Implications of changing immune function through nutrition in poultry

Many nutrients are capable of modulating the immune system. The concept of nutritional immunomodulation goes beyond impairments in function associated with deficient or toxic levels of various nutrients, and involves using specific nutrients to achieve a functional goal. Using diet to alter immune function has become especially important in a production environment in which the use of growth promoting antibiotics is not legal or desired by consumers. The purpose of this review is not to give a catalog of nutrients capable of altering immune function. Rather, a brief introduction to immune function in poultry will be given, the balance between the innate and acquired responses is discussed, and examples of potential unintended consequences of nutritional immunomodulation are given. Examples of non-nutritional manipulation of poultry immunity will be given to give the reader context of how changing specific aspects of immune function can have effects on other aspects of immunity and production performance. The intention is not to suggest that nutritional immunomodulation is not possible or practical, rather, the reader will be made aware of points to consider when designing experiments or reading the literature in this area. Nutritional immunomodulation holds great promise as a means to increase poultry productivity and health, however, the implications on production traits, the danger of ascribing too much confidence in studies that report only a single or few measures of immunity may lead to changes in immune function that predispose the birds to other diseases, or decrease production characteristics. Several examples of nutritional immunomodulation have been used successfully in the poultry industry, but a greater understanding of the avian immune system will be required in order to take full advantage of this approach. (C) 2011 Elsevier B.V. All rights reserved.