Figure 1 — β-glucans in the cell wall of yeast.


Cell membrane & cell wall composition Mannoproteins


intestinal clearance of E. coli and Salmonella through increased expression of jejunal tight junction proteins.


Cell wall


β-1,6-glucan β-1,3-glucan


Chitin Cell membrane Ergosterol Membrane protein


increased immune response. And moreover, they increase goblet cell numbers and villus height in the ileum, as well as restoring villus damage/loss by Salmonella species. Increased villus height of the jejunum mucosa of chickens raises the total surface area for nutrient absorption. The goblet cells of the gastrointestinal tract are specialised cells able to produce and secrete mucus. Goblet cells in the intestinal mucosa secrete mucus, which provides the first line of defence against intestinal injury. On the other hand, β-glucans reduce the severity of intestinal lacerations and inflammation in broilers suffering from Eimeria/coccidia infection. In addition to its role in nutrient digestion and absorption, the lining of the digestive tract acts as an effective barrier against pathogen invasion. The lining of the digestive tract provides the innate defence barrier against most intestinal pathogens. The integrity of the digestive system is maintained by the family of proteins called tight junctions. Tight junction proteins form a solid barrier from pathogen invasion. Dietary supplementation with β-glucans to poultry increase the


Figure 2 — Summary of the activities exerted by β-glucans. Bacterial removal


Villus height +


Number of goblet cells


+ +


Crypt depth Tight Junctions


+ + +/- Spleen weight


Modulation of immune response


+ IL-2 production


This article is based on the research paper ‘Review: β-glucans as Effective Antibiotic Alternatives in Poultry’, written by B. Schwartz and V. Vetvicka. The full paper can be accessed in the journal Molecules.


28 ▶ ANTIBIOTIC REDUCTION | DECEMBER 2021 + β -glucans + Weight


Improves growth Supplementing poultry diets with β-glucans improves growth performance (weight gain and FCR) and meat quality and stimulate both specific and non-specific immune responses. β-glucans use various mechanisms to improve the growth performance of birds: They are active against intestinal pathogens such as E. coli and Salmonella via the regulation of intestinal barriers through stimulation of tight junction proteins and phagocytosis, thus inhibiting major pathogen invasion in a prebiotic way. β-glucans also enhance goblet cell number and villus height in the ileum, increasing the total surface area for nutrient absorption (Figure 2). Goblet cells are cellular structures responsible for maintaining the integrity of the mucous protective layers for effective removal of enteric pathogens. And under stressful conditions, they offer a protective shield against stress, sparing energy for normal growth.


Improves efficacy of vaccines β-glucans show amelioration of immunosuppression and increased efficacy of the Newcastle disease vaccine in chickens. Black yeast-derived β-glucans are shown to enhance the immune response to the H5N1 and H5N2 vaccines tested in mice and poultry. Although the exact mechanisms for these effects are not clear, the additive effects might be attributed to all the immunomodulatory effects of β-glucans.


Are all β-glucans the same? The origin, molecular structure and purity of β-glucans differ, resulting in differences in efficacy. That is why not all beta glu- cans are the same. When comparing fungal and yeast glucans to barley β-glucans, fungal and yeast β-glucans have side chains linked at the 1 and 6 carbon atoms. In contrast, barley β-glucans have the glucose molecules linked at the 1 and 4 car- bon atoms with some linkages between the 1 and 3 carbon at- oms. When comparing fungal and yeast β-glucans, fungal β-glucans have shorter side chains giving them a branched structure. The structure of these glycosidic linkages affects the functionality of β-glucan molecules. Non-purified yeast glu- cans usually contain mannoproteins which are part of the cell wall. However, besides the differences, research findings show that owing to their immunomodulatory and promo- tion of intestinal integrity, β-glucans are potential growth promoters and antibiotic alternatives in poultry production.


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