Effect And Mechanism Of Dietary Starch Source And Organic Acid Pretreated Corn On Ruminal Acidosis In Dairy Goats

Subacute ruminal acidosis(SARA)is a common nutritional metabolic disease in ruminants under industrial feeding status.It is usually caused by the rapid decline of rumen pH from rapid fermentation of a large amount of starch in the rumen during high-grain diet,accompanied with release and translocation of digestive tract toxic substances including lipopolysaccharide(LPS),resulting in the inflammatory response.SARA is not only accompanished with some other nutritional metabolic dieseases,endangers animal health,but also leads to decrease of animal production performance.Varies studies have beed done to prevent SARA,this study firstly verified that reducing ruminal digestibility of cereal grains could be an effctively alleviate SARA with an animal trial,and figure out and effective way to treat grain to reduce the rumial digestibility in vitro.Finally,an in vivo was carried out to verify that the treatment can prevent SARA usefully.Five parts are included in this thesis.Trail 1,Effects of concentrate source and concentration on ruminal fermentation patterns and inflammatory responses in dairy goatsEight lactating dairy goats(35 ± 3.1 kg of body weight,140 ± 8.2 days of day in milk)with ruminal cannulas were used in a replicated 4×4 Latin square design with 2×2 factorial arrangement of treatments.Each experimental period consisted of 24 days long including 21 days for adaption and 3 days for data and sample collection.The four treatment diets were:corn and wheat grain combined with low(LS)and high grain starch(HS).Goats were fed equal amounts of a total mixed ration twice daily at 0700 and 1900 hours.Replacing corn with wheat in goat diet led to longer(P<0.02)duration of ruminal pH<5.6,higher ruminal LPS(P<0.05),but lower fecal LPS concentration.However,no differences between two grains in ruminal pH(mean,minimum and maximum),volatile fatty acids(VFA)and lactic acid concentration were observed.Goats fed HS diets had lower(P<0.01)ruminal pH and higher(P<0.01)ruminal concentrations of VFA and lactic acid,as well as higher(P<0.01)ruminal and fecal LPS concentrations.Starch source did not affect DMI,milk yields and milk components whereas feeding HS versus LS diet had higher milk yield,lactose yields and milk efficiency(P<0.05).Feeding wheat-versus corn-based diet showed only greater(P<0.05)concentration of toll-like receptor-4,whereas feeding the HS versus LS diet consistently increased blood concentrations of amyloid A,haptoglobin,LPS binding protein,and LPS(P<0.05).Analysis of Pearson correlation coefficients illustrated that the ruminal LPS concentration is more important than fecal LPS in inflammatory responses.In conclusion,HS diet led to greater SARA risk in dairy goats and reduce the ruminal digestibility of cereal grains could be a potential to prevent SARA.Trail 2,Effects of concentrate source and concentration on ruminal bacterial population in dairy goatsRuminal fluid and content were collected from the dairy goats of trail 1 on day 24.The mixture of the ruminal fluid and content were used for DNA extraction and then did the high-throughput sequencing.The effective Tag and trimmed Tag was not affected by starch source,however,the number of OTU was decreased(P<0.05)by wheat treatment.Both the effectiveTag and trimmed Tag was greater(P<0.05)in high starch diet,but the number of OTU was lower compare with low starch diet.No interaction was observed between starch source and concentration.The percentage of Cyanobacteria was greated in wheat group(P<0.05),and the percentage of Bacteroidetes and Actinobacteria and the ratio of Bacteroidetes to Firmicutestended to be greater(P<0.10),while the percentage of Candidate division TM7 andSynergistetes tended to be less.Compared with low starh diet,the percentage of Bacteroidetes,Proteobacteria,Tenericutes,Candidate division SRI and Unclassified bacteria and the ratio of Bacteroidetes to Firmicutes were less(P<0.05)in high starch diet,and the percentage of Synergistetes tended to be less(P<0.10).However,the percentages of Firmicutes and Euryarchaeota were greater(P<0.05)and Candidate division TM7 tended to be greater(P<0.10)in high starch diet.The analysis based on general level showed that compared with corn,wheat group increased(P<0.05)the percentage of Prevotella,Unclassified Gastranaerophilales and Quinella,tended to increase(P<0.10)the percentage of Butyrivibrio,Unclassified Veillonellaceae and Selenomonas,however,the percentage of Unclassified Ruminococcaceae,RC9 gut group,Unclassified Lachnospiraceae,Incertae Sedis and Unclassified Erysipelotrichaceae were decreased significantly(P<0.05).Compared to low starch diet,the high starch treatment increased(P<0.05)the percnetage of Unclassified Ruminococcaceae,Unclassified Christensenellaceae,Unclassified BS11 gut group,RC9 gut group,Butyrivibrio,Unclassified S24-8,Methanobrevibacter,Incertae Sedis,Saccharofermentans,Unclassified Erysipelotrichaceae and Quinella,but decreased(P<0.05)the percentage of Prevotella,Unclassified Prevotellaceae,Unclassified RF16,Succiniclasticum,Unclassified RF17 and Selenomonas.The correlation analysis based on the phylum level indicated that the concentration of ruminal LPS was posotively correlated with the percentage of Firmicutes(r =0.5;P<0.05),and the correlation analysis based on the general level demonstrated that the concentration of ruminal LPS was positively correlated with the percentage of Christensenellaceae and Quinella(r = 0.66 and 0.62,respectively;P<0.05).In conclusion,the SARA inducted by high grain diet may characteritice with the increase of Bacteroidetes and the decrease of Firmicutes.The increased ruminal LPS during SARA inducted by high grain diet may be caused of the rapid growth of Christensenellaceae and Quinella.Trail 3,The exploration of using pretreatment with different organic acids to alleviate SARAWater,lactic acid,citric acid and phophoric acid in the concentration of 0.5%,1%and 5%were used to steep the corn starch at room temperature or 55?.The pretreated starch was mixed with ground Chinese legume chunensis hay(1-mm)in the ratio of either 7:3 or 3:7 as the high starch substrate or the low starch substrate.In low starch diet,no changes were observed among different acid type,while the pH of the fermentation liquid was decreased(P<0.05)with the treatment of the acid concentration of 5%,however,the concentration of lactic acid and total VFA in the fermentation liquid was not affected by the acid concentrations.In high starch diet,the pH of fermentation liquid was greater(P<0.05),and the concentration of VFA and lactic acid tended(P<0.10)to be less in citric aicd group.Though the pH of the fermentation liquid in the treatment of acid concentration of 0.5%and 1%was not different with the control,but significantly greater(P<0.05)than the treatment of 5%.Temperature had no effects on either the pH of fermentation liquid or the concentration of VFA and lactic acid in the fermentation liquid.No differences of the starch granules were observed among either different acid types or the heat treatment in the SEM pictures,however,the acid concentration of 5%increase the holes on the surface of the starch granules,which indicated that the starch granules may start to acidolysis when the acid concentration increased to 5%.This study concluded that the pretreatment with citric acid in the concentration of 0.5%and 1%maight have some benefits on increasing the resistance of corn to against the ruminal fermentation.Trail 4,The exploration of the optimal process on corn pretreated with citric acid to alleviate SARA using batch cultureGround corn(2 mm)was steeped in an equal quantity(i.e.,in a ratio of 1:1,w/v)of tap water alone(Ctr),of 0.5%(Low)or 1%(High)CA solution for 12,24 or 48 hours.Gas production(GP),VFA,NH3-N and dry matter(DM)disappearance(DMD)were estimated at 6 and 24 h of incubation.Inoculums were obtained from three ruminally cannulated beef heifers fed a diet consisted of 30%barley silage,67%dry rolled barley and 3%vitamin and mineral supplement(DM basis).No interaction between CA solution and steeping time were detected on CA treated corn chemical composition,GP kinetics,DMD and fermentation parameters and production of CH4,H2 and CO2.Resistant starch(RS)content was greater(P<0.05)with CA versus Ctr,whereas no differences in RS contents were observed between Low and High CA treatments.Soluble starch was highest(P<0.05)with 12 h,intermediate with 24 h and lowest with 48 h steeping time,while RS was greater(P<0.05)at 48 h steeping time with no difference between 12 and 24 h steeping time.Either Low or High CA treatments versus Ctr had lower(P<0.05)asymptotic cumulative GP,GP rate,concentrations of VFA and NH3-N,and DMD at 24 h of incubation.None of these variables differed between Low and High CA treatment except that GP rate was lower(P<0.05)with High CA treatment.Rate of GP,DMDand NH3-N concentration were highest(P<0.01)with 12 h,intermediate with 24 h and lowestwith 48 h steeping time at 24 h of incubation,but VFA concentration did not differ between 24 and 48 h of steeping time.Ratio of acetate to propionate was greater(P<0.05)with Low CA than Ctr as well as it was greater(P<0.01)with 24 and 48 h than 12 h of steeping time.Production of CH4 and CO2 decreased(P<0.05)either by CA treatment or increasing steeping time.These results indicated that CA treated ground corn increased RS content,altered fermentation pattern for more acetate production and decreased ruminal DMD in batch culture.Use of CA to treat corn grain can be an effective processing to reduce ruminal digestion of starch,and thus potentially alleviate risk of rumen acidosis.Trail 5,Effects of feeding citric acid pretreated corn on ruminal fermentationpatterns and inflammatory responses in dairy goats Eight ruminally cannulated Saanen dairy goats were used in a crossover design experiment.Each experimental period was lasted 21 day long including 14 days for adaption to new diet and 7 days for sampling and data collection.The goats were fed high grain diet contained 30%hay and 70%corn-based concentrate.The corn was steeped either in water(control)or in 0.5%(wt/vol)citric acid(CA)solution for 48 h.Goats fed CA diet showed improved ruminal pH status with greater mean and minimum ruminal pH,and shorter(P<0.05)duration of ruminal pH<5.6 and less area of ruminal pH<5.6,5.8 and 6.0.Concentration of total volatile fatty acid and molar proportion of propionate were less but the molar proportion of acetate was greater(P<0.05)in goats fed the CA diet than the control diet.Concentration of ruminal LPS was lower(P<0.05)and that of lactic acid also tended(P<0.10)to be lower in goats fed CA than the control.Although dry matter intake,actual milk yield,yield and content of milk protein and lactose were not affected,the milk fat content and 4%fat-corrected milk tended(P<0.10)to be greater in goats fed CA diet.For the inflammatory responses,peripheral LPS did not differ,whereas the concentration of LPS binding protein and serum amyloid A tended(P<0.10)to be less in goats fed CA diet.Similarly,goats fed CA diet had less(P<0.05)concentration of haptoglobin and tumor necrosis factor.These results indicated that feeding ground corn treated with CA effectively improved ruminal pH status,thus alleviated the risk of ruminal acidosis,reduced inflammatory response,and tend to improve milk yield and milk fat test.