| Egg weight not only affects the uniformity of chicken seedlings but also the sales of eggs.However,in the laying period of laying hens,there is a problem of smaller laying in the early stage and larger laying in the late stage.Therefore,the concept of"egg weight increase"was proposed in this experiment,and the molecular mechanism of egg weight increase was studied to achieve the goal of"not too small eggs in the early stage and not too big eggs in the late stage".C3and C4 laying hens were selected for the experiment,and their body weight,laying day,laying egg weight,heritability of some characters,and egg quality at 24,32,and 40 weeks of age were measured respectively,and the weight and laying rate were fitted.Measurements were taken of the body size of C3 and C4 strains at32 weeks of age and 30 weeks of age,as well as egg weight at 26-44 weeks of age and24-44 weeks of age.According to the"egg weight increase",C3 and C4 were divided into high,middle and low groups.The differences in body size,ovary,fallopian tube and other traits of the C3 high,middle and low groups were analyzed.Additionally,the ovarian and magnum transcriptomes were analyzed for the high and low groups of C3.The results are as follows:(1)The R~2 of the Gompertz model of C4 laying hens was 0.994,and the coefficient of variation of body size traits was less than 10%.The opening age of the C4 line was 143.05days,and the opening egg weight was 41.43g.At 24 and 44 weeks of age,the egg weight was 49.84g and 57.05g,and the heritability was 0.40 and 0.40,respectively.The increase of egg weight was 0.07,and the maximum increase of egg weight was 54.69%and 23.33g during 24-44 weeks.(2)The Von-Bertalanffy model had the best fitting effect(R~2=0.993),which was closer to the actual body weight of laying hens at 32 weeks of age(1375.81g).C3 was 168.09days old,the weight of the first laying eggs was 33.11g,and the proportion of yolk at different weeks increased from 0.29 to 0.33.At 26 and 44 weeks of age,the egg weight was 36.64g and 45.61g,and the heritability was 0.30 and 0.55,respectively.The heritability of egg weight increase was 0.10,the maximum increase was 58.62%and the maximum increase was 18.00g.The increase of C3 egg weight was significantly higher than that of high and low groups in yolk weight,egg white weight and number of grade follicles,and the difference in ovarian weight between high and middle groups and low groups was extremely significant.(3)According to the analysis of the ovarian transcriptome of C3 laying hens,278differentially expressed genes were found in the ovaries of the high-laying hens;45 genes were up-regulated,233 genes were down-regulated,and they were enriched in the"Wnt signaling pathway"and"adhesion linkage"pathways,compared with the low-egg weight gain group.FST,INHBB,SRC,STAR,HAS2 and other differential genes were found to be related to follicle maturation.(4)A total of 1326 differentially expressed genes were detected in the dilatation tissues of C3 lines by transcriptome sequencing.Compared with the group with low egg weight increase,917 genes were up-regulated and 409 genes were down-regulated,which were enriched into pathways such as"energy metabolism"and"mitochondria".ST3GAL2,CDH4,Smad5,ITGA7 and other genes were screened,which were speculated to be involved in egg white synthesis and secretion. |
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