Abstract
The immune system is considered one of the most important influencing factors in improving the performance and health of poultry, and nutrition, in turn, plays an important role in balancing and strengthening the immune system. On the other hand, poultry diets are mainly formulated based on the minimum cost in order to achieve targeted performance goals, and attention to the criteria necessary to achieve ideal responses in the immune system is ignored. The increase in the world’s population and the growth in the demand for quality and healthy food have led to the fact that a 2% increase in the annual production of food is necessary, and in parallel with this increase in production, the least pressure should be placed on the environment. To achieve such goals, it is absolutely necessary to optimize feedstuff with the help of various feed additives in order to improve health, increase the bioavailability of nutrients, and improve animal performance. The main key to achieving these goals is only by having productive birds in terms of innate and acquired immunity during the breeding period. The use of feed additives in poultry nutrition can be considered as an effective solution to strengthen body immunity and a reassuring and economical proposal. Knowledge and proper understanding of the characteristics and use of additives and their effects in poultry nutrition are the goals of many researchers’ studies in recent years. Many researches have shown that feed additives can increase the bioavailability and digestibility of nutrients without negatively affecting the nutrient balance of poultry diets, and at the same time leading to the improvement of the health of the digestive system, and the quality and quantity of manufactured products have positive and promising effects. One of the beneficial and special effects that recently made the importance of a series of additives important in poultry research is their effect on the poultry immune system. The bird’s immune system is a complex network of biological structures and processes, and a decrease in performance or a slight change in any of its aspects can affect the performance and health of the bird and increase the risk of contracting various diseases. Therefore, any nutritional solution with the approach of improving physiological and immunological function can help strengthen the immune system and at the same time lead to an increase in the production capacity of poultry flocks, which can be of interest to researchers and poultry industry activists. Functional additives in poultry nutrition have many varieties. This chapter provides readers with the latest and most recent information with the aim and focus on the types of additives that were able to be effective on the poultry immune system and subsequently improve the performance and other health parameters of the poultry flock. In this chapter, an introduction is mentioned about the poultry immune system and its importance on the production performance and health of the bird. Then, the review and introduction of additives in the nutrition of poultry models and their effects on parameters related to bird health have been discussed. The feed additives investigated and effective on the body’s immune system in this season include all kinds of probiotics, prebiotics, synbiotics, medicinal plants, and phytogenic compounds, all of which are among the most valid additives. They are considered useful in poultry nutrition, which can directly or indirectly affect the poultry’s immune system.