Rumen microbiome structure and metabolites activity in dairy cows with clinical and subclinical mastitis

Background:Due to the high prevalence and complex etiology,bovine mastitis(BM)is one of the most important diseases to compromise dairy cow health and milk quality.The shift in milk compositions has been widely investigated during mastitis,but recent studies suggested that gastrointestinal microorganism also has a crucial effect on the inflammation of other peripheral tissues and organs,including the mammary gland.However,research focused on the variation of rumen inner-environment during mastitis is still limited.Therefore,the ruminal microbial profiles,metabolites,and milk compositions in cows with different udder health conditions were compared in the present study.Furthermore,the correlations between udder health status and ruminal conditions were investigated.Based on the somatic cell counts(SCC),California mastitis test(CMT)parameters and clinical symptoms of mastitis,60 lactating Holstein dairy cows with similar body conditions(excepted for the udder health condition)were randomly divided into 3 groups(n=20 per group)including the healthy(H)group,the subclinical mastitis(SM)group and the clinical mastitis(CM)group.Lactation performance and rumen fermentation parameters were recorded.And rumen microbiota and metabolites were also analyzed via 16S rRNA amplicon sequencing and untargeted metabolomics,respectively.Results:As the degree of mastitis increased,rumen lactic acid(LA)(P<0.01),acetate,propionate,butyrate,valerate(P<0.001),and total volatile fatty acids(TVFAs)(P<0.01)concentrations were significantly decreased.In the rumen of CM cows,the significantly increased bacteria related to intestinal and oral inflammation,such as Lachnospiraceae(FDR-adjusted P=0.039),Moraxella(FDR-adjusted P=0.011)and Neisseriaceae(FDR-adjusted P=0.036),etc.,were accompanied by a significant increase in 12-oxo-20-dihydroxy-leukotriene B4(FDR-adjusted P=5.97×10^(−9))and 10beta-hydroxy-6beta-isobutyrylfuranoeremophilane(FDR-adjusted P=3.88×10^(−10)).Meanwhile,in the rumen of SM cows,the Ruminiclostridium_9(FDR-adjusted P=0.042)and Enterorhabdus(FDR-adjusted P=0.043)were increased along with increasing methenamine(FDR-adjusted P=6.95×10^(−6)),5-hydroxymethyl-2-furancarboxaldehyde(5-HMF)(FDR-adjusted P=2.02×10^(−6))and 6-methoxymellein(FDR-adjusted P=2.57×10^(−5)).The short-chain fatty acids(SCFAs)-producing bacteria and probiotics in rumen,including Prevoterotoella_1(FDRadjusted P=0.045)and Bifidobacterium(FDR-adjusted P=0.035),etc.,were significantly reduced,with decreasing 2-phenylbutyric acid(2-PBA)(FDR-adjusted P=4.37×10^(−6)).Conclusion:The results indicated that there was a significant shift in the ruminal microflora and metabolites associated with inflammation and immune responses during CM.Moreover,in the rumen of cows affected by SM,the relative abundance of several opportunistic pathogens and the level of metabolites which could produce antibacterial compounds or had a competitive inhibitory effect were all increased.

An overview of aflatoxin B1 biotransformation and aflatoxin M1 secretion in lactating dairy cows

Milk is considered a perfect natural food for humans and animals.However,aflatoxin B1(AFB1)contaminating the feeds fed to lactating dairy cows can introduce aflatoxin M1(AFM1),the main toxic metabolite of aflatoxins into the milk,consequently posing a risk to human health.As a result of AFM1 monitoring in raw milk worldwide,it is evident that high AFM1 concentrations exist in raw milk in many countries.Thus,the incidence of AFM1 in milk from dairy cows should not be underestimated.To further optimize the intervention strategies,it is necessary to better understand the metabolism of AFB1 and its biotransformation into AFM1 and the specific secretion pathways in lactating dairy cows.The meta-bolism of AFB1 and its biotransformation into AFM1 in lactating dairy cows are drawn in this review.Furthermore,recent data provide evidence that in the mammary tissue of lactating dairy cows,aflatoxins significantly increase the activity of a protein,ATP-binding cassette super-family G member 2(ABCG2),an efflux transporter known to facilitate the excretion of various xenobiotics and veterinary drugs into milk.Further research should focus on identifying and understanding the factors that affect the expression of ABCG2 in the mammary gland of cows.

Dietary supplementation with inulin improves lactation performance and serum lipids by regulating the rumen microbiome and metabolome in dairy cows

This study investigated the effects of inulin on rumen fermentation parameters,ruminal microbiome and metabolites,as well as lactation performance and serum indexes in dairy cows.Sixteen Holstein dairy cows with similar body conditions were randomly divided into 2 groups(n=8 per group),with inulin addition at 0 and 200 g/d percow.The experiment lasted for 6 weeks,including a 1-week adaptation period and a 5-week treatment period.At the end of the experimental period,the milk,serum and rumen fluid were sampled and analyzed.The microbiome and metabolome in the rumen fluid were analyzed via 16 S rRNA sequencing and untargeted metabolomics,respectively.The results showed that supplementation with inulin(200 g/d per cow)increased the milk yield(P=0.001),milk protein(P=0.032),lacto se rate(P=0.004)and proportion of saturated fatty acids(SFA)in milk(P<0.001),but decreased the proportion of unsaturated fatty acids(USFA)(P=0.041).Rumen pH(P=0.040)and the concentration of NH3-N(P=0.024)were decreased;however,acetate(P<0.001),propionate(P=0.003),butyrate(P<0.001)and lactic acid(LA)(P=0.043)were increased.The total cholesterol(TC)(P=0.008)and triglycerides(TG)(P=0.01)in serum were also reduced.Additionally,inulin addition elevated the relative abundance of several beneficial symbiotic and short-chain fatty acid(SCFA)-producing bacteria,such as Muribaculaceae(false discovery rate[FDR]-adjusted P<0.01),Acetitomaculum(FDR-adjusted P=0.043),and Bu tyrivibrio(FDR-adjusted P=0.036),while elevating the levels of L-lysine(FDR-adjusted P=4.24×10^(-3)),L-proline(FDR-adjusted P=0.0158),and L-phenylalanine(FDRadj usted P=0.027).In contrast,several pathogens and ruminal bacteria abu ndant in high-fat diets,such as Escherichia-Sh igella(FD R-adj usted P=0.022),Erysipelo trichaceaeUCG-004(FD R-adjusted P<0.01)and RF39(FDR-adjusted P=0.042)were decreased along with the reduction of lysophosphatidylcholine(LysoPC)(18:1(9 Z))(FDR-adjusted P=1.03×10^(-3)),LysoPC(16:0)(FDR-adjusted P=0.0108),LysoPC(18:2(9 Z,12 Z))(FDRadjusted P=1.65×10^(-3))and 8-methylnonenoate.In conclusion,dietary inulin supplementation could increase the relative abundance of commensal microbiota and SCFA-producing bacteria,upregulate amino acidmetabolism and downregulate lipid metabolism in the rumen of dairy cows,which might further improve lactation performance and the level of serum lipids.