Susceptibility of dairy cows to subacute ruminal acidosis is reflected in both prepartum and postpartum bacteria as well as odd-and branched-chain fatty acids in feces

Background:The transition period is a challenging period for high-producing dairy cattle.Cows in early lactation are considered as a group at risk of subacute ruminal acidosis(SARA).Variability in SARA susceptibility in early lactation is hypothesized to be reflected in fecal characteristics such as fecal pH,dry matter content,volatile and odd-and branched-chain fatty acids(VFA and OBCFA,respectively),as well as fecal microbiota.This was investigated with 38 periparturient dairy cows,which were classified into four groups differing in median and mean time of reticular pH below 6 as well as area under the curve of pH below 6.Furthermore,we investigated whether fecal differences were already obvious during a period prior to the SARA risk(prepartum).Results:Variation in reticular pH during a 3-week postpartum period was not associated with differences in fecal pH and VFA concentration.In the postpartum period,the copy number of fecal bacteria and methanogens of unsusceptible(UN)cows was higher than moderately susceptible(MS)or susceptible(SU)cows,while the genera Ruminococcus and Prevotellacea_UCG-001 were proportionally less abundant in UN compared with SU cows.Nevertheless,only a minor reduction was observed in iso-BCFA proportions in fecal fatty acids of SU cows,particularly iso-C15:0and iso-C16:0,compared with UN cows.Consistent with the bacterial changes postpartum,the lower abundance of Ruminococcus was already observed in the prepartum fecal bacterial communities of UN cows,whereas Lachnospiraceae_UCG-001 was increased.Nevertheless,no differences were observed in the prepartum fecal VFA or OBCFA profiles among the groups.Prepartum fecal bacterial communities of cows were clustered into two distinct clusters with 70%of the SU cows belonging to cluster 1,in which they represented 60%of the animals.Conclusions:Inter-animal variation in postpartum SARA susceptibility was reflected in post-and prepartum fecal bacterial communities.Differences in prepartum fecal bacterial communities could alert for susceptibility to develop SARA postpartum.Our results generated knowledge on the association between fecal bacteria and SARA development which could be further explored in a prevention strategy.

Coordinated response of milk bacterial and metabolic profiles to subacute ruminal acidosis in lactating dairy cows

Background Bovine milk is an important source of nutrition for human consumption,and its quality is closely associated with the microbiota and metabolites in it.But there is limited knowledge about the milk microbiome and metabolome in cows with subacute ruminal acidosis.Methods Eight ruminally cannulated Holstein cows in mid lactation were selected for a 3-week experiment.The cows were randomly allocated into 2 groups,fed either a conventional diet(CON;40%concentrate;dry matter basis)or a high-concentrate diet(HC;60%concentrate;dry matter basis).Results The results showed that there was a decreased milk fat percentage in the HC group compared to the CON group.The amplicon sequencing results indicated that the alpha diversity indices were not affected by the HC feeding.At the phylum level,the milk bacteria were dominated by Proteobacteria,Actinobacteria,Bacteroidetes,and Firmicutes both in the CON and HC groups.At the genus level,the HC cows displayed an improved proportion of Labrys(P=0.015)compared with the CON cows.Results of both the principal components analysis and partial least squares of discriminant analysis of milk metabolome revealed that samples of the CON and HC groups clustered separately.A total of 31 differential metabolites were identified between the two groups.Of these,the levels of 11 metabolites decreased(α-linolenic acid,prostaglandin E2,L-lactic acid,L-malic acid,3-hydroxysebacic acid,succinyladenosine,guanosine,pyridoxal,L-glutamic acid,hippuric acid,and trigonelline),whereas the levels of the other 20 metabolites increased in the HC group with respect to the CON group(P<0.05).Conclusion These results suggested that subacute ruminal acidosis less impacted the diversity and composition of milk microbiota,but altered the milk metabolic profiles,which led to the decline of the milk quality.

Changes in feed intake, nutrient digestion, plasma metabolites, and oxidative stress parameters in dairy cows with subacute ruminal acidosis and its regulation with pelleted beet pulp

The objectives of this study were to 1） determine the variation of nutrient digestion, plasma metabolites and oxidative stress parameters triggered by induced subacute ruminal acidosis （SARA）; and 2） evaluate the ability of pelleted beet pulp （BP） as a replacement for ground corn to alleviate SARA. Eight Holstein-Friesian cows were fed four diets during four successive17 day periods： 1） total mixed ration （TMR） containing 0% finely ground wheat （FGW） （WO）; 2） TMR containing 10% FGW （W10）; 3） TMR containing 20% FGW （W20）; and 4） TMR containing 10% BP as a replacement for 10% ground corn （BP10）. The SARA induction protocol reduced the mean ruminal pH from 6.37 to 5.94, and the minimum ruminal pH decreased from 5.99 to 5.41 from baseline to challenge period. Mean ruminal pH increased from 5.94 to 6.05, and minimum daily ruminal pH increased from 5.41 to 5.63, when BP was substituted for corn. The apparent digestibility of nutrients was not affected by the dietary treatments, except that the digestibility of neutral detergent fibre （NDF） and acid detergent fibre （ADF） was reduced in cows fed the W20 diet compared with cows fed the W0 and W10 diets, and cows fed the BP10 diet had higher NDF and ADF digestibility than the cows fed the W20 diet. Cows fed the W20 diet had a lower plasma concentration of 13-hydroxybutyrate （BHBA）, non-esterified fatty acids （NEFA）, cholesterol, triglyceride, and total antioxidative capacity （TAC）, and a higher plasma concentration of glucose, insulin, malonaldehyde （MDA）, super oxygen dehydrogenises （SOD）, and glutathione peroxidase （GSH-Px） than cows fed the W0 diet. Substitution of BP for corn increased concentrations of plasma BHBA and TAC, but decreased concentrations of plasma MDA. Our results indicate that reduction of fibre digestion; the concomitant increase of plasma glucose and insulin; the decrease of plasma BHBA, NEFA, cholesterol, and triglyceride; and changes of plasma oxidative stress parameters are highly related to SARA induced by W20 diets. These variables may be alternative candidates for SARA diagnosis. We also suggest that the substitution of BP for corn could reduce the risk of SARA, increase fibre digestion, and improve the antioxidant status in dairy cows.

Long-term effect of subacute ruminal acidosis on the morphology and function of rumen epithelial barrier in lactating goats

Grain-induced subacute ruminal acidosis(SARA)impairs rumen epithelial barrier function,but it is yet to be determined if SARA can cause persistent damage to the morphology and function of the rumen epithelial barrier.The objective of the present study was to investigate if SARA has persistent effects on the morphological structure and permeability of ruminal epithelium and the expression of the genes involved in epithelial barrier function using a lactating goat model.Twelve mid-lactating Saanen goats with rumen cannulas were randomly assigned to 1 of 2 groups:control group(Ctrl,n=4)fed a basal diet with a non-fiber carbohydrate(NFC)to neutral detergent fiber(NDF)ratio of 1.40,and SARA group(SARA,n=8)fed the same basal diet but with increasing NFC to NDF ratio from 1.4 to 1.79,2.31,and 3.23 overtime to induce SARA.At the end of the SARA challenge(post-SARA),4 goats were randomly selected from the SARA group and fed only hay mixture ad libitum for another 4 weeks to allow for restitution(post-SARA).Ruminal pH was continuously recorded to monitor the severity of SARA.Samples of the ventral ruminal epithelium were collected after slaughter to examine the structural and functional changes of the ruminal epithelium using transmission electron microscopy(TEM),Ussing chambers,qRT-PCR,and Western bolt analyses.Compared with the Ctrl group,ruminal papilla length,width,surface area and thickness of stratum corneum increased(P<0.05),while stratum spinosum and basale thickness,and total depth of the epithelium decreased(P<0.05)in the SARA group.These changes diminished or tended to return to the levels of the Ctrl group in the post-SARA group(P>0.05).The SARA challenge also decreased cellular junction and widened the intercellular space between epithelial cells.Rumen transepithelial short-circuit current(Isc),tissue conductance(Gt),and mucosa-to-serosa flux of paracellular horseradish peroxidase(HRP)all increased(P<0.05)both in the SARA and post-SARA groups,which indicates that SARA can induce a sustained increase in epithelial permeability and barrier dysfunction.Moreover,the mRNA and protein expressions of CLDN1,OCLN and ZO-1 were down-regulated(P<0.01)in both the SARA and post-SARA groups.The results of this study showed that SARA could result in sustained epithelial barrier dysfunction,at both structural and functional levels,which is associated with decreased expression of rumen epithelial tight junction proteins,and the restitution of rumen epithelial barrier function is slower than that of its morphology.

Subacute ruminal acidosis in dairy herds:Microbiological and nutritional causes,consequences,and prevention strategies

Dairy cattle are frequently fed high-concentrate(HC)diets in modern intensive feeding systems,especially in the transition period.During this period,cows face many alterations that include hormonal changes and shifting to a lactating state.Switching to a HC diet that may disrupt the ruminal microbiota balance can lead to subacute ruminal acidosis(SARA).Moreover,the main factor shaping the rumen microbiota is dietary composition,especially the ratio of starch to fibrous carbohydrates.Feeding highly fermentable carbohydrate diets after adaptation to forage diets leads to a rumen fermentation rate that exceeds rumen absorption and buffering rates,resulting in a reduction in ruminal pH.As a result of Gram-negative bacterial cell lysis,an increase in harmful ruminal bacterial metabolites,including lipopolysaccharide,lactic acid,and histamine,is observed.The interactions between the host immune system and the ruminal microbiota play an essential role in many physiological processes and the development of the disorder.Progress in DNA sequencing and bioinformatics platforms provides new opportunities to investigate the composition of ruminal microbes and yields unique advances in understanding ecology of the rumen.Subacute ruminal acidosis is linked with a change in the ruminal microbiota structure and richness and with other metabolic disorders;such as rumenitis,milk fat depression,laminitis,and liver abscesses.Therefore,this review aims to explore a better understanding of the crosstalk between diet and microbiota in the prevalence of rumen acidosis and its consequences,which is crucial for control strategies such as feeding management,and supplementation with thiamine,prebiotics,and probiotics.

Responsive changes of rumen microbiome and metabolome in dairy cows with different susceptibility to subacute ruminal acidosis

Subacute ruminal acidosis(SARA)represents one of the most important digestive disorders in intensive dairy farms,and dairy cows are individually different in the severity of SARA risk.The objectives of the current study were to investigate differences in the ruminal bacterial community and metabolome in dairy cattle with different susceptibility to SARA.In the present study,12 cows were initially enrolled in the experiment.Based on average ruminal pH,4 cows with the lowest ruminal pH were assigned to the susceptible group(SUS,pH=5.76,n=4)and 4 cows with the highest ruminal pH assigned to the tolerant group(TOL,pH=6.10,n=4).Rumen contents from susceptible(SUS,n=4)and tolerant(TOL,n=4)dairy cows were collected through rumen fistula to systematically reveal the rumen microbial and metabolic alterations of dairy cows with different susceptibility to SARA using multi-omics approaches(16S and 18S rRNA gene sequencing and metabolome).The results showed that despite being fed the same diet,SUS cows had lower ruminal pH and higher concentrations of total volatile fatty acids(VFA)and propionate than TOL cows(P<0.05).No significant differences were observed in dry matter intake,milk yield,and other milk compositions between the SUS and TOL groups(P>0.05).The principal coordinates analysis based on the analysis of molecular variance indicated a significant difference in bacterial composition between the two groups(P=0.01).More specifically,the relative abundance of starch-degrading bacteria(Prevotella spp.)was greater(P<0.05),while the proportion of fiber-degrading bacteria(unclassified Ruminococcaceae spp.,Ruminococcus spp.,Papillibacter,and unclassified Family_-XIII)was lower in the rumen of SUS cows compared with TOL cows(P<0.05).Community analysis of protozoa showed that there were no significant differences in the diversity,richness,and community structure(P>0.05).Metabolomics analysis revealed that the concentrations of organic acids(such as lactic acid),biogenic amines(such as histamine),and bacterial degradation products(such as hypoxanthine)were significantly higher in the SUS group compared to the TOL group(P<0.05).These findings revealed that the higher proportion of starch-degrading bacteria/lower fiber-degrading bacteria in the rumen of SUS cows resulted in higher VFA-producing capacity,in particular propionate.This caused a disruption in metabolic homeostasis in the rumen which might be the reason for the higher susceptibility to SARA.Overall,these findings enhanced our understanding of the ruminal microbiome and metabolic changes in cows susceptible to SARA.

High-concentrate feeding upregulates the expression of inflammation-related genes in the ruminal epithelium of dairy cattle

Background： The objective of this study was to characterize the mRNA expression profile related to rumen epithelial inflammation through the in vivo and in vitro experiments. In the in vivo experiment, rumen papillae were collected from four dairy cows adapted to either a 40 % （LC） or 70 % （HC） concentrate feeds for microarray analysis. Results： Results showed that 245 differentially expressed genes （DEGs） were detected in the cows fed the HC relative to the LC diet. The DEGs were first annotated, and results revealed that the expression of inflammation- related genes, including IL-1t8, 1L-2, IL-22, CCL19, CCLS, CX3CR1, CXCL6, INHBE, LEPR, PRL, and TNFRSF9 found in the cytokine-cytokine receptor pathway were up-regulated in the HC-fed cows, indicating local inflammation in the rumen epithelium was triggered. The expression of IL-1~, 1l_-2, and IL-6 was further validated by qRT-PCR. To demonstrate whether there were relationships between cytokine mRNA expression and ruminal factors （pH and LPS）, the isolated ruminal epithelial cells were cultured in vitro. Results showed that the mRNA expression of IL-1, IL-2, IL-6, and IL-8 increased after the LPS treatment, while Iow-pH treatment elevated the mRNA expression of TNF-a, suggesting that Iow-pH coupled with higher levels of LPS in rumen of cows fed the HC may be mainly responsible for the triggered local ruminal inflammation. Conclusions： Our results indicate that ruminal local inflammation response might be triggered during HC feeding and these findings also enhance the knowledge of rumen epithelial adaptation to HC at the molecular level.

Effects of Increasing Non-Fiber Carbohydrate to Neutral Detergent Fiber Ratio on Rumen Fermentation and Microbiota in Goats

Six rumen-cannulated lactating Guanzhong goats were used to investigate changes in ruminal fermentation pattern and the microbiota following a subacute rtmainal acidosis （SARA） inducing procedure. Induction of SARA was performed by increasing dietary non-fiber carbohydrate （NFC） to neutral detergent fiber （NDF） ratio from 1.02 （stage 1） to 1.24 （stage 2）, 1.63 （stage 3） and 2.58 （stage 4）. A dynamic pH monitoring system, real-time fluorescent quantitative PCR and conventional anaerobic culture were used to assess changes in ruminal pH and microbiota. Results indicated that rumen fermentation patterns changed significantly with increased NFC：NDF ratio. The decline in ruminal pH was caused by increased ruminal total volatile fatty acids （TVFA）, which was mainly attributed to a significant increase in ruminal butyrate, rather than the accumulation of ruminal lactic acid. In addition, in the course of SARA, the number of rumen microoganisms altered significantly, with increases in ruminal amylolytic bacteria, Lactobacilli, Streptococcus bovis and Megasphaera elsdenii, the latter particularly dramatically indicating that it may be the main factor responsible for the increase in butyrate, and decrease in protozoa.