Analysis Of Reproductive Traits And Selection Methods Of Etong Two-end-black Pig

ETong two-end-black pig is a new breed bred from crossbreeding between the large white pig and the Tongcheng pig,the reproductive traits are the breeding target traits of the breed.In this study,the ETong two-end-black pig are used as the subjects of the study,comprehensively measuring and analyzing the reproductive traits of the ETong two-endblack pig,construct the breeding value model of total number of born,select total number of born and teat number respectively.At the same time,A genome-wide association analysis(Genome-wide association study,GWAS)is also performed to screen for candidate genes and molecular markers affecting teat number,to provide a scientific basis for the selection and retention of reserve pigs and improvement of reproductive traits in ETong two-endblack pig.the main results of this study are as follows:1.Determination and analysis of reproductive traits of the ETong two-end-black pig.In this study,11 reproductive traits including the total number of born,the number of born alive,the teat number and so on,are measured,recorded,collated and statistically analysed,a total of 265 litters are collected for reproductive traits.Statistically obtained,the total number of born for the first parity is 11.8,the total number of born for the second parity is 12.5 and the total number of born for the third parity and above is 12.6 for the ETong two-end-black pig;analysis identified parity,season of parturition and month of mating as non-genetic factors influencing reproductive traits.Parity significantly impact the total number of born,the number of born alive,the litter weight at birth,the average weight of born individuals,the litter weight at 21 days and the weaning litter weight of the ETong two-end-black pig.The season of parturition significantly influence the litter weight at birth and the average weight of born individuals of the ETong two-end-black pig;month of mating significantly influence the number of born alive,the litter weight at birth,the average weight of born individuals,the litter weight at 21 days and the weaning litter weight.2.Modelling of total number of born for breeding value estimation and seed selection.Breeding values for total number of born estimate using information on information on all relatives of the individual.Only parity had a significant effect on the total number of born,as determine by the wald test for season,month and parity.Using lineage and phenotypic value information estimate heritability of the total number of born of ETong two-end-black pig is 0.09,and standard error is 0.08.using parity as a fixed effect,individual additive effects and mated boars as random effects,to construct the model of estimate the breeding value of total number of born.The average accuracy of the estimated breeding values is0.52.The results of selection and retention using both breeding values and large litter selection are consistent.3.Phenotypic selection for teat number.The breeding pigs with a teat number greater than 7 pairs are selected,after a generation of choices,analysis a selection response is 0.11,a realistic heritability is 0.52 for teat number,the three heritabilities estimated indicate that the teat number is high heritability traits.4.Genome-wide association analysis to screen for SNP and candidate genes significantly associated with teat number.Using GCTA’s MLMA model,with significance thresholds of P=1.0E-7,the recommended threshold setting is P=1.0E-6,and GWAS analysis of the left teat number,right teat number and total teat number of 149 ETong twoend-black pig,there are 38 Single nucleotide polymorphisms(Single nucleotide polymorphisms,SNP)exceeding the significance threshold of 1.0E-6 that have a significant effect on teat number,locate mainly on SSC1(Sus scrofa chromosome,SSC),SSC2,SSC5,SSC6,SSC8,SSC9,SSC13 and SSC15.10 SNP that are significantly associated with left teat number,11 SNP that are significantly associated with right teat number,and 17 SNP that significant with total teat number,the screening yielded candidate genes,including FGF7,MAPK9,ARSB,CAVIN2,DYRK2,THBS4,BMPR1 A,PDIA6 and MAP9,which may be significantly associated with teat number traits in ETong two-endblack pig.In summary,In this study,a comprehensive analysis is carried out to determine and statistically analyse nine reproductive traits of ETong two-end-black pig,Selection and phenotypic selection for total number of born and teat number,respectively,achieving the desired results;and by GWAS,SNP and candidate genes affecting the teat number are identified.This study provides a scientific basis for the further development of breeding plans and programmes for the ETong two-end-black pig,the selection and retention of ETong two-end-black pig reserve pigs and the improvement of breeding traits.