Genome-Wide Association Study For Fatty Liver Resistance In Periparturient Dairy Cows

Fatty liver is an important metabolic disease of dairy cows during perinatal period.The occurrence of fatty liver in dairy cows is related to the management,nutrition and genetics of dairy cows.It affected the health of dairy cows seriously,resulting in dystocia,multiple diseases,infection and other problems,it can also decline the milk production,make the calving interval prolonged.Therefore,we need to enhance the disease resistance of fatty liver of dairy cattle population and cultivate resistant varieties.In order to find out the cow’s fatty liver resistance SNPs and disease resistance candidate genes,we performed GWAS on fatty liver trait in 399 cows,it can also provide some basic data for molecular genetic breeding cows.Twenty Holstein cows were selected,whose age parity and health status is similar,Serum samples were collected at 5 time points.We tested the content of NEFA,Glu and AST.The equation(Y=-0.51-0.0032NEFA+2.84Glu-0.0528AST)was used to calculate the Y value.The incidence of fatty liver in dairy cows was determined according to Y value,it was found that the incidence rate of fatty liver was the highest at tenth day after delivery,which was consistent with the results of many studies.Therefore,we used the tenth day after delivery for the sampling time of whole genome association study.Serum samples were collected at tenth days after delivery of the 454 cows,we tested the content of NEFA,Glu,AST,TG,TCHO and ALP.The equation(Y=-0.51-0.0032NEFA+2.84Glu-0.0528AST)was used to calculate the Y value.The dairy cows were divided into two groups: fatty liver susceptible group(case)and fatty liver resistance group(control).The whole genome association study was performed based on case-control study.At the same time,the biochemical indexes were also performed based on case-control study.Bonferroni multiple testing was adopted to adjust the results of association analysis on each chromosome level.In the GWAS of Holstein and total population,the four SNPs reached significant level of chromosome in each population.The GWAS of NEFA,Glu and AST in Holstein and total population,6/12,0/1,6/6 SNPs were detected significantly at level of chromosome.VRK1,SLC24A4,RGS2,C9,ZGRF1 are associated with the liver disease,carbohydrate metabolism,lipid metabolism,inflammation and immune response,which may be involved in the formation of fatty liver.However,the genes further functional verification is needed.This study has completed the analysis of genome-wide association of fatty liver diseaseresistance,and screened seven significant SNPs related with fatty liver susceptibility and resistance.Seventeen significant SNPs were related with biochemical indexes.We found that five possible candidate disease resistance gene.This study provides a basis of verification and analysis for the next step of gene function.At the same time,it also provides some SNPs data for marker assisted selection of herd genetic research.