Effect Of Supplementation With Selenium Yeast In Prepartum Dietary On Plasma Proteomics Of Dairy Cows In Parturition

The transition period is an important period for the production and reproduction of dairy cows.It usually refers to the period from 3 weeks before calving to 3 weeks after calving.The occurrence of negative energy balance,calving and lactation causes the cows susceptible of nutrient metabolic diseases or reproductive disease at this stage.Selenium,as an essential trace element for animals,exerts antioxidant and anti-inflammatory functions in the form of selenoproteins and plays an important role in the health of dairy cows.This study screened 24 cows with similar body conditions and randomly divided them into two groups(C and T groups).Group C was fed with basal diet while group T added with selenium 0.3mg in per kilogram dry matter(DM)21 days before the expected date of production.The tail vein plasma was collected within 0-6 hours of colostrum harvesting.Proteins were extracted and digested,and the peptides were then subjected to iTRAQ labeling followed by LC-MS/MS proteomics test to screen for differences between the two groups.To verify the reliability of proteomics data,three protein-rich histamine glycoproteins(HRG),lipopolysaccharide binding protein(LBP),and serum amyloid 3(SAA3)were tested by ELISA.The results of this experiment are as follows:Study I: In this study,542 proteins was identified in the cow's plasma.The isoelectric point of these proteins was 5-12 and the relative molecular mass was 10-60 kD.The differentially expressed proteins were screened when T/C was greater than 1.2 or less than 0.83(P < 0.05).The results showed that there were 48 differential abundance proteins,of which 14 proteins were up-regulated and 34 proteins were down-regulated,among which ATP5A1 and SPP24 were significantly upregulated(P < 0.01).13 proteins such as GC,SCGB2A2,SERPINA3-2,DERA,SAA3,LBP,GPX3,CD177,CAT,LF,SCGB1 D,SERPINA3-3 and S100A8 were significantly down-regulated(P < 0.01).After GO annotation of all differential proteins,1501 GO entries were obtained at different levels,and 38 were enriched after Fisher's exact test.These include 27 biological process items such as response to bacterium,acute-phase response,positive regulation of lipid metabolic process,etc.9 molecular functional items such as coenzyme binding and transporter activity.2 cell component items are a spindle and a basal part of cell.LBP,ITIH4,SAA3,LOC510860 and AGT participating in the acute phase reaction process,were significantly down-regulated.APOA1,APOC2 and CSN1 S,involved in the positive regulation of lipid metabolism,were significantly down-regulated,too.This indicates that selenium reduced the acute phase response and lipid metabolism.Study II: The contents of HRG,LBP and SAA3 were tested by ELISA.The results showed that HRG(96.41±19.79?g/ml vs 61.68±13.25?g/ml,P < 0.05),SAA3(3.21±0.84 ?g/ml vs 6.37±1.36 ?g/ml,P < 0.01)and LBP(209.46±40.53 ng/ml vs 421.63±60.87 ng/ml,P < 0.01)were significantly regulated,which indicated that the iTRAQ results were accurate and reliable.Conclusion: Supplement of selenium yeast in prenatal caused 48 proteins of the cows plasma significantly differentially expressed in parturition.The results of GO analysis and enrichment suggested that the supplement of selenium yeast during the prenatal period could alleviate inflammation and reduce lipid metabolism,which is conducive to the control of postpartum infectious diseases,ketosis and fatty liver.