Effects Of Selenium Yeast On Plasma Metabolites Of Dairy Cows In Parturition Stress Using Untargeted Metabolomics

The comprehensive reactions such as metabolic stress and inflammation occured in dairy cows before and after calving are called “parturition stress”.Selenium has anti-inflammatory,anti-oxidant and immune-enhancing effects.It is an important supplement in dairy cows’ diets to reduce the incidence of mastitis,metritis or retained fetal membranes.However,the mechanism of selenium’s influence on plasma metabolites in perinatal cows is unclear.In order to reveal the effects of stress on dairy metabolic and the effect of selenium yeast supplementation on cow metabolism during parturition stress,we selected 24 healthy multiparous dairy cows with similar body condition scores,parity,age,and due date.They were randomly divided into a control group(group C)and a test group(group T),fed with basal diet supplemented with or without 0.15 g selenium yeast per kg dry matter(DM)from 21 days prepartum to calving.Two groups of venous blood were collected before morning-feeding 21 days before due date and within 6 hours after calving.Then collected the plasma by centrifugation.According to sampling time and feeding conditions,the samples were divided into C-21 d and T-21d(21d before due date),C-0d and T-0d(after the calving).The UHPLC-TOF/MS analysis technique was used to detect the metabolic profiles of the plasma in the positive and negative ion modes of each group on prepartum day 21 and calving.Then multivariate and univariate statistical methods were used to analyze the differences in plasma metabolites between different times and groups.And the bioinformatics analysis was performed to reveal biological pathways involved in differential metabolites.All of the results about this experiment are as follows:1.Change of plasma metabolites in dairy cows during parturition stress.The results showed that there were 65 different metabolites in plasma between C-0d group and C-21 d group.Compared with C-21 d group,the concentration of tryptophan,valine,leucine,glutamate,proline,tyrosine,histidine,arginine,carnosine,betaine,other amino acids and their derivatives significantly decreased(P<0.05);lipids significantly increased such as linoleic acid,arachidonic acid,phosphatidylcholine,palmitic acid and oleic acid(P<0.05);taurodeoxycholate,glycocholic acid,and taurochenodeoxycholate showed decreaseing trends.Whereas the chenodeoxycholate and deoxycholic acid showed increasing trends(0.05<P<0.1);lactic acid,glucose,mannose,and lactose significantly increased(P<0.05).These metabolic changes suggested that the decline in dry matter intake in dairy cows leads to a negative energy balance of the body,resulting in amino acid metabolism enhancement and gluconeogenesis reduction.On the other hand,stress stimulation and inflammatory response during the delivery exacerbate lipid metabolism.2.Effect of selenium yeast on the metabolism of dairy cows during parturition stress.The results showed that there were 47 differential metabolites in the plasma between the T-0d group and the C-0d group.After selenium supplement,plasma amino acids such as phenylalanine,leucine,glutamic acid,proline and isoleucine significantly decreased,and amino acid derivatives such as betaine and carnosine significantly increased(P<0.05);the concentration of lipids such as linoleic acid,arachidonic acid,palmitic acid,oleic acid and other fatty acids showed decreasing trends(0.05<P<0.1);glucose,mannose,and lactose were increasing tendency,lactic acid showed a decreasing trend(0.05<P<0.1),citric acid significantly increased(P<0.05);indoxyl sulfate significantly increased(P<0.05)and niacinamide increased tendency(0.05<P<0.1).These metabolic changes suggested that selenium can relieve the stress and inflammatory response of transition cows during parturition stress by promoting the synthesis of antioxidant amino acid derivatives,tricarboxylic acid cycle,indoxyl sulfate and niacinamide metabolism.Meanwhile,the lipids metabolism reduced.Conclusion:(1)Parturition stress down-regulated amino acid metabolism and up-regulated lipids and glucose metabolism in dairy cows.(2)Selenium supplement in early perinatal period relived parturition stress by promoting the metabolism of anti-inflammatory or anti-oxidative amino acid derivatives and reducing the metabolism of pro-inflammatory lipids.