Interest in veterinary nutrition has grown dramatically over the past 20 years, both for treatment of animals with short-term illness, as well as for long-term treatment of chronic conditions. Many evidences-based on improvements in diet have been identified through human clinical nutrition work, but now are becoming available in companion animal clinical nutrition. Nutrition plays a complex and controversial role in disease prevention in both humans and animals.

We need to think about applying new understanding of genomics of the animal, which may permit an understanding as to individual variability in nutritional response for the future optimum productivity.

Applying comparative nutrition information appropriately is a challenge because evaluating nutritional impact of certain nutrients on some disease situations. Our growing understanding of nutrition-disease linkages also is widening the definition of disease. Thus feeding to prevent disease encompasses both positive contribution of nutrition to optimise all metabolic functions - and particularly the immune system - as well as the avoidance or minimisation of intake of toxic or undesirable substances in feed. A nutrient requirement for a farm animal may differ according to a measurable performance objective - for example, optimum growth rate, food conversion efficiency or bone mineral contents. We should now apply this approach to animal nutrition and disease prevention. This approach decries excessive supplementation, rather, it follows the concept of "optimum nutrition" or targeted nutraceutical application. This approach seeks to provide integrated support to strengthen the physiological and biochemical systems of the animal in order to permit the animal's own metabolic processes to maximise the benefit. The optimum nutrition approach recognises the use of amino acids, for example as biological response modifiers, rather than as compounds to meet a 'single value' nutrient requirement. Further, this approach avoids using supplemental levels of nutrients and ingredients for direct pharmacological effect, but rather seeks to balance and encourage the body's own systems. Chief among these body systems is the immune system.

Immune System - A Focus
FEEDING to maintain immune competence throughout the life is the key to long-term health in animals. The immune system is a complex array of cells, tissues and signaling chemicals that work together to protect the body against foreign substances. The body's largest immune organ is the lymphoid tissue, which spans the entire intestine. The intestinal mucosal epithelium is the first line of defence, acting both as a barrier and as a source of secretory immunoglobulin IgA. This tissue is susceptible to damage and degraded immune function, particularly during times of stress, such as dietary change, high production level and age related changes in the immune system itself. One of the key priorities of optimal nutrition is to support this tissue during times of stress and to enhance the 'global immune status of animal.

In a latent, unstimulated condition, the immune system contains some of the least nutritionally demanding cells in the body. However, when stimulated, it probably generates the greatest possible demand for nutrients. At the same time, the resulting metabolic disturbance causes a depression in appetite.



Feed ingredients that have been shown to be beneficial include- Nucleotides, B-glucans, and direct immunglobulins (such as direct from colostrum). Other dietary components can be beneficial by regulating the production of pro-inflammatory cytokines. Anti-inflammatory regulators, such as polyunsaturated fatty acids (PUFAs) can be beneficial, as can supplemental vitamin E and regulators of energy intake. However, it is important to remember that general nutritional adequacy is a key factor in the maintenance of an optimum immune system.

During Disease Challenge - Role of Nutrients
The elevated levels of pro-inflammatory cytokines during disease challenge redirect nutrients from anabolic pathways to those that bolster the defence mechanisms. This repartitioning of nutrient causes increased protein turnover, resulting for example in elevated body temperature and basal metabolic rate. Because this repartitioning affects almost every nutrient, an immune challenge results in overall changes to metabolism and behavior. Some of these effects are the result of the immune response itself - for example, generation of reactive oxygen species and protease - rather than the pathology of the disease.

Repartitioning is also used by the immune system to alter the bioavailability of nutrients, for example to restrict nutrients from an invading pathogen - as with the nutrient iron. Due to changes in the rate at which they are metabolized, some nutrients increase in availability during a disease challenge, others become less available due to damage to the intestinal structure. They even become unavailable due to liver or kidney damage; hence the need to have an appropriate feed formulation or supplementation of some of the important ingredients prior to any disease challenge is necessary, so as to build up body store of key nutrients in a form that can be successfully utilised. Alternatively a suitably designed supplementation to administered immediately on challenge by a disease.

Nutrient Support
In order to support immune function nutrient repartitioning, we can increase the body's reserves of key nutrients prior to any disease challenge or vaccination procedure. Once a challenge has occurred, however such feeding may be too late to be of benefit, and may even be detrimental to the immune defence capability. Appropriately designed nutrition can support the immune system in several ways, including:

Optimising the nutritional status of the developing embryo, which can aid in the development of the immune system and enhance the long-term well being of the animals - PROTOFACE is well designed to combat the challenges whether bacterial or viral by enhancing the immune-competence of the body Providing substrates for the proliferation of immune cells and 'effector' molecules, Avoiding nutrient deficiencies and excesses, which impact both the animal and invading pathogen, because a pathogen relies on the host for nutrients, and Controlling effects on the endocrine system, thus modulating the magnitude, duration or type of immune response.