The Relationship Between Liver Function,DNA Methylation And Egg Laying Rate In Laying Hens

In order to study the relationship between liver function and Hy-line Brown layers with different laying rate,the relationship between liver genome methylation level and Hy-line Brown layers with different laying rate.We observed and analyzed the liver function of laying hens with different week ages and different laying rate,the whole genome methylation of laying hens with different laying rate.About the liver function,we detected the lipid metabolism,oxidative stress,endoplasmic reticulum stress and immune stress.The whole genome methylation of liver was analyzed from the aspects of the construction of whole genome DNA methylation map,the methylation level of the whole genome,the differential methylation gene,the GO annotation and the enrichment of KEGG pathway.In Experiment 1,we investigated the liver function of hens with different weeks of age.Sixteen Hy-line Brown layers with high laying rate were selected and assigned to two groups: higher laying rate with 25 weeks age,high laying rate with 85 weeks age.The results showed that the two groups of hens had no difference in serum levels of lactate dehydrogenase,aspartate aminotransferase,alkaline phosphatase,total protein,serum albumin,triglyceride,total cholesterol,alanine aminotransferase.The hens of 85 weeks had higher level of glucose in serum,lower level of SOD in liver.In Experiment 2,we investigated the liver function of hens with different laying rate.Twenty-four 85-weeksHy-line Brown layers of 85 weeks age were divided into three groups: high laying rate(100%),middle laying rate(70%-80%),low laying rate.The results showed that the serum level of alkaline phosphatase and glucose were a downward trend in the low laying rate hens.The middle laying rate hens had lower level of CAT and higher level of protein carbonyl,had lower ACC and FAS m RNA expression levels,higher LXR mRNA expression levels in the liver compared to the other groups of hens.The low laying rate hens had higher level of triglyceride,lower TNF-? mRNA expression levels in the liver compared to the other groups of hens.In Experiment 3,we investigated the Whole genome methylation analysis in the liver of hens with different laying rate.Sixteen Hy-line Brown layers with different laying rate were divided into two groups: high laying rate(100%),low laying rate(40%-60%).The whole genome methylation was analyzed by bisulfite sequencing.The results of C methylation level,respectively,in different chromosomes,different gene regions and different gene original regions were higher than those in high laying rate group.A total of 3155 differentially expressed genes were identified by DMR(differential methylation region),of which are 2172 up regulated genes and 983 down regulated genes.In upstream and CDS regions,there are 18 GO term were significantly enriched by functional enrichment analysis,and 3 pathway were significantly enriched in KEGG pathway(P < 0.05): purine metabolism,glycerophospholipid metabolism and pentose phosphate pathway.The low laying rate hens had low methylation level of ATIC gene in CDS region and high mRNA expression level in liver;The low laying rate hens had high methylation level of ALDOB gene in CDS region and high mRNA expression in liver.The low laying rate hens had high LCPT1 and LXR mRNA expression levels in liver.Based on the above results,there were no significant differences in the liver function indexes of laying hens with high laying rate at different week ages,but there were significant differences in the liver function and the whole genome methylation between the laying hens with different laying rate at the same week ages.