Study On The Mechanism Of Laminitis Induced By Ruminal Acidosis In Goat

Laminitis is a diffuse,non-infectious inflammation of the lamella(including epidermal lamella and dermal lamella).The symptom of laminitis includes digital soften,yellowish coloration and white line separations.Laminitis makes animal lie down in the long term,decrease of feed intake and difficult evaluation of estrus,which induces large economic loss.Feeding high-grain diet has been a normal phenomenon in cattle and goat farming because of limited forage and producer chasing economic interest overly in china.Previous researches showed that long-term feeding high-grain may result in lameness,however,the mechanism underlying the relationship between high grain feeding and occurrence of lameness is not very clear.In present study,we investigated the mechanism of lameness induced by rumen acidosis in goats,and the thesis consisted of three sections as following:1.Effect of acute ruminal acidosis induced by fructooligosaccharide on ruminal fermentation,structure of hooves and mRNA expression of inflammatory cytokines and matrix metalloproteinase genes in goat hoovesThe present study was conducted to investigate the effect of intragastric administration of fructooligosaccharide on ruminal fermentation,mRNA expression of pro-inflammatory cytokines and matrix metalloproteinase genes in crossbred boer-goat hooves.Eight healthy goats was randomly divided into two groups,including the control(n=4)and the treatment group which was treated with fructooligosaccharide infusion(n=4,21 g/kg BW).Ruminal liquid and blood were collected respectively at 0 h(before infusion),4 h,8 h,12 h,24 h,48 h and 0 h,4 h,8 h,24 h and 48 h after infusion.The goats were slaughtered after 48 h of infusion.The result showed that,as compared with the control,fructooligosaccharide infusion decreased the ruminal pH(P<0.001)and total volatile fatty acid(P<0.001),while increased the concentration of lactic acid(P<0.001)and LPS(P<0.001)in rumen and blood.Results of histology suggest that the fructooligosaccharide infusion shortened secondary epidermal lamellae and secondary dermal lamellae compared with the control.The Realtime-PCR results revealed that the fructo-oligosaccharide infusion reduced the mRNA expression of TIMP-1(P<0.05)genes and increased the relative mRNA expression of IL-6(P<0.05)genes,MMP-2(P<0.05)genes and MT1-MMP(P<0.05)genes in goat hooves.In conclusion,intragastric administration of fructo-oligosaccharide induces the disorder of ruminal fermentation and increased concentrations of LPS and lactic acid in rumen and blood,which further causes the changes of mRNA expression of pro-inflammatory cytokines and matrix metalloproteinase genes in goat hooves,and finally induced the laminitis in goats.2.Effects of subacute ruminal acidosis on rumen fermentation and mRNA expression of pro-inflammatory cytokines and matrix metalloproteinase genes in goat hoovesThe present study aimed to investigate the effect of subacute ruminal acidosis induced by long-term high-grain diet on ruminal fermentation,mRNA expression of pro-inflammatory cytokines and matrix metalloproteinase genes in crossbred boer-goat hooves.In the present study,12 male goats were randomly assigned to either a group fed a hay diet(0%grain;n = 6)or a group fed an HG diet(75%grain;n = 6)to characterize the changes in the mRNA expression of pro-inflammatory cytokines and MMP,MT1-MMP,and TIMP-1 in the lamellar tissue.After 7 weeks,the HG diet had decreased the ruminal pH(P<0.001),had increased the concentrations of total volatile fatty acids(P<0.001)and lactate(P<0.001)in the rumen,and had increased the lipopolysaccharide level(P<0.05)in the blood.HG diet feeding increased the mRNA expression of IL-1β,IL-6,TNF-α,and MMP-2 in the lamellar tissues of HG goats compared with the hay group(P<0.05),while no significant differences were observed in the mRNA expression of TIMP-1 and MMP-9 between the two groups(P>0.05).Correlation analysis revealed that the pro-inflammatory cytokine mRNA expression was positively correlated with MMP-2 expression in lamellar tissues.Collectively,these results reveal that HG diet feeding could activate the inflammatory response in lamellar tissues,which may further contribute to the process of laminar damage.3.Effect of subacute ruminal acidosis on expression of proteins in goat hooves based on proteomicsThis study was conducted to investigate the effect of subacute ruminal acidosis induced by long-term high-grain diet on expression of protein in hooves.Twelve healthy goats was randomly divided into two groups,including the control(n=6)and the treatment group which was fed with high-grain diet(n=6).Goats were slaughtered after feeding of seven weeks.Samples were analyzed by comparative proteomics.Results showed that 20 kinds of differentially expressed proteins were identified in the lamellar tissue of goat fed high-grain diet between the high grain group and hay group,of them,9 proteins were differentially up-regulated and 11 down-regulated.These differential proteins were mainly involved in carbohydrate metabolism,lipids metabolism,molecular transport,immune regulation,inflammatory response,oxidative stress.Generally,there was a significant change in the abundance of protein expression level between the goats fed high grain diet and goats fed hay diet,and some differentilally protein observed was associated with the occurance of lameness.