Chinese natural medicinal products as feed supplements have been used as growth and health promoters in farm animals in China for centuries. A current estimation of the number of Chinese natural medicines ranges between 6,000 and 8,000, of which less than 5% has immuno-active properties. Most of these medicinal products originate from plants. Polysaccharides are considered to be the most important components, which may act as immune enhancers or immuno-modulators. The relationship between polysaccharide structure and bio-activity is, however, not well understood. In this review, immune activities of the polysaccharides from two mushrooms, Lentinus edodes and Tremella fuciformis, and a herb, Astragalus membranaceus radix, are reported, based on studies in chickens, mice, rats and humans. It can be concluded from these studies that polysaccharides derived from these products can play important roles in: (1) stimulating the growth of immune organs such as spleen, thymus and bursa; (2) increasing the number and activities of many interdependent cell types such as T, B lymphocytes, macrophages, natural killer (NK) cells and lymphokine-activated killer (LAK) cells; (3) enhancing T-cell mediated immune response, such as an increased rate of T-lymphocyte transformation and proliferation; (4) enhancing humoral immune response, such as spleen and serum antibody production, the number of haemolytic plague forming cells (PFC) and haemolysin production and (5) inducing secretion and production of cytokines and complements of T-cells and NK cells.
Today's poultry producers are confronted by numerous prophylactic techniques to prevent diseases. The immuno-active polysaccharides from mushrooms and herbs might be good candidates as health promoting feed additives in poultry diets. Further studies are needed to investigate the effects of such bioactive components to improve productive performance in chicken and to elucidate the possible modes of action related to the gut ecosystem and the immune response.
