Yeast β -Glucans in Poultry Farming

Bacterial infections in poultry industry are a crucial problem for both poultry health and productivity. Over the years, antibiotics have been widely used to protect poultry from the bacterial infections and improve growth performance and production. However, antibiotic residues and antibiotics resistance of pathogenic bacteria are becoming more and more serious, which is an important concern for consumers [1]. As a result, several antibiotics have been withdrawn from the list available to poultry farming industry. To maintain poultry health and efficient production, feed manufacturers and research communities have proposed a few alternatives to antibiotics. There has been increased interest in “natural” feed additives that can stimulate the immune system of poultry.

Among all the “natural” immunostimulants, perhaps polysaccharides are the most attracting. While among the various polysaccharide immunostimulants, β-glucans are undoubtedly a star [2]. β-glucans comprise a very big family of polysaccharides in which glucose molecules – as the only building block – are linked together by β-linkages. β-glucans are structural components of cell walls in many different sources including bacteria, fungi, algae, and yeast. They are also found in cereals (such as barley, oats and rye) and some plants. The structure of β-glucans, however, vary among the different sources and account for the differences in their physiological function [3]. In general, we can summary the types of β-glucan linkages usually found in different sources in Table 1.

Table 1:Types of β-glucan linkages usually found in different sources.

β-glucans from yeast and fungi, i.e. β-(1→3) (1→6) glucans with branches, have been found to possess beneficial effects as supplements [4] (Figure 1). In contrast, β-glucans from cereals, i.e. β-(1→3) (1→4) glucans are seldom used in feed due to their detrimental effects on poultry health and performance.

β-glucans from yeast and fungi are both effective. However, perhaps due to the manufacturing cost, yeast β-glucans are much more widely used in applications compared to fungi β-glucans. After decades of studies, the health benefits of yeast β-glucans have been well established in humans in the meantime. A great deal of evidence demonstrates similar benefits in poultry farming [5].

Yeast β-glucans increase resistance against pathogens

The immune system is the host defense system that protects it against diseases. Yeast β-glucans play an important role in the activation of both innate and adaptive immune systems. They activate macrophages, a key component of the non-specific (innate) immune system. Dietary supplement with yeast β-glucans has been shown to increase the macrophage phagocytic activity and make lymphoid organs bigger [1, 6].

Figure 1:The primary structure of yeast β-(1→3)(1→6) glucan.

Yeast β-glucans boost the immune system of neonate chickens

The first days after hatching, young chickens are highly susceptible to infections by opportunistic pathogens. Yeast β-glucans in the diet of neonate chicken can challenge with Salmonella, resulting in a significant protection against this pathogen [7].

Yeast β-glucans reduce food poisoning by Salmonella

Salmonella is one of the four key global causes of diarrheal diseases and results in over 250,000 human deaths annually [8]. Poultry is a common source of Salmonella. Feeding broiler chickens with feed containing yeast β-glucans showed a significant reduction in the Salmonella counts of different organs [9, 10].

Yeast β-glucans improve poultry performance

I. Bacterial infections are not only an important concern for poultry health, but also for poultry productivity. There are many reports in this regard. For example, Supplementation of chicken diets with yeast β-glucans can improve growth performance, such as average daily gain and feed conversion ratio. The poultry performance benefits of yeast β-glucans were especially pronounced when the flocks were raised under “dirty” or challenging trial conditions, resulting in lower mortality [11, 12].

1. Ding B, Zheng J, Wang X, Zhang L, Sun D, et al. (2019) Effects of dietary yeast beta-1,3-1,6-glucan on growth performance, intestinal morphology and chosen immunity parameters changes in Haidong chicks. AJAS 32(10): 1558-1564.
2. Shi L (2016) Bioactivities, isolation and purification methods of polysaccharides from natural products: A review. Int J Biol Macromol 92: 37-48.
3. Jacob JP, Pescatore AJ (2014) Barley β-glucan in poultry diets. Ann Transl Med 2(2): 20.
4. Zhu F, Du B, Xu B (2016) A critical review on production and industrial applications of beta-glucans. Food Hydrocoll 52: 275-288.
5. Jacob J, Pescatore A (2017) Glucans and the poultry immune system. Am J Immunol 13(1): 45-49.
6. Guo Y, Ali RA, Qureshi MA (2003) The influence of beta-glucan on immune responses in broiler chicks. Immunopharmacol Immunotoxicol 25(3): 461-472.
7. Lowry VK, Farnell MB, Ferro PJ, Swaggerty CL, Bahl A (2005) Purified beta-glucan as an abiotic feed additive up-regulates the innate immune response in immature chickens against Salmonella enterica serovar Enteritidis. Int J Food Microbiol 98(3): 309-318.
8. GBD 2015 Mortality and Causes of Death Collaborators (2016) Global, Regional, and national life expectancy, all-cause mortality, and cause-specific mortality for 249 causes of death, 1980-2015: a systematic analysis for the Global Burden of Disease Study 2015. The Lancet 388(10053): 1459-1544.
9. Shao Y, Wang Z, Tian X, Guo Y, Zhang H (2016) Yeast β-d-glucans induced antimicrobial peptide expressions against Salmonella infection in broiler chickens. Int J Biol Macromol 85: 573-584.
10. Revolledo L, Ferreira CS, Ferreira AJ (2009) Prevention of Salmonella typhimurium colonization and organ invasion by combination treatment in broiler chicks. Poult Sci 88(4): 734-743.
11. Tian X, Shao Y, Wang Z, Guo Y (2016) Effects of dietary yeast β-glucan supplementation on growth performance, gut morphology, intestinal Clostridium perfringens population and immune response of broiler chickens challenged with necrotic enteritis. Anim Feed Sci Technol 215: 144-155.
12. Huff GR, Huff WE, Rath NC, Tellez G (2006) Limited treatment with beta-1,3/1,6-glucan improves production values of broiler chickens challenged with Escherichia coli. Poult Sci 85(4): 613-618.