Histology Of Ovarian Follicles And Identification Of SNPs Related To Egg Production In Different Goose Breeds

Goose egg production,as a crucial economic trait in goose production,is not only related to the economic benefits of breeding,but also closely related to the development and growth of the goose industry.The egg production of different goose breeds varies greatly.The annual egg production of high yielding breeds can reach more than 70,while the annual egg production of low yielding breeds is only about 20 eggs.In order to reveal the reasons for the differences in egg production performance of different goose breeds,this study was focused on the differences in ovarian histology and reproductive hormone secretion among different goose breeds,namely Yangzhou goose,Zhejiang White goose and Carlos goose.The gene frequency distribution of SNPs locus related to egg production among different breeds were then analyzed to further identify the effect of SNPs mutation sites on egg production in geese.The purpose of the study was to reveal the causes of differences in egg production performance of different goose breeds,and to provide some reference for improving egg production performance in geese.The main findings were as follows:1.In order to reveal the differences in egg production performance of different goose breeds from ovarian histology,the morphological structure of ovarian follicles of different goose breeds during the egg production period was observed.The results showed that the hierarchical follicles of Yangzhou geese were generally 5-6 pieces,and Zhejiang White goose and Carlos goose generally have 3 to 4 pieces.In terms of the number of hierarchical follicles,Zhejiang white goose is the highest,reaching 69-75 pieces,followed by Yangzhou goose and Carlos goose.The paraffin section results showed that the thickness of the granular layer of SWF,LWF,SYF and LYF follicles in Yangzhou goose were 13.62 ± 0.89?m,20.53 ± 1.35?m,22.50 ± 1.44?m,24.69±1.30?m,respectively,which were significantly higher than those of the other two geese,which shows that the level of egg production in goose depends on the number of hierarchical follicles and the thickness of granular layer of prehierarchical follicles.At the same time,ELISA kits were used to test the reproductive hormones of all breeds.The results showed that FSH remained at a certain concentration(16.82?20.11 U/L)during prehierarchical follicular development.The amount of LH in Yangzhou goose LYF was 884.17 ± 39.44 pg/mL,which was significantly higher than Zhejiang White goose(503.09 ± 34.76pg/mL)and Carlos goose(485.56 ± 16.17 pg/mL).The PROG content of Yangzhou goose rapidly increased after entering the LWF period,which was significantly higher than that of Zhejiang White goose and Carlos goose and it lasted until the LYF period.Above all,the high-secretion of LH and PROG promotes prehierarchical follicles development.2.In order to reveal the differences in egg production performance of different goose breeds from the molecular level,the key candidates genes MAGI-1,KIAA1462,ARHGAP21,ACSF2 and ASTN2 were investigated as subjects and gene frequency distributions in different goose breeds were analyzed.As the result,the gene frequency distribution of ACSF2 gene at the Record-106582 site varied the most,and the frequency of A gene in Yangzhou goose was significantly higher than that of Carlos goose,indicating that the difference in A gene frequency may be one of the reasons for the difference in egg production of different goose breeds.3.To further verify the functions of SNPs of egg laying candidate genes,the MAGI-1 gene Record-106975 site and ACSF2 gene Record-106582 site were selected as candidate sites.Real-time quantitative PCR was used to detect the expression levels of different genotypes.The results showed that the mRNA expression of AG genotype(1.87 ± 0.37)in MAGI-1 gene was significantly higher than that in AA genotype(1.01 ± 0.33)and GG genotype(1.00 ± 0.35).There was no significant difference between AA genotype and GG genotype.CC genotype(1.11± 0.07)of ACSF2 gene was significantly higher than AA genotype(1.00 ± 0.04)(P<0.05),while AA genotype was significantly higher than AC genotype(0.65 ± 0.04).Functions of the transcription factor binding sites before and after mutation was analyzed by EMSA.The results showed that the ACSF2 gene Record-106582 A>C site affected transcription factor cis-acting elements,resulting in high expression of the ACSF2 gene CC genotype,indicating that the SNP sites are related to laying performance.In summary,the level of egg production mainly depends on the number of hierarchical follicles and the thickness of the pre hierarchical follicle granular layer,and the ACSF2 gene Record-106582 A>C mutation is also related to laying performance.