|Carroll, Jeffery - Jeff Carroll|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 4/21/2010
Publication Date: 7/5/2010
Citation: Forsberg, N., Puntenney, S., Carroll, J.A. 2010. Nutrition and immunity in ruminant animals. In: Cheeke, P.R., Ellen, E.S., editors. Comparative Animal Nutrition and Metabolism. Cambridge, MA: CABI Publishing. p. 290-297. Interpretive Summary: Nutrition impacts every physiological process in the body. Hence, it should not be surprising that nutrition also has important implications to immunity and incidence of disease. While scientists have known for many years that nutrition influences immunity, only in recent years have specific mechanisms by which nutrients affect immunity become apparent. A challenge facing those with interest in the interface between nutrition and immunity is: What are the best predictors of immune status? "Immunity" is an extremely broad concept and there are literally dozens of methods available for assessing immune function. No one laboratory is capable of completing all assays of immunity and, as a result, it is often difficult to make comparisons from one study to the next. The last century focused on discovery of the nutrients and identification of their roles in biology. In the past two decades, the field of immunology has emerged as a dominant field in animal health and it is now clear that the traditional nutrients play key roles in supporting the immune system. As we learn more about signaling and control of immune function, it is likely that additional nutritional strategies will be utilized to maintain and support immune function and health of livestock species. The purpose of this chapter will be to acquaint readers with some general concepts of immunology and to review what is now known about how specific nutrients benefit the immune system of ruminant livestock.
Technical Abstract: The immune system can be generally separated into three broad components; natural immunity, innate immunity, and acquired immunity, all of which must be fully developed and functioning properly to provide adequate immunological protection. Natural and innate immunity are typically grouped together under the category of innate immunity. Therefore, for the purposes of this chapter, the immune system will be presented as two distinct "arms" which work in tandem to prevent infections. These are the "innate" immune system and the "acquired" immune system. The innate immune system, as its name implies, consists of readily-available mechanisms which "fight" the first stages of infection. This system essentially provides the first line of defense against pathogens; whether bacterial, viral, protozoal, or fungal. By providing this front line barrier, the innate system provides the time required by the acquired system to develop an antibody response against a specific pathogen. Developing the antibodies against specific pathogens requires several days to several weeks. Discussion of innate and acquired arms of the immune system separately implies that these systems function independently. However, we now know that the two arms communicate with one another and, to some extent, rely upon similar communication molecules. In the past ten years for example, we have learned that up-regulation of the innate system provides an important feed-forward system for antibody production. For example, activation of neutrophils by an invading pathogen causes neutrophils to release IL-1 beta which, in turn, stimulates the acquired system. The focus of this chapter will be on the known effect of nutrients on immunity. In non-ruminants, essential amino acids, linoleic acid, vitamin A, folic acid, vitamin B6, vitamin B12, vitamin C, vitamin E, zinc, copper, iron, and selenium (Se) affect one or more indexes of immunity. Vitamin E and zinc have received the most attention as immunostimulatory nutrients. Less is known about the nutritional regulation of immunity in ruminant livestock, but it may safely be assumed that nutrients, at the tissue level, will have similar effects on immunity in ruminants as in non-ruminants. Perhaps dietary sources of the immunostimulatory B-vitamins (B6, B12, folic acid), vitamin C, and the essential amino acids are less important in ruminants as these are either endogenously synthesized (i.e., vitamin C) or provided by a healthy microbial population (i.e., essential amino acids, B-vitamins). Research within the past decade is describing how individual nutrients affect immunity. A general mechanism by which nutrients support the immune system is via provision of antioxidants. Immune cells are characterized by high levels of reactive oxygen species (ROS) which are used, in part, to kill ingested pathogens. In addition to high ROS generation, immune cell membranes are rich in the poly-unsaturated fatty acids which are susceptible to ROS-mediated damage. Nutrients with anti-oxidant properties (carotenes, vitamin E, vitamin C, zinc, and selenium) therefore support immunity. A brief summary of how individual nutrients affect immune function in ruminants is given in this chapter. In addition to providing adequate amounts of all essential vitamins and minerals, other opportunities may exist for augmentation of immune function. Provision of microbiological fractions and probiotics in the diet has potential to support the immune system. The last century focused on discovery of the nutrients and identification of their roles in biology. More recently, the field of immunology has emerged as the dominant field in animal health and it is now clear that the nutrients play key roles in supporting the immune system. As we learn more about signaling and control of immune function, it is likely that additional nutritional strategies will be utilized