| High-concentrate diet has always been used to meet the milk production in dairy farm.However,overfeeding concentrate diet will make less content of physical effective fiber in diet and reduce the rumen fermentation,resulting in the accumulation of volatile fatty acids in the rumen.Then,decreased rumen pH value will lead to the subacute ruminal acidosis(SARA).Besides,low rumen pH can cause the proliferation and disintegration of gram-negative bacteria in the rumen,and release a large number of free LPS.When excess LPS goes into the liver through the portal vein,it will cause inflammatory injury of the liver and stimulate the liver to secret acute phase proteins,which trigger systemic acute phase response.Therefore,this paper focused on the study of the inflammatory injury in the liver caused by high-concentrate diet feeding in dairy cows,as well as the manipulation of SARA.1.Inflammatory injury in the liver caused by high-concentrate diet feeding in dairy cowsThe high-concentrate diet reduces the pH value in rumen,and causes the release of LPS because of the disintegration of gram-negative bacteria.LPS enters the liver through the portal vein,which can affect the liver's nutritional metabolism and immune function.In this study,8 lactating Holstein cows were used to install the rumen fistula and hepatic vein,portal vein as well as jugular vein cannulas.Cows were separated into two groups after feeding with 40%concentrate diet for 4weeks,control group continued with 40%concentrate diet and treatment group fed with 60%concentrate diet(n=4).8 weeks later,rumen fluid,blood samples from hepatic vein,portal vein and jugular vein,as well as liver tissue samples were collected.Results showed that,rumen pH dropped below 5.6 and lasted for more than 3 h/d in treatment group while control group did not,means SARA was induced in treatment group.Inflammatory cells infiltration and liver cells injury ballooning were observed in treatment group compared to control group.Meanwhile,the mRNA relative expression of immune-related genes TRAF3,TRAF6,TBK,ERK,p38 and IL-6 as well as the phosphorylation of proteins NF-?B,p38 in the liver were significantly higher in treatment group than control group(p<0.05).Besides,the concentration of pro-inflammatory cytokines IL-1??IL-6 and TNF-? in peripheral blood were significantly higher in treatment group compared to control group(p<0.01).In conclusion,high-concentrate diet feeding could accumulate LPS in the liver of dairy cows,activate NF-?B,p38 MAPK signaling pathway,promote the release of pro-inflammatory cytokines,and cause inflammatory damage to the liver of dairy cows2.The effect of high-concentrate feeding on rumen microbiota in dairy cowsThe increase of concentrate content could decrease the content of fiber in the diet,and then affect the microbiota in the rumen.12 lactating Holstein cows were used to install the rumen fistula and portal vein cannula were separated into two groups after feeding with 40%concentrate diet for 4weeks,high-concentrate group(HC)continued with 40%concentrate diet and low-concentrate group(LC)fed with 60%concentrate diet(n=6).8 weeks later,rumen content was collected.Rumen LPS were detected and 16S rRNA were used to carry out high throughput sequencing for microbiome analyzing.Turns out,the concentration of rumen LPS were significantly higher in HC compared to LC(p<0.01).The relative abundance of Bacteroidetes were decreased in HC compared to LC,Hallella(p<0.01),Prevotella(p=0.04)and Unclassified Prevotellaceae(p=0.01)in Bacteroidetes were obviously lower in HC compared to LC group,while the relative abundance of Firmicutes were higher in HC than LC,Lachnospiraceae(p<0.01),Ruminococcus(p=0.02)and Clostridia(p=0.04)in Firmicutes were higher in HC than LC group.Howerver,Succiniclasticum(p<0.01)in Firmicutes were lower in HC than LC.The results showed that high-concentrate diet reduced the relative abundance of cellulolytic bacteria,and allowed the proliferation of Firmicutes and other opportunistic bacteria,which led to the increase of LPS concentration in the rumen.3.Effects of dietary changes on SARA in dairy goatsChanging the size of the dietary grains can alter the rumen fermentation and reduce the risk of ruminal diseases in ruminants when fed a high-grain diet.8 mid-lactating dairy goats fixed with rumen fistula,hepatic vein,portal vein and jugular vein cannulas were randomly assigned into two groups,control group fed with powder high-concentrate diet(forage:concentrate=4:6,n=4)and treatment group fed with pellets high-concentrate diet(forage:concentrate=4:6,mixed with MgO:Sodium hydrophosphate:Sodium butyrate:Sodium acetate=2:3:5:5,n=4).20 weeks later,rumen fluid,blood samples from hepatic vein,portal vein and jugular vein as well as liver tissue were collected for further analysis.The data showed that,rumen pH was higher in treatment group and there was no time for pH<5.8 compared to control group.Also,the concentration of LPS in hepatic vein and portal vein was significantly lower in treatment group than control group(p<0.01).Besides,the mRNA relative expression of immune genes IKK,I?B,NF-?B,IL-1?,IL-10,LBP and the phosphorylation levels of protein p38,ERK were obviously lower in treatment group compared with control group(p<0.05).Meanwhile,the concentration of pro-inflammatory cytokines IL-6 and TNF-a in peripheral blood was significantly lower in treatment group than control group.Moreover,there was a positive correlation between LPS and protein p38,ERK activation in the liver.In conclusion,immune responses to high-concentrate diet could be reduced by dietary changes in dairy goats,and lower the risk of SARA.4.Impact of Saccharomyces cerevisiae fermentation product(SCFP)on rumen and feces LPS as well as acute phase responses during SARA in dairy cowsSaccharomyces cerevisiae fermentation product has been used in many studies to reduce the risk of SARA in dairy but varies results were conducted.12 Holstein cows fixed with rumen cannula fed with 45%concentrate diet were randomly assigned into two groups from-3 week relative to calving,control group fed with a diet added with 140 g/d corn and treatment group fed with a diet added with 126 g/d corn and 14 g/d SCFP.At the week 5 after calving,increased the concentrate to 70%to induce SARA in two groups and rumen,feces and peripheral blood samples were taken weekly for LPS and acute phase proteins analysis until 7 weeks after calving.The results showed that,during SARA week,the concentration of rumen and feces LPS increased significantly(p<0.05),as well as acute phase proteins SAA and Hp(p<0.05).However,SCFP tended to reduce the rumen LPS,and the decrease of the concentration of SAA,Hp was more obviously after SARA week compared to control group without significant.Furthermore,there was a positive correlation between rumen LPS and feces LPS,SAA as well as Hp in peripheral blood.So high-grain diet can induce SARA in dairy cows,but the effect of SCFP on SARA controlling was not obviously.5.Impact of increasing Saccharomyces cerevisiae fermentation product(SCFP) content in the diet on acute phase responses during SARA in dairy cowsPrevious studies reported that Saccharomyces cerevisiae fermentation product(SCFP)could influence the growth of rumen microbiota and stabilize the rumen pH,play an important role in the degradation of fiber in rumen and the nutrition absorption in digestive tract.18 Holstein cows fixed with rumen cannula fed with 45%concentrate diet were randomly assigned into three groups from-3 week relative to calving,control group(140 g/d corn),SCFP1 group(121 g/d corn +19 g/d SCFP)and SCFP2 group(102 g/d corn +38 g/d SCFP)(n=6).At the week 5 after calving,increased the concentrate to 70%to induce SARA in three groups and the rumen,feces and peripheral blood samples were taken weekly for LPS and acute phase proteins analysis until 7 weeks after calving.The data indicated that,during SARA week,rumen pH dropped dramatically(p<0.01),the rumen and feces LPS(p<0.01)as well as acute phase proteins SAA,Hp(p<0.05)in peripheral blood were increased.However,increase the SCFP content couldn't influence the rumen pH or feces LPS but tended to reduce rumen LPS(p=0.07).Besides,after SARA week,compare to control group,the concentration of SAA(p=0.05),Hp(p=0.06)and LBP(p=0.04)in peripheral blood in SCFP2 was lower,while the decrease of SAA(p=0.41),Hp(p=0.50)and LBP(p=0.06)in SCFP1 was not significant.Moreover,there was a positive correlation between rumen LPS and feces LPS,SAA as well as Hp in peripheral blood.This study further confirmed that the addition of Saccharomyces cerevisiae fermentation product could be able to improve the ability of resisting body damages in dairy cows with a weak dose-dependence. |
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