Research On Regulatory Activities Of Yeast Polysaccharides (?-glucan And Mannan Oligosaccharides) On Diseases Of Farm Animals

Fungal polysaccharides are known for their immunomodulatory activities to animal health.Yeast cell wall is comprised for ?-glucan and mannan oligosaccharides(MOS)and is becoming one of the most popular animal feed additives as antibiotics alternative for use to boost immune function and for removal of mycotoxins.Aspergillus fumigatus is one of pathogenic fungi that poses severe challenge to farm animals suffering immunosuppression and environmental stresses and is often the major cause of systemic fungal infections and consequent diseases such as respiratory infections and abortion.Early detection of A.fumigatus is critical in feed quality monitoring and disease control,however,effective and fast approach of such early detection is not ready yet.In this study,firstly,HPLC assays were established and the two major components in the yeast cell wall,?-glucan and MOS were quantitatively examined.Results show that in the yeast cell wall extract we used there are 23.9% ?-glucan and 21.3% MOS.Next,a novel quantitative RT-PCR based technology for detection of A.fumigatus was set up with sensitivity to detect A.fumigatus at a level as low as 10 fg.This rapid and sensitive A.fumigatus detection method established may facilitate early diagnosis and prevention of invasive aspergillosis(IA)in farm animals.Furthermore,by applying this PCR assay,a survey was conducted to examine the A.fumigatus contamination in a sizable dairy feed samples collected from farms cross China,then the fungal burden in dairy cows in the farms were examined as well.The data shows that A.fumigatus contamination is very prevalent in these Chinese dairy farms.59% of the samples were tested positive containing 158 to 1,300,000 pathogenic spores per gram of the feed samples.This result urges the importance in control of A.fumigatus in Chinese dairy farms.Solutions to such fungal pathogen contamination may not only improve animal performance in China,it also might help relieve the rising public food safety concerns too.It is also found that intestinal bleeding in animals might caused by A.fumigatus contamination due to their statistical significant correlation.Using a sheep model of which immune system is compromised with administration of dexamethasone,it is determined that the YCW polysaccharides was able to recover immune function.It is observed that the addition of YCW in animal feed was able to improve the level of L-selectin and IL-1? in blood.The mechanism behind the scene might be,the YCW polysaccharides enhance neutrophil function,inhibit the apoptosis of immune cells,help neutrophil to effectively enter the site of infection and kill pathogens.Moreover,gene profiling was employed to identify the gene expression pattern altered by YCW polysaccharides.The result shows that most of the genes that experienced more than 10 folds change are those involved in immune response in animal,including IL-4R-?,IL-1?,FGF etc..An in vivo study was conducted using tumor bearing mouse model later to examine wether YCW polysaccharides has the anticancer activity or not.It is found that compared to the controls,mice that was given YCW polysaccharides had larger thymes and spleens and the tumors grew slower,indicating the immune systems had been benifited by the added YCW polysaccharides in their diets.The serum level of the proteins that are often used as immune function indicators were examined as well,they are TNF-??CRP?IFN-?,IL-6.The results are consistent with the finding of in vitro anticancer assays using cell lines of SKOV-3 and MCF-7.As an reality check,YCW polysaccharides were applied in two different field animal farmings,chicks and pigs,locating in Jilin and Zhejiang provinces,respectively.In chicks study,with the addtion of YCW polysaccharides,the experimental group had better flock performance significantly gaining more weight and better vaccination result.In pigs study,YCW polysaccharides prevented sows from A.fumigatus infection caused diarrhea,stillbirth and miscarriage,and the piglet survival rate and weaning weight were significantly improved.In both field studies,YCW dietary supplement significantly elevated the expression of CD62L(P< 0.01)and IL-1?(P<0.05).The serum level of cytokines such as anti-tumor factor(TNF)-?,interleukin(IFN)-?,MIP-1?,CD4+ / CD8+,showed significantly improved when compared to controls.