Optimization Of Extraction Process Of Polysaccharides From Shenmai Fibrous Root And Its Prevention And Treatment Of Diarrhea In Weaned Rabbits

Post-weaned rabbits are susceptible to various intestinal diseases in the veterinary industry,predominantly diarrhea,which may ultimately result in the reduction of disease resistance and the increase of mortality.Natural plant-derived polysaccharides have been found to possess innate growth-promoting and immune-stimulating properties.In the current study,Panax ginseng fibrous roots with nutritive effects and Ophiopogon japonicus fibrous roots with yin-nourishing effects mixed in a 1:1 ratio(Shenmai fibrous roots)were selected as raw materials to extract polysaccharide-based components using the hot-water extraction method.The extraction process was optimized,and the obtained water extract of Shenmai fibrous roots was concentrated and precipitated with ethanol.The precipitate was further mixed with auxiliary ingredients to prepare granules,which were subsequently supplemented in the diet of weaned rabbits to evaluate the therapeutic efficacy of Shenmai fibrous root polysaccharide granules against diarrhea on post-weaned rabbits.1.The optimal extraction process of polysaccharides from Shenmai fibrous roots using hot-water extraction method.The extraction temperature(80-100 ℃),extraction liquid-solid ratio(15-55 m L/g),and extraction time(0.5-2.5 h)were evaluated separately in single-factor experiments,with the yield of polysaccharides serving as the evaluation indicator.An orthogonal experiment with three-factors-three-level design was conducted to obtain the optimal extraction condition.The results indicated that the extraction temperature was the most significant factor influencing the yield of polysaccharides from Shenmai fibrous roots,followed by the extraction time and the ratio of extraction materials to liquid.The optimum extraction condition was shown as following: extraction temperature of 100 ℃,a solvent medicinal material ratio of 35:1 m L/g,and an extraction time of 2.5 h.Experimental verification yielded a polysaccharide yield of 29.62%(w/w).A large batch of Shenmai fibrous roots was then extracted with the same method,and all the water extract was concentrated and precipitated with ethanol.The precipitate was mixed with auxiliary ingredients to produce granules which were determined and met the pharmacopoeia indicators for size,moisture content,meltability,and drying weight loss.2.Effects of Shenmai fibrous root polysaccharide granules on growth performance,serum biochemistry,and immune function of weaned New Zealand meat rabbits: A total of180 weaned rabbits,aged 35 days,were selected for this study.After a 7-day of environmental adaption,the rabbits were randomly assigned into five groups,with 12 replicates in each group and three rabbits in each replicate.The rabbits in the control group were fed with 302 meat rabbit formula feeding diet,while those in the antibiotic group was supplemented with 0.25% antibiotic enrofloxacin in the feeding diet.The remaining three groups were administrated with the low(0.25%),medium(0.5%),and high dosage(1%)of Shenmai fibrous root polysaccharide granules in the feeding diet.All administration lasted for 14 d in total,during which the growth performance,serum biochemistry,and immune function of the weaned rabbits were evaluated.The results demonstrated that:(1)the supplementation of Shenmai fibrous root polysaccharide granules in the diet significantly increased the average daily weight gain of weaned rabbits and reduced the feed/gain ratio(P<0.05);(2)the supplementation of Shenmai fibrous root polysaccharide granules in the diet reduced the incidence of diarrhea and mortality rates of weaned rabbits,which was better than that of the antibiotic group;(3)the supplementation of Shenmai fibrous root polysaccharide granules in the diet significantly increased the levels of GLO and ALP in the serum of weaned rabbits(P<0.05),while significantly reduced the levels of TC and TG(P<0.05);(4)the supplementation of Shenmai fibrous root polysaccharide granules in the diet increased the thymus index and spleen index of weaned rabbits(P<0.05),increased the content of Ig G and Ig M(P<0.05),and reduced IL-6 and TNF-α contents in the serum(P<0.05),which were better than those of the antibiotic group.The experimental findings suggested that the inclusion of Shenmai fibrous root polysaccharide granules in the diet has a growth-promoting effect on meat rabbits by improving their nutritional status and immune function,thereby decreasing diarrhea and mortality rates.3.In this study,the effects of Shenmai fibrous root polysaccharide granules on immunoglobulin content,oxidative stress indicators,and intestinal barrier function-related genes in different intestinal segments of weaned rabbits were investigated.The content of intestinal secretory immunoglobulin was measured using the Elisa reagent kit,while the biochemical reagent kit was used to measure the content of intestinal antioxidant enzymes.The m RNA expression of intestinal barrier-related genes was detected using RT-PCR.The results indicated that the supplementation of Shenmai fibrous root polysaccharide granules in the feeding diet led to significantly increase of the level of SIg A in the duodenum,as well as the contents of SOD,T-AOC,and CAT in the intestines(P<0.05);additionally,the content of MDA was significantly reduced(P<0.05).The relative expression levels of intestinal barrier genes ZO-1,JAM-2,occludin,and claudin of weaned rabbits were significantly increased(P<0.05)after supplemented with Shenmai fibrous root polysaccharide granules in the diet.Furthermore,a significant reduction in the proinflammatory factor IL-1β in the intestine was observed,while the gene expression level of anti-inflammatory factor IL-10 in the intestine was increased(P<0.05).These findings indicated that the supplementation of Shenmai fibrous root polysaccharide granules in the feeding diet could enhance the intestinal antioxidant stress capacity and improve the intestinal physical and immune barriers of the weaned rabbits.As a result,this intervention could probably maintain intestinal health and reduce diarrhea in weaned rabbits.4.This study aimed to investigate the effect of Shenmai fibrous root polysaccharide granules on the cecal microbiota of weaned rabbits.The changes on the microbiota composition in the cecal contents of the weaned rabbits were analyzed using 16 s r DNA sequencing technology.The results indicated that the supplementation of Shenmai fibrous root polysaccharide granules in the feeding diet increased the number of OTUs in the cecum,with a unique 257 OTUs in the control group,364 in the antibiotic group,354 in the 0.25% dosage group,595 in the 0.5% dosage group,and 580 in the 1% dosage group.Moreover,the supplementation of Shenmai fibrous root polysaccharide granules significantly increased the abundance of Bacteroideta at the level of phylum(P<0.05),while the relative abundance of Proteobacteria was significantly reduced(P<0.05).The relative abundance of beneficial bacteria at the genus level,such as the Rikenellaceae,were also increased(P<0.05),and the relative abundance of harmful bacteria,such as the Ralstonia and Porphyromonas were reduced(P<0.05).In addition,the observed level of cecal microbiota specifications index and chao1 index(P<0.05)were significantly increased by the supplementation of Shenmai fibrous root polysaccharide granules,thereby enhancing the α-diversity of the intestinal microbiota.In the PCOA diagram,the microbial community disorder caused by weaning stress reduced as well.These findings indicate that the supplementation of Shenmai fibrous root polysaccharide granules in the feeding diet could increase the diversity and abundance of the cecal microbiota in weaned rabbits,reduce the disturbance of the microbiota caused by weanling stress,and potentially treated diarrhea in weaned rabbits.In this study,the water-extraction process of Shenmai fibrous root with polysaccharides as the main component was optimized.The polysaccharide content reached to be the highest when the extraction was performed at a temperature of 100 ℃,a solvent medicinal material ratio of 35:1 m L/g,and an extraction time of 2.5 h.The water extract was then concentrated and precipitated,and prepared into granules as a supplement in the diet.Subsequently,the supplementation of these granules in the diet of rabbits was shown to be able to enhance the growth performance,reduce diarrhea and mortality rates,improve the immune function,enhance the antioxidant stress ability,and improve the intestinal barrier function.Moreover,it could increase the abundance and diversity of the cecal microbiota composition.The findings suggest that Shenmai fibrous root polysaccharide granules has a potential to replace antibiotics as feeding additives in the practical veterinary production.