Using Proteomic To Analyzing The Effects Of Heat Stress On Performance In Dairy Cows

Based on the proteomics and bioinformatics methods,this study revealed the mechanism of the effect of heat stress on the mammary gland and liver of dairy cows by comparing the proteomic changes in the dairy cows under heat stress and heat stress-free.The main research contents and results are as follows:1.The effect of heat stress on the production performance of dairy cows:12 healthy Holstein cows were randomly divided into two groups.The basic diet of the experiment is the existing diet of the pasture to meet the basic nutritional needs of lactating dairy cows.The results showed that heat stress significantly reduced feed intake,milk yield and milk protein content of dairy cows,while the number of somatic cells in milk increased significantly.2.Proteomics analysis of mammary gland tissue in cows under heat stress:In this experiment,the proteome of mammary gland of six cows under heat stress and heat stress-free were compared and analyzed by liquid chromatography mass spectrometry(LC-MS)/MS-dependent.The results showed that a total of 4,889 proteins were identified in the two groups,69 of which were differentially expressed in mammary gland tissues of the two groups.Down-regulated proteins in mammary gland tissues of the heat stress group were mainly involved in protein initiation translation and tRNA aminoacylation in biological processes.At the same time,up-regulated proteins in mammary gland tissues under heat stress are mainly manifested in alleviating tissue damage caused by heat stress.Western blot results showed that Calumenin(CALU)and casein(CSN2)were significantly higher in the heat stress group(P<0.05).Meanwhile,the protein eukaryotic initiation factor 4a-I(EIF4A1)and leucapyl-tRNA synthase(LARS)related to the protein translation process in the heat stress group were significantly higher than those in the heat stress-free group(P<0.05).3.Proteomics analysis of liver tissue in dairy cows under heat stress:In this experiment,the proteome of six cow livers in the heat stress group and the heat stress-free group were compared and analyzed by LC-MS/MS.The results showed that the total of 2448 proteins were identified in the whole proteomics of cow liver,among which 86 proteins were differentially expressed in the two groups,mainly involved in the processes of electron transport chain,protein folding,glyoxylate and dicarboxylate metabolism.The results of western blot indicated that the expression of heat shock protein 10(HSPE1),electron transfer flavoprotein subunit beta(ETFB)and citrate synthase(CS)in the heat stress group was significantly higher than that in the heat stress-free group(P<0.05).However,the expressions of NADH dehydrogenase flavoprotein 1(NDUFV1)and glucose-6-phosphatase(G6PC)in the heat stress group were significantly lower than the heat stress-free group(P<0.05).In summary,heat stress resulted in feed intake,milk yield,milk protein content decreased significant and the number of somatic cells increased significant.Heat stress affected the oxidative phosphorylation process of mitochondria in the liver tissue of dairy cows,inhibited the translation initiation and aminoacyl-tRNA biosynthesis in the breast tissue of dairy cows,resulting in a decrease in milk protein synthesis.Dairy cow liver relieves heat stress by increasing the expression of molecular chaperone protein.And,the mammary gland by enhancing the expression of RNASE4,CDH1 and CALU proteins,reduce heat stress on tissue damage.