Effects Of Yeast Polysaccharide On Growth Performance And Gastrointestinal Development Of Pre-weaning Calves

In order to investigate the effects of different levels of yeast polysaccharides on the performance,rumen fermentation parameters,gastrointestinal tract development and digestive enzyme activities,rumen microflora,and immune related gene expression of pre-weaning calves.Fifty-six healthy Holstein calves with similar body weight were selected and allotted randomly to four groups with fourteen calves?six heifers+eight bulls?each group.Calves in group??YP1?were fed the basis dietary,and the group II?YP2?,group III?YP3?,and group IV?YP4?were added 1,2,and 3g/d/head of yeast polysaccharides on the basis diet.The whole experiment lasted for 60 d.The results showed that:?1?The ADG of calves in group?and?was significantly higher than that in group I?P<0.05?.DMI of calves in group?was the highest.The apparent digestibility of DM,CP,EE,NDF and ADF of calves in group?,?,?was significantly higher than calves in group I?P<0.05?.The diarrhea rate and diarrhea frequency of the calves in group?,?and?were lower than those in the group I.The concentrations of serum ALP,LZM,T-AOC and IgA in group III calves were significantly higher than those in group I?P<0.05?.The concentration of serum MDA in the group?was significantly decreased compared with the group I.?2?During the whole trial period,there was no significant difference in rumen fluid pH,butyric acid concentration and acetate:propionate ratio among the groups?P>0.05?.The acetic acid concentration of group?was significantly higher than that in group I?P<0.01?,and there was no significant difference for the concentration of propionic acid among the four groups?P>0.05?.The TVFA concentration in group?,?and?were significantly higher than that in group I?P<0.05?,and the group?had the highest TVFA concentration.The NH₃-N concentration had no significant difference among the four groups?P>0.05?,the yield of MCP in group?was significantly higher than that in other groups?P<0.05?.?3?The result indicated that the amylase,pepsin,lipase and carboxymethyl cellulase activity in the rumen of group III was significantly higher than that in group I?P<0.05?.The activity of amylase,trypsin,lipase and carboxymethyl cellulase in the middle of duodenum and middle of jejunum in group III was significantly higher than that in group I?P<0.05?.The rumen papillae length,width and mucosal thickness of calves in group III was significantly higher than that in group I?P<0.05?.The villus height of duodenum and jejunum in group III were significantly higher than that in group I?P<0.05?,crypt depth was significantly lower than that in group I?P<0.05?.The V/C value in group III was significantly higher than the other groups?P<0.05?.?4?With the increase doses of yeast polysaccaride,the alpha diversity index increased significantly,that the group YP3 and YP4 were significantly higher than group YP1?P<0.05?.According to the relative abundance of species composition in bacterial flora in phylum level,Firmicutes,Bacteroidetes and Proteobacteria were the predominant phylums.There was no significant difference in the proportion of Bacteroidetes between each group?P>0.05?.The ratio of Firmicutes,Proteobacteria,Tenericutes and Fibrobacteres was significantly higher in the group YP3 than in the group YP1?P<0.05?.Analyzed the relative abundance of the species composition of the bacterial flora of gastric juice in genus,Prewotella was the dominant genus.The relative abundance of Prevotella,Lachnospraceae-NK3A20-group,Rikenellacese-RC9-gut-group,Ruminnococcus-1,Fibrobacter,Succinivibrio,Selenomonas,Succiniclasticu in the group YP3 were significantly higher than that in group YP1?P<0.05?.?5?The mRNA expression of TXN,SOD1 and LYZ in liver tissues were significantly higher in group III than in group I?P<0.01?,and the expression of PRDX1was significantly up-regulated.The expression of TLR4 in group?and III was significantly higher than that in group I?P<0.01?.The expression of TLR4 was up-regulated?P<0.05?.The expression of TNF,IL-1?and IL-10 was significantly increased in group III and group IV,higher than these in group I?P<0.01?.The mRNA expression of LYZ was higher in group?than in group I?P<0.05?.In conclusion,in this trial,adding yeast polysaccaride to the diet for pre-weaning calves can increase the growth performance,improve the immunity of calves,enhance the utilization of ammonia and protein in the rumen,promote the development of gastrointestinal morphology,and improve the digestive enzyme activity,increase the relative abundance of the dominant flora in the rumen fluid of calves,promote the expression of immune-related genes and improve the body immune response.The appropriate amount of yeast polysaccaride for pre-weaning calves is 2g/d/head.