Changes of the liver metabolome following an intravenous lipopolysaccharide injection in Holstein cows supplemented with dietary carnitine

Background:Carnitine facilitates the flux of long-chain fatty acids for hepatic mitochondrial beta-oxidation,which acts to ameliorate the negative energy balance commonly affecting high-yielding dairy cows.Inflammation triggered by lipopolysaccharide(LPS)load can however pose a challenge to the metabolic integrity via the expression of pro-inflammatory mediators,leading to immune system activation and respective metabolic alterations.The effect of enhanced carnitine availability on hepatic metabolome profiles during an inflammatory challenge has not yet been determined in dairy cows.Herein,Holstein cows were supplemented with 25 g/d rumen-protected carnitine from 42d prepartum until 126 d postpartum(n=16)or assigned to the control group with no supplementation during the same period(n=14).We biopsied the liver of the cows before(100 d postpartum)and after(112 d postpartum)an intravenous injection of 0.5μg/kg LPS.Liver samples were subjected to a targeted metabolomics analysis using the AbsoluteIDQ p180 Kit(Biocrates Life Sciences AG,Innsbruck,Austria).Results:Multivariate statistical analyses revealed that hepatic metabolome profiles changed in relation to both the carnitine supplementation and the LPS challenge.Comparing the metabolite profiles on 100 d,carnitine increased the concentration of short-and long-chain acyl-carnitines,which may be explained by an enhanced mitochondrial fatty acid shuttle and hence greater energy availability.The LPS injection affected hepatic metabolite profiles only in the carnitine supplemented group,particularly altering the concentration of biogenic amines.Conclusions:Our results point to interactions between an acute hepatic inflammatory response and biogenic amine metabolism,depending on energy availability.

Yak rumen microbiome elevates fiber degradation ability and alters rumen fermentation pattern to increase feed efficiency

Rumen microbes play an important role in ruminant energy supply and animal performance.Previous studies showed that yak(Bos grunniens)rumen microbiome and fermentation differ from other ruminants.However,little is understood about the features of the rumen microbiome that make yak adapted to their unique environmental and dietary conditions.This study was to investigate the rumen microbiome and metabolome to understand how yak adapt to the coarse forage and harsh environment in the Qinghai-Tibetan plateau.Nine female Qaidam yellow cattle(Bos taurus),9 dzomo(hybrids of cattle and yak)and 9 female plateau yak(B.grunniens),about 5 to 6 years old,were used in this study.Rumen fermentation parameters,fibrolytic enzyme activities,and rumen metataxonomic were determined.Then 18(6 samples per group)were selected for rumen metagenomic and metabolome analysis.Metataxonomic analysis revealed that the rumen microbiota was significantly different among plateau yak,Qaidam yellow cattle,and dzomo(P<0.05).Metagenomic analysis displayed a larger gene pool encoding a richer repertoire of carbohydrate-active enzymes in the rumen microbiome of plateau yak and dzomo than Qaidam yellow cattle(P<0.05).Some of the genes encoding glycoside hydrolases that mediate the digestion of cellulose and hemicellulose were significantly enriched in the rumen of plateau yak than Qaidam yellow cattle,but glycoside hydrolase 57 that primarily includes amylases was abundant in Qaidam yellow cattle(P<0.05).The rumen fermentation profile differed also,Qaidam yellow cattle having a higher molar proportion of acetate but a lower molar proportion of propionate than dzomo and plateau yak(P<0.05).Based on metabolomic analysis,rumen microbial metabolic pathways and metabolites were different.Differential metabolites are mainly amino acids,carboxylic acids,sugars,and bile acids.Changes in rumen microbial composition could explain the above results.The present study showed that the rumen microbiome of plateau yak helps its host to adapt to the Qinghai-Tibetan plateau.In particular,the plateau yak rumen microbiome has more enzymes genes involved in cellulase and hemicellulase than that of cattle,resulting higher fibrolytic enzyme activities inyak,further providing stronger fiber degradation function.