Establishment Of Selection Index And Application Of Genome Selection For Holstein Cows In Xinjiang Hutubi Herd Farm

Comprehensive selection index is one of the most effective methods for livestock and poultry selection.With the introduction of the concept of "balanced breeding",breeders around the world have found that the breeding of dairy cows based solely on milk production traits will lead to the degradation of reproductive performance and other problems.Therefore,more and more functional traits are included in the comprehensive selection indexes of countries around the world.The comprehensive selection index revised in China in 2020 included milk fat content,milk protein content,somatic cell score,feet and leg score,mammary system score and type total pointsl score,but did not consider functional traits such as reproduction.Based on China’s current comprehensive selection index,this study took six subordinate pastures of Xinjiang Hutubi Herd Farm as follows:305 d milk yield,milk fat percentage,milk protein percentage and somatic cell score were used as milk producing traits based on breeding records and calving records from 1985 to 2021,DHI determination records from 2008 to 2021 and body appearance identification records from 2021.Calving interval and age at first calving were reproductive traits.feet and leg score,mammary system score and type total pointsl score were type traits.SAS 8.1 software was used to analyze the influence of non-genetic factors on each trait.Non-genetic factors that had significant effects on each trait were used as fixed effects in the subsequent heritage evaluation model.DMU software was used to estimate the variance components of each trait with animal model and repeatability model,and genetic parameters and breeding values were calculated.The marginal benefit of each target trait was calculated by the difference method,and the comprehensive selection index of Holstein cattle in Xinjiang was constructed according to the marginal benefit and genetic standard deviation of each trait.357 reserve cows were genotyped using Illumina 100K SNP chip,and the genomic breeding values of milk producing traits of 357 reserve cows were calculated by one-step method and GCPI2.The main results are as follows:(1)The estimated heritability of 305 d milk yield,milk fat percentage,milk protein percentage and somatic cell score were 0.19,0.16,0.20 and 0.06,respectively,and the repeatability was 0.42,0.23,0.20 and 0.10,respectively.The heritability of calving interval and age at first calving was 0.06 and 0.28,respectively,and the repeatability of calving interval was 0.14.The heritability of feet and leg score,mammary system score and type total pointsl score were 0.04,0.31 and 0.07,respectively.(2)According to the pasture production management and the parameters of the market economy and genetic parameter estimation,target traits determine 305 d milk yield,milk fat percentage,milk protein percentage,somatic cell score,calving interval and age at first calving,feet and leg score,mammary system score and type total pointsl score for the xinjiang region size holstein cattle breeding target characters,and calculate the various characters marginal benefit value,The relative economic importance of milk producing traits,reproductive traits and body shape traits was 58%,12%and 30%,respectively.Breeding traits and body shape traits were taken as breeding target traits to ensure that the improvement of milk production performance in the dairy cattle heritage improvement process would avoid the decline of other performance,which laid a foundation for the development of the concept of"balanced breeding" in our area and provided basic parameters for the subsequent construction of comprehensive selection index.(3)Construction of Holstein cattle comprehensive selection Index in Xinjiang:CPIXJH=50×ENMY/997.46+4EBFP/0.20+3×EBPP/0.09-EBSCS/0.37-10×EBCI/22.47-2×ENAFC/2.26+8×EBFL/0.70+8×EBMS/0.27+14×EBType/0.43(4)Xinjiang region Holstein cattle 305 d milk yield,mammary system and type pointsl the genetic tendency of total score rise,butterfat rate and the rate of protein showed a trend of contrary,creamy rate of decline,protein rate is rising,the somatic cell score are slowly rising trend,calving interval,first-timer months and limb hoof presents obvious downward trend.The inheritance trend of different traits reflected the effect of genetic improvement of Holstein dairy cows in our region for many years,and also provided reference for subsequent breed selection and matching.(5)The formula of Comprehensive selection Index(CPIXJH)of Holstein cows in Xinjiang Hutubi Herd Farm was constructed to calculate the CPIXJH value of Holstein cows in the herd.The mean value of CPIXJH of Holstein cows in the herd was 15.71,and the top 3000 cows were selected as the high-yield core group.A total of 640,430,699,447,199,and 585 cows on farms 1,2,4,5,6,and 7 were included in a high yield core herd of 3000 cows,respectively.(6)Based on the genetic evaluation of 357 Holstein reserve cows based on genomic information,the breeding values of milk producing traits were calculated,and combined with GCPI2,the average genome comprehensive breeding value of 357 reserve cows was 1834.42,and 8 of the top 20 reserve cows were all descendants of HOCHNM11112651 bull.To sum up,this study Xinjiang Hutubi Herd Farm wall as the research object,through regular and genome genetic evaluation and the construction of comprehensive selection index,breeding value,calculate the 357 reserve cow genome for Xinjiang Hutubi Herd Farm build a core group of 3000 head of high yield,but also for the establishment of our precise matching,breeding plan and improve the level of dairy production performance to provide the reference.