Milk metabolome reveals variations on enteric methane emissions from dairy cows fed a specific inhibitor of the methanogenesis pathway

摘要

Metabolome profiling in biological fluids is an interestingapproach for exploring markers of methane emissionsin ruminants. In this study, a multiplatform metabolomicsapproach was used for investigating changesin milk metabolic profiles related to methanogenesis indairy cows. For this purpose, 25 primiparous Holsteincows at similar lactation stage were fed the same dietsupplemented with (treated, n = 12) or without (control,n = 13) a specific antimethanogenic additive thatreduced enteric methane production by 23% with nochanges in intake, milk production, and health status.The study lasted 6 wk, with sampling and measuresperformed in wk 5 and 6. Milk samples were analyzedusing 4 complementary analytical methods, including2 untargeted (nuclear magnetic resonance and liquidchromatography coupled to a quadrupole-time-of-flightmass spectrometer) and 2 targeted (liquid chromatography-tandem mass spectrometry and gas chromatographycoupled to a flame ionization detector) approaches.After filtration, variable selection and normalizationdata from each analytical platform were then analyzedusing multivariate orthogonal partial least square discriminantanalysis. All 4 analytical methods were ableto differentiate cows from treated and control groups.Overall, 38 discriminant metabolites were identified,which affected 10 metabolic pathways includingmethane metabolism. Some of these metabolites suchas dimethylsulfoxide, dimethylsulfone, and citramalicacid, detected by nuclear magnetic resonance or liquidchromatography-mass spectrometry methods, originatedfrom the rumen microbiota or had a microbialhostanimal co-metabolism that could be associatedwith methanogenesis. Also, discriminant milk fattyacids detected by targeted gas chromatography weremostly of ruminal microbial origin. Other metabolitesand metabolic pathways significantly affected were associatedwith AA metabolism. These findings providenew insight on the potential role of milk metabolitesas indicators of enteric methane modifications in dairycows.