Regulation Of Synthesis And Metabolism Of Fatty Acids Under The Stress Of Mastitis In Dairy Cow

Mastitis in dairy cow is one of the most frequent and important diseases in the dairy industry worldwide with great economic losses to the dairy industry. Most researchers have managed to prevent and control mastitis in cow through immunization but with no effect. The way through genetic and breeding technology(mastitis resistant selective breeding) with the aid of veterinary technology and management in nutrition and sanitation is recognized as a sound solution to the mastitis in cow. Recent researches demonstrate that infection by pathogenic microbes is the major cause of mastitis in cow, and Staphylococcus aureus is one of them. S. aureus is highly pathogenic, with its production of many toxins and enzymes, including enterotoxin, leucocidin, and hemolysin. In this study, the dynamics of fatty acids content in milk induced by recessive mastitis was first exposed, moreover, the relationship between polymorphism of SCD1, the key gene of synthesis and metabolism of fatty acids, and fatty acids content in milk was pinpointed and analyzed. In further research, S. aureus was administered to infect the mammary of Holstein cow, and the systemic reaction was monitored. Based on clinical diagnosis, identification of germs and pathogenic test in mammary tissues, the animal model of mastitis was successfully constructed. The Agilent expression spectrum chip assay was then used to compare the difference in gene expression between artificially S. aureus infected mammary and control, and through GO and Pathway analysis to establish the regulation network of synthesis and metabolism of fatty acids. Quantitative PCR was conducted to verify the results.Based on the above work, the effect of mastitis on milk component like the ingredient of fatty acids were further explored, and would provide data for selection of effective genetic markers of the ingredient of fatty acids in milk.1.154Holstein cows from scale dairy farms in Yangzhou were sampled as subjects. All cows were executed mastitis test by BMT method. The results showed that46were healthy,37were "+"positive,31were "++"positive,40were "+++" positive. Comparison of22ingredient of fatty acids among different level of mastitis positive and healthy cows indicated that, with the increases of severeness of recessive mastitis, the content of fatty acids C14:1, C15:0and C15:1changed significantly. Comparison in indices of C14, C15, C16, C18and C24, SFA, MUFA, PUFA, MCFA and LCFA exposed that C14index, C15index, SFA and MUFA were highly/significantly different between healthy and positive group of certain degree.2.323blood samples and140milk samples were collected from323Holstein cows of Yangzhou University Experimental dairy farm to explore the effect of the polymorphism of SCD1ex on5on the content of unsaturated fatty acids and unsaturated index. Results showed that SCD1-T762C and SCD1-C878T were polymorphic, with A (0.7897) and C (0.7835) as the advantageous allele, respectively. Moreover, significant linkage disequilibrium was observed between SCD1-762and SCD1-878with a coefficient of0.8799(r2).Significant effects of SCD1-762and SCD1-878polymorphisms were observed on MUFA and total unsaturated coefficient, which inferred that SCD1could be used as an important candidate genetic marker for further research in selective breeding for certain fatty acid component.3.Through administering S. aureus to infect the mammary of Holstein cow, the animal model of mastitis was successfully constructed. Changes in the ingredient of fatty acids before and after infection were then explored. The results showed that palmic acid (C16:0) had a highest portion of more than30%, and oilic acid took up more than20%, while long-chain PUFA like C20:2and C20:3occupied a low portion. A significant decrease in content of C22:6was observed after infection of S. aureus. The S. aureus infection also exerted significant effects on C20index, content of MUFA, PUFA and mc-FA. 4. The Agilent expression spectrum chip assay screened out3271genes differentially expressed between infected and control, among them2057upregulated and1214downregulated. Go analysis exposed that257participated in certain Biological Process, including41associated with Cellular Component and73with Molecular Function. Pathway analysis indicated22significant pathway. Three pathways associated with Fatty acids were selected, Fatty acid metabolism, Biosynthesis of unsaturated fatty acids, Fatty acid biosynthesis. For these three pathways,15differentiated genes were found,6upregulated (DGAT2, SLC27A6, FABP2, FADS2, PLP1, SCD) and9downregulated (ACAT2, ELOVL5, PAPPA, ACOX3, ALDH3A2, EHHADH, FASN, LPL, SREBF1).10of these differentiated genes were verified between infected and control group with results relatively identical with that of the Agilent expression spectrum chip assay. The regulation network of synthesis and metabolism of fatty acids was then established.