# \(\beta\)-Glucans from Yeast--Immunomodulators from Novel Waste Resources
## 8 Administration to Livestock  
The European Union outlawed antibiotics as feed additives in 2006, demanding rapid research and development of antibiotic alternatives [111]. With several studies showing \(\beta\)-glucan immunostimulant properties, and the restriction on growth and immunity-promoting antibiotics, they are now being fed to farm animals [112; 113]. Antibiotics were routinely used to protect livestock from illness and to stimulate appetites. Resistance to antibiotics and antibiotic residues in food products are frequent effects of antibiotic usage. As a result, there is a persistent need for antibiotic replacement. \(\beta\)-glucan is one such replacement possibility [114].  
Vaccinating all animals is time-consuming and costly, so one of the critical benefits of \(\beta\)-glucan is that it may be provided orally and elicit the same effects as if it was administered via another method.  
The effects of \(S\). _cerevisiae_ yeast on the cell walls of _Salmonella_ and _Campylobacter_ infected turkeys were studied in-vivo. Fresh faeces were taken for _Salmonella_ and _Campylobacter_ counts as well as iliac tissue for histomorphological analysis. The group administered yeast cell wall had lower levels of Salmonella and larger villus surface ratios than the control group [115]. The ileum of broilers fed yeast cell walls enhanced _Lactobacillus_ and _Biftobacterium_ while decreasing _Clostridium perfingens_[116].  
To examine the effect of sulphated yeast \(\beta\)-glucan on immunosuppression, 11-day-old hens were randomly allocated to five groups and given cyclophosphamide once daily for three consecutive days, except for the standard control group. Cyclophosphamide was administered to induce immunosuppression. At 14 days, chickens in three experimental groups received oral sulphated yeast \(\beta\)-glucan from \(S\). _cerevisiae_ in three doses for 14 days. At 4 mg/kg, \(\beta\)-glucan significantly increased the bursa index, I.F.N-\(\gamma\) and IL-6 concentrations, decreased TGF-\(\beta\)1 concentration, and promoted lymphocyte proliferation; it also considerably decreased bursa histopathological changes, and improved gut _Bifidobacterium_ and _Lactobacillus_ populations in chicken caecal digesta compared to the model control group. This demonstrated that G.S.C. might successfully reverse immunosuppression and maintain a healthy gut microbiome [117].  
By producing a healthy gut microbiome and encouraging gut development, yeast-derived products have been demonstrated to boost body weight, body weight growth, and feed conversion ratio in broiler diets. In another study, the presence of \(\beta\)-glucan dramatically enhanced the number of goblet cells in chick jejunum, indicating that \(\beta\)-glucan supports gut health. Other studies, on the other hand, discovered no difference [118; 119; 120; 121]. A study by [PERSON] et al. (2019) administered yeast \(\beta\)-glucan to investigate growth performance, immunity, and intestinal morphology in chicks. Results demonstrated that growth performances increased after administration. However, the mechanisms by which these effects were achieved are not fully elucidated. White blood cells and lymphocytes were increased in chicks fed the \(\beta\)-glucan diet. These cells are crucial for defence against infection and help restore damaged tissues in the body [123].