and an adequate vaccination program. Understanding some of the basic features of the immune system will allow producers to better plan and handle these alternatives, and consequently enhance the efficiency of their operations.
References:
Abbas, A. K., and A. H. Lichtman. 2007. Cellular and Molecular Immunology, 6th edition. Saunders, Philadelphia, PA. Carroll, J. A., and N. E. Forsberg. 2007. Vet. Clin. Food. Anim. 23:105-149 Rich¬ley, E. J. 2003. University of Florida - IFAS Extension. Available at http://edis.ifas.ufl.edu/VM027.
