SNP (Single Nucleotide Polymorphism) molecular marker related to peak daily milk quantity character of dairy cow and application of SNP molecular marker

Abstract

The invention belongs to the technical field of molecular biology, and relates to an SNP (Single Nucleotide Polymorphism) molecular marker related to peak daily milk quantity traits of dairy cows and application. Mainly discloses five SNP (Single Nucleotide Polymorphism) molecular markers (SEQ ID NO.1-5) which are obviously related to the peak daily milk quantity character of the Chinese Holstein cattle. Whole genome association analysis and identification show that the markers can be used for molecular marker-assisted breeding of Chinese Holstein cattle. The five SNP loci are detected in actual breeding, seed selection and matching can be guided, the breeding strategy is optimized, and the population genetic progress is accelerated. The traditional breeding bottleneck is broken through, the seed selection accuracy and efficiency are remarkably improved, the genetic improvement process of high-yield cows is accelerated, and milk enterprises are assisted to improve economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of molecular biology technology and relates to SNP molecular markers and their applications that are related to peak daily milk yield traits in dairy cows. Background Technology

[0002] Dairy farming, as an important part of agriculture, provides humanity with abundant dairy resources. In the dairy farming industry, milk production, especially peak daily milk yield (PM), is one of the core economic traits for measuring dairy cow productivity and plays a decisive role in the economic benefits of farms. Increasing peak daily milk yield not only increases total milk production but also improves farming efficiency, reduces unit costs, and enhances market competitiveness.

[0003] Dairy cows have a relatively long reproductive cycle and long generation intervals. Traditional breeding methods based on pedigrees and phenotypic performance require a significant amount of time and effort to select superior individuals, resulting in slow genetic progress and failing to meet the urgent demand for high-yielding dairy cows in the rapidly developing dairy industry. With the rapid development of molecular biology techniques, new directions and methods have been provided for dairy cow breeding. Through research and intervention at the gene level, it is hoped that precise regulation of high-quality dairy cow breeding can be achieved, improving breeding efficiency. Among numerous molecular genetic studies, single nucleotide polymorphisms (SNPs), as third-generation genetic markers, are widely present on chromosomes of species genomes. Some SNPs located within genes can directly affect protein structure or expression levels, leading to phenotypic differences, making them an important entry point for studying the genetic mechanisms of milk production traits in dairy cows.

[0004] Currently, the closest existing technologies to this invention mainly focus on the research and application of molecular markers related to dairy cow milk production traits. Some studies have identified certain SNP molecular markers associated with dairy cow milk production traits using techniques such as genome-wide association analysis. For example, some studies have identified a specific SNP locus located on chromosome 19 of the dairy cow genome that is associated with milk production traits. By detecting the genotype at this locus, heterozygous individuals are eliminated, and homozygous individuals are retained, with the aim of improving the milk quality of offspring dairy cows. Other studies have discovered SNP molecular markers affecting lactation performance in the NCOA6 gene of dairy cows. Using these markers for marker-assisted breeding can improve the lactation performance of dairy cows to a certain extent.

[0005] However, existing technologies still have many shortcomings. Most of the identified SNP molecular markers associated with milk production traits are not specifically targeted at the key trait of peak daily milk yield in dairy cows. Their impact mechanisms and effects on peak daily milk yield are not thoroughly studied, making it impossible to accurately screen for dairy cows with high peak daily milk yield potential using these markers. While existing genomic selection technologies have made progress in the genetic assessment of overall milk production traits, they are essentially estimates based on existing data. Limited by factors such as the amount of phenotypic data, model construction, and prior assumptions, the accuracy of predicting the complex trait of peak daily milk yield in dairy cows still needs improvement. Current technologies lack a complete, efficient, and specific SNP molecular marker screening and application system for peak daily milk yield in dairy cows, making it difficult to meet the urgent needs of actual production for increasing peak daily milk yield.

[0006] Genome-wide association studies (GWAS) are an effective tool for identifying quantitative trait loci (QTLs) of important economic traits in dairy cows. Existing studies mostly utilize GWAS methods combined with specific gene biological functions to select candidate genes and SNPSs that significantly influence various traits in dairy cows. This method can narrow down the search area and improve accuracy, contributing to the discovery of functional genes and providing direction for dairy cow genetic breeding. Summary of the Invention

[0007] The purpose of this invention is to address the aforementioned problems by providing a SNP molecular marker associated with peak daily milk yield in dairy cows and its application. This invention analyzed the peak daily milk yield (PM) of 380 Chinese Holstein cattle from 2015 to 2023. The average PM was 45.02 kg (standard deviation 14.33 kg), exhibiting moderate heritability (0.20). Based on whole-genome sequencing data and GWAS analysis, candidate variant sites associated with peak daily milk yield (PM) in dairy cows were identified, providing "precise targets" for high-yield dairy cow breeding, breaking through traditional breeding bottlenecks, improving the accuracy and efficiency of selection, accelerating the genetic improvement process, and helping dairy companies improve economic benefits.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] SNP molecular markers associated with peak daily milk yield in dairy cows include at least one of the following markers:

[0010] Marker 1: Located at 113000819 bp on chromosome 6 of the bovine genome ARS-UCD2.0 version, the base at this site is G or A, corresponding to the 51st nucleic acid site in SEQ ID NO.1 of the nucleic acid sequence listing;

[0011] Marker 2: Located at 87592639 bp on chromosome 11 of the bovine genome ARS-UCD2.0, the base at this site is G or A, corresponding to the 51st nucleotide site in SEQ ID NO.2 of the nucleic acid sequence listing;

[0012] Marker 3: Located at 43,988,976 bp on chromosome 22 of the bovine genome ARS-UCD2.0, the base at this site is G or A, corresponding to the 51st nucleotide site in SEQ ID NO.3 of the nucleic acid sequence listing;

[0013] Marker 4: Located at 43989144 bp on chromosome 22 of the bovine genome ARS-UCD2.0, the base at this site is G or A, corresponding to the 51st nucleotide site in SEQ ID NO.4 of the nucleic acid sequence listing;

[0014] Marker 5: Located at 43990890 bp on chromosome 22 of the cow genome ARS-UCD2.0, the base at this site is G or A, corresponding to the 51st nucleic acid site in SEQ ID NO.5 of the nucleic acid sequence listing.

[0015] The present invention also provides an application of the above-described SNP molecular markers in the selection or assisted selection of dairy cow breeds or strains with peak daily milk yield traits, specifically for the selection or assisted selection of dairy cows with high / low peak daily milk yield.

[0016] This invention also provides a method for breeding or assisting in the selection of dairy cow breeds or strains related to peak daily milk yield using the SNP molecular markers described above, the specific steps of which are as follows:

[0017] Genomic DNA was extracted from dairy cows, and nucleotide sequence at position 113000819 of chromosome 6 was detected. If the sequence at position 113000819 was G or A, the genotype of the dairy cow to be tested was determined to be AG, AA, or GG. AG-type cows were selected for further selection and / or breeding as needed. The peak daily milk yield of AG-type cows was higher than that of AA-type cows.

[0018] Genomic DNA was extracted from dairy cows, and nucleotide 87592639 of chromosome 11 was detected. If the sequence of nucleotide 87592639 was G or A, the genotype of the dairy cow to be tested was determined to be GA, AA, or GG. Dairy cows with the GA genotype were selected for further selection and / or breeding as needed. The peak daily milk yield of the GA genotype dairy cows was higher than that of the AA genotype dairy cows.

[0019] Genomic DNA was extracted from dairy cows, and nucleotide 43,988,976 of chromosome 22 was analyzed. If the sequence of nucleotide 43,988,976 was G or A, the genotype of the dairy cow was determined to be GA, AA, or GG. GA-type cows were selected for further selection and / or breeding as needed. The peak daily milk yield of GA and / or GG-type cows was higher than that of GA-type cows.

[0020] Genomic DNA was extracted from dairy cows, and nucleotide 43,989,144 of chromosome 22 was analyzed. If the sequence of nucleotide 43,989,144 was found to be G or A, the genotype of the dairy cow to be tested was determined to be GA, AA, or GG. GA-type cows were selected for further selection and / or breeding as needed. The peak daily milk yield of GA and / or GG-type cows was higher than that of AA-type cows.

[0021] Genomic DNA was extracted from dairy cows, and nucleotide 43,990,890 of chromosome 22 was detected. If the sequence of nucleotide 43,990,890 was G or A, the genotype of the dairy cow to be tested was determined to be GA, AA, or GG. Dairy cows with the GA genotype were selected for further selection and / or breeding as needed. The peak daily milk yield of the GA and / or GG genotype dairy cows was higher than that of the AA genotype dairy cows.

[0022] To further clarify, the genotype GG or AA in the cow's chromosome 6 represents a homozygous individual with nucleotide G at position 113000819 or a homozygous individual with nucleotide A.

[0023] The genotype GG or AA in the 11th chromosome of the dairy cow represents a homozygous individual with nucleotide G at position 87592639 or a homozygous individual with nucleotide A at position 87592639, respectively.

[0024] The genotype GG or AA in the 22nd chromosome of the dairy cow represents a homozygous individual with nucleotide G at position 43988976 or a homozygous individual with nucleotide A at position 43988976, respectively.

[0025] The genotype GG or AA in the 22nd chromosome of the dairy cow represents a homozygous individual with nucleotide G at position 43989144 or a homozygous individual with nucleotide A.

[0026] The genotype GG or AA on chromosome 22 of the dairy cow indicates a homozygous individual with nucleotide G at position 43990890 or a homozygous individual with nucleotide A at position 43990890, respectively.

[0027] The present invention also provides an SNP genotyping detection kit, comprising specific primer pairs and / or probes for amplifying or detecting the five SNP sites described above, wherein the amplification region covers the 51st SNP site in the sequence shown in SEQ ID NO:1-5.

[0028] By adopting the above technical solution, the present invention has the following beneficial effects:

[0029] This invention, for the first time based on a genome-wide association analysis (GWAS) of 380 Chinese Holstein cattle, identified five SNP molecular markers significantly associated with the peak daily milk yield (PM) trait in Chinese Holstein cattle. These markers were found in the LOC107132586 gene on chromosome 6 (g.113000819A>G, AG genotype has the highest breeding value for peak daily milk yield (PM)), the GRHL1 gene on chromosome 11 (g.87592639G>A, GA genotype has the highest breeding value for PM), the IL17RD gene on chromosome 22 (g.43988976G>A, GA genotype has the highest breeding value for PM), the IL17RD gene on chromosome 22 (g.43989144G>A, GA genotype has the highest breeding value for PM), and the IL17RD gene on chromosome 22 (g.43990890G>A, GA genotype has the highest breeding value for PM). The five significantly associated SNP molecular markers mentioned above can be directly applied to marker-assisted selection (MAS) breeding of Chinese Holstein cattle for the peak daily milk yield trait. This marks a significant shift from traditional phenotype- or pedigree-based breeding models to a precise and efficient genotype-based breeding model. Directly detecting the genotypes of these key loci for selection and mating significantly overcomes the bottlenecks of traditional breeding methods (such as those relying on progeny testing), which suffer from long cycles, high costs, and limited accuracy. This invention greatly improves the accuracy and efficiency of selection for the complex trait of peak daily milk yield. Early selection using the molecular markers provided by this invention can effectively shorten generation intervals, accelerate the genetic improvement process of high-yielding Chinese Holstein cattle core breeding populations and superior breed groups, and achieve rapid accumulation of genetic gains. In actual breeding operations, genotyping detection of these five SNP loci can directly guide the precise selection and scientific mating of breeding bulls and cows, optimize the overall breeding program, and maximize the combination and transmission efficiency of favorable genotypes. By applying this invention for marker-assisted breeding, the average peak daily milk yield and potential 305-day milk yield of cattle herds can be significantly increased, providing strong scientific and technological support for dairy farming enterprises to reduce unit production costs, increase milk production and economic benefits, and contribute to the high-quality development of the dairy industry. Attached Figure Description

[0030] Figure 1 This is a Manhattan plot of the genome-wide association analysis of peak daily milk yield (PM) in Chinese Holstein cattle in this invention. Explanation of the figure labels: The markers above the dotted line represent the 32 peak daily milk yield SNPs screened in this invention, distributed on chromosomes 3, 5, 6, 11, 21, 22, 23, 25, 26, and 29 of dairy cattle.

[0031] Figure 2 This is a qq graph of genome-wide association analysis of peak daily milk yield trait in Chinese Holstein cattle in this invention.

[0032] Figure 3 This is a box plot showing the distribution of peak daily milk yield breeding values ​​of different genotypes at the SNP6_113000819 locus in Chinese Holstein cattle in this invention.

[0033] Figure 4 This is a box plot showing the distribution of peak daily milk yield breeding values ​​of different genotypes at the SNP11_87592639 locus in Chinese Holstein cattle in this invention.

[0034] Figure 5 This is a box plot showing the distribution of peak daily milk yield breeding values ​​of different genotypes at the SNP22_43988976 locus in Chinese Holstein cattle in this invention.

[0035] Figure 6 This is a box plot showing the distribution of peak daily milk yield breeding values ​​of different genotypes at the SNP22_43989144 locus in Chinese Holstein cattle in this invention.

[0036] Figure 7 This is a box plot showing the distribution of peak daily milk yield breeding values ​​of different genotypes at the SNP22_43990890 locus in Chinese Holstein cattle in this invention.

[0037] "*" indicates that the p-value shows a significant difference between the two genotypes; "****" indicates that the p-value shows a highly significant difference between the two genotypes. Detailed Implementation

[0038] The specific implementation of the invention will be further described below with reference to the accompanying drawings.

[0039] Example 1: Screening of SNP loci associated with peak daily milk yield in dairy cows

[0040] (I) Sample collection and DNA preparation: 380 Holstein cows were selected, and DNA was prepared for each individual using the Tiangen Blood Genomic DNA Extraction Kit.

[0041] (II) Phenotypic Collection and Breeding Value Estimation: 1038 lactation records and somatic cell scores were collected from 380 Holstein dairy cows, covering the period from 2015 to 2023. Single-trait animal models were used to estimate the breeding value (EBV) for each trait, and the dEBV for each trait was calculated using pedigree information.

[0042] The model is as follows: y = Xb + Z1α + Z2p + e,

[0043] Where y is the phenotypic value, X is the fixed effects matrix, b is the fixed effects variable such as farm year and season (HYS), calving year (CY), calving season (CS) or parity; Z1 is the animal individual additive effects matrix; Z2 is the animal permanent environmental effects matrix; e is the residual effect; α is the animal individual additive effect, and p is the permanent environmental effect.

[0044] The collected phenotypic data of 380 Chinese Holstein cattle from 2015 to 2023 were statistically analyzed using SPSS20 software. The peak daily milk yield (PM) trait of the herd is shown in Table 1.

[0045] Table 1. Statistical analysis of peak daily milk yield traits in Chinese Holstein cattle populations.

[0046]

[0047] The table above shows that the average PM value is 45.02 kg (standard deviation 14.33 kg), with moderate heritability (0.20).

[0048] (III) SNP genotyping: Whole-genome resequencing was used to sequence 380 individuals, followed by SNP genotyping using GATK 4.2 software, and then genotyping was performed using Beagle 5.4 software. Population SNP filtering was conducted using PLINK software. The filtering criteria were as follows: individual call rate of ≥97%; SNP detection rate of ≥95%; minimum allele frequency (MAF) greater than 0.05; and Hardy-Wenger-Bohr equilibrium test p-value less than 10. -6 Finally, 380 individuals and 1,030,098 SNPs were used for subsequent analysis.

[0049] (iv) Genome-wide association analysis: GWAS analysis of somatic scoring traits was performed using the FarmCPU method in rMVP software. The kinship matrix and four principal components were used as covariates. Boferroni was used to correct the p-values ​​of the GWAS analysis. The threshold for GWAS signal selection was 0.05 / N, where N equals 1030098.

[0050] The results are as follows Figures 1-2As shown, the Manhattan plot represents the genetic marker effect value, i.e., the genome-wide P-value after F-test, ordered by the physical location on the chromosome. The horizontal axis represents the physical location on the chromosome, and the vertical axis represents -log10P. The smaller the P-value, the stronger the association, indicated by a larger vertical axis. The horizontal dashed line in the Manhattan plot represents the significance level; when -log10(P) > 5, the SNP is considered significantly associated with the trait. The qq plot (Quantile-Quantile plot) shows the distribution of the actual P-value and the expected P-value without association null hypothesis. It is used to detect the influence of population stratification and individual kinship on association analysis. If the observed P-value and the expected P-value appear only at the rightmost end of the distribution, it indicates that the trait is not caused by population stratification. The QQ plot is mainly used to estimate the difference between observed and predicted values ​​of quantitative traits. Generally, the quantitative trait data we obtain are normally distributed. In GWAS studies, the X and Y axes of the QQ plot mainly represent the -lgP values ​​of each SNP. The predicted line is a dashed line at a 45° angle emanating from the origin.

[0051] Depend on Figure 1 Thirty-two significant GWAS signals associated with peak daily milk yield (PM) were identified, distributed on chromosomes 3, 5, 6, 11, 21, 22, 23, 25, 26, and 29 of dairy cows. The QQ plot further confirmed the reliability of the analysis results. Figure 2 ).

[0052] Table 2 further presents detailed information on these significant SNP sites. It can be seen that five SNP sites are located within the gene, indicating that these SNP sites are more related to gene function and will be the focus of subsequent analysis.

[0053] Table 2 shows the information of the 32 selected molecular markers.

[0054]

[0055]

[0056] Next, we used one-way ANOVA to examine the differences in peak daily milk yield breeding values ​​among different genotypes of these 5 SNP loci in Chinese Holstein cattle populations. We also used t-tests to compare the peak daily milk yield breeding values ​​between different genotypes, and box plots to visually display the distribution of peak daily milk yield breeding values ​​among individuals of different genotypes. Figure 3 , 4 (5, 6, 7); Cows with high peak daily milk yield breeding values ​​usually have higher milk production, indicating that the total milk production during lactation will be greater. They can be used as molecular markers to identify peak daily milk yield in Chinese Holstein cattle and applied to production.

[0057] like Figure 3 As shown in the box plot, the distribution of the three genotypes (GG, AG, AA) of the SNP locus 6_113000819_G_A in the peak daily milk yield breeding values ​​of Chinese Holstein cattle is shown. It can be seen that the AG genotype of dairy cattle at the SNP locus has a high peak daily milk yield breeding value, indicating that the AG genotype can be used as a marker for breeding dairy cattle to improve peak daily milk yield.

[0058] As shown in Table 3, all three genotypes of SNP locus 6_113000819_G_A significantly affected the peak daily milk yield breeding value of Chinese Holstein cattle (one-way ANOVA: P value < 0.05 was considered statistically significant; pairwise t-tests: P value < 0.05 was considered statistically significant). Specifically, the peak daily milk yield breeding value of AG genotype Chinese Holstein cattle was significantly higher than that of AA genotype Chinese Holstein cattle (P < 0.05).

[0059] Table 3 Molecular marker SNP6_113000819_G _ Comparative analysis of peak daily milk yield traits between A and Chinese Holstein cattle

[0060]

[0061]

[0062] like Figure 4 As shown, the box plot illustrates the SNP site 11_87592639_G _ The distribution of the three genotypes of A (GA, AA, GG) in the peak daily milk yield breeding values ​​of Chinese Holstein cattle; it can be seen that dairy cows with the GA genotype at the SNP locus have a high peak daily milk yield breeding value, indicating that the GA genotype can be used as a marker for breeding dairy cows to improve peak daily milk yield.

[0063] As shown in Table 4, the SNP site is SNP11_87592639_G. _ All three genotypes of A significantly affected the peak daily milk yield breeding value of Chinese Holstein cattle (one-way ANOVA: P-value < 0.05 was considered statistically significant; pairwise t-tests: P-value < 0.05 was considered statistically significant). Specifically, the peak daily milk yield breeding value of GA-type Chinese Holstein cattle was significantly higher than that of GG-type Chinese Holstein cattle (P < 0.05).

[0064] Table 4 Molecular marker SNP11_87592639G _ Comparative analysis of peak daily milk yield traits between A and Chinese Holstein cattle

[0065]

[0066] like Figure 5 As shown in the box plot, the SNP locus is SNP22_43988976G. _ The distribution of the three genotypes of A (AA, GA, GG) in the peak daily milk yield breeding values ​​of Chinese Holstein cattle; it can be seen that dairy cows with the GA and / or GG genotypes at the SNP locus have the highest peak daily milk yield, indicating that the GA and / or GG genotypes can be used as markers for breeding dairy cows to improve peak daily milk yield.

[0067] As shown in the table below, the SNP locus is SNP22_43988976G. _ All three genotypes of type A significantly affected the peak daily milk yield breeding value of Chinese Holstein cattle (one-way ANOVA: P-value < 0.05 was considered statistically significant; pairwise t-tests: P-value < 0.05 was considered statistically significant). Specifically, the peak daily milk yield breeding value of GA and / or GG type Chinese Holstein cattle was significantly higher than that of AA type Chinese Holstein cattle (P < 0.05).

[0068] Table 5 Molecular marker SNP22_43988976G _ Comparative analysis of peak daily milk yield traits between A and Chinese Holstein cattle

[0069] genotype mean ± standard deviation Pairwise comparison T-test (P) ANOVA(P) GG -0.431±0.156 GG / AA 0.029 0.0142 GA 0.376±0.596 GG / GA 0.1 AA -2.043±1.100 AA / GA 0.0046

[0070] like Figure 6 As shown in the box plot, the distribution of the three genotypes (GA, AA, GG) of the SNP locus SNP22_43989144G_A in the peak daily milk yield breeding values ​​of Chinese Holstein cattle is shown. It can be seen that dairy cows with the GA and / or GG genotypes at the SNP locus have higher peak daily milk yield breeding values, indicating that the GA and / or GG genotypes can be used as markers for breeding dairy cows to improve peak daily milk yield.

[0071] As shown in Table 6, all three genotypes of the SNP locus SNP22_43989144G_A significantly affected the peak daily milk yield breeding value of Chinese Holstein cattle (one-way ANOVA: P-value < 0.05 was considered statistically significant; pairwise t-tests: P-value < 0.05 was considered statistically significant). Specifically, the peak daily milk yield breeding value of GA and / or GG genotype Chinese Holstein cattle was significantly higher than that of AA genotype Chinese Holstein cattle (P < 0.05).

[0072] Table 6. Comparative analysis of the molecular marker SNP22_43989144G_A and the peak daily milk yield trait in Chinese Holstein cattle.

[0073] genotype mean ± standard deviation Pairwise comparison T-test (P) ANOVA(P) GG -0.435±0.156 GG / AA 0.0017 0.00719 GA 0.421±0.572 GG / GA 0.064 AA -2.533±1.190 AA / GA 6e-05

[0074] like Figure 7 As shown in the box plot, the distribution of the three genotypes (GA, AA, GG) of the SNP locus SNP22_43990890G_A in the peak daily milk yield breeding values ​​of Chinese Holstein cattle is shown. It can be seen that dairy cows with the GA and / or GG genotypes at the SNP locus have higher peak daily milk yield breeding values, indicating that the GA and / or GG types can be used as markers for breeding dairy cows to improve peak daily milk yield.

[0075] As shown in Table 7, all three genotypes of the SNP locus SNP22_43990890G_A significantly affected the peak daily milk yield breeding value of Chinese Holstein cattle (one-way ANOVA: P-value < 0.05 was considered statistically significant; pairwise t-tests: P-value < 0.05 was considered statistically significant). Specifically, the peak daily milk yield breeding value of GA and / or GG genotype Chinese Holstein cattle was significantly higher than that of AA genotype Chinese Holstein cattle (P < 0.05).

[0076] Table 7 Comparative analysis of the molecular marker SNP22_43990890G_A and the peak daily milk yield trait in Chinese Holstein cattle.

[0077] genotype mean ± standard deviation Pairwise comparison T-test (P) ANOVA(P) GG -0.435±0.156 GG / AA 0.0017 0.00719 GA 0.421±0.572 GG / GA 0.064 AA -2.533±1.190 AA / GA 6e-05

[0078] Example 2

[0079] This study investigated the application of primer sets targeting the five SNP marker sites in detecting peak daily milk yield traits in Chinese Holstein cattle.

[0080] The method described in this application for breeding / assisted breeding of Chinese Holstein breeds or strains associated with the peak daily milk yield trait in Chinese Holstein cattle can be applied. The method is as follows:

[0081] Genomic DNA was extracted from Chinese Holstein cattle, and the deoxyribonucleotide at locus 113000819 on chromosome 6 was detected. The result showed that the deoxyribonucleotide at locus 113000819 was either G or A, thus determining the genotype of the Chinese Holstein cattle to be tested as GG, AG, or AA. Based on breeding requirements, Chinese Holstein cattle with the GG, AG, or AA genotype were selected for further selection and / or breeding. The peak daily milk yield of AG genotype dairy cows is significantly higher than that of AA genotype dairy cows.

[0082] Genomic DNA was extracted from Chinese Holstein cattle, and the deoxyribonucleotide at locus 87592639 on chromosome 11 was detected. The result showed that the deoxyribonucleotide at locus 87592639 was either G or A, determining the genotype of the Chinese Holstein cattle to be tested as GA, AA, or GG. Based on breeding requirements, Chinese Holstein cattle with the GA, AA, or GG genotype were selected for further selection and / or breeding. The peak daily milk yield of GA-type dairy cows is significantly higher than that of GG-type dairy cows.

[0083] Genomic DNA was extracted from Chinese Holstein cattle, and the deoxyribonucleotide at locus 43988976 on chromosome 22 was detected. The result showed that the deoxyribonucleotide at locus 43988976 was either G or A, determining the genotype of the Chinese Holstein cattle to be tested as GA, AA, or GG. Based on breeding requirements, Chinese Holstein cattle with the GA, AA, or GG genotype were selected for further selection and / or breeding. The peak daily milk yield of GA and / or GG genotype dairy cows is significantly higher than that of AA genotype dairy cows.

[0084] Genomic DNA was extracted from Chinese Holstein cattle, and the deoxyribonucleotide at locus 43989144 on chromosome 22 was detected. The result showed that the deoxyribonucleotide at locus 43989144 was either G or A, thus determining the genotype of the Chinese Holstein cattle to be tested as GA, AA, or GG. Based on breeding requirements, Chinese Holstein cattle with the GA, AA, or GG genotype were selected and / or bred for further selection and / or breeding. The peak daily milk yield of GA and / or GG genotype dairy cows is significantly higher than that of AA genotype dairy cows.

[0085] Genomic DNA was extracted from Chinese Holstein cattle, and nucleotide 43,990,890 of chromosome 22 was detected. The sequence of nucleotide 43,990,890 was either G or A, determining the genotype of the cattle to be tested to be GA, AA, or GG. According to breeding requirements, Chinese Holstein cattle with GA, AA, or GG genotypes were selected and / or bred for further breeding. The peak daily milk yield of GA and / or GG genotype cattle is higher than that of AA genotype cattle.

[0086] Example 3

[0087] A SNP genotyping kit comprises specific primer pairs and / or probes for amplifying or detecting the five SNP sites described in Example 1, wherein the amplified region covers the 51st SNP site in the sequences shown in SEQ ID NO: 1-5. Those skilled in the art can readily design primers for amplifying the molecular marker or probes for identifying the molecular marker based on the molecular genetic markers of the present invention, thereby enabling the detection of the genetic marker. For example, the molecular genetic marker can be obtained by PCR amplification, followed by cloning and sequencing to obtain the corresponding sequence, or detected by Bsm-RFLP polymorphism.

[0088] The above description is a detailed description of the preferred embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical spirit of the present invention should fall within the patent scope covered by the present invention.

Claims

1. A SNP molecular marker associated with peak daily milk yield in dairy cows, characterized by: The SNP molecular markers associated with the peak daily milk yield trait in dairy cows include at least one of the following markers: Marker 1: Located at 113000819 bp on chromosome 6 of the bovine genome ARS-UCD2.0 version, the base at this site is G or A, corresponding to the 51st nucleic acid site in SEQ ID NO.1 of the nucleic acid sequence listing; Marker 2: Located at 87592639 bp on chromosome 11 of the bovine genome ARS-UCD2.0, the base at this site is G or A, corresponding to the 51st nucleotide site in SEQ ID NO.2 of the nucleic acid sequence listing; Marker 3: Located at 43,988,976 bp on chromosome 22 of the bovine genome ARS-UCD2.0, the base at this site is G or A, corresponding to the 51st nucleotide site in SEQ ID NO.3 of the nucleic acid sequence listing; Marker 4: Located at 43989144 bp on chromosome 22 of the bovine genome ARS-UCD2.0, the base at this site is G or A, corresponding to the 51st nucleotide site in SEQ ID NO.4 of the nucleic acid sequence listing; Marker 5: Located at 43990890 bp on chromosome 22 of the cow genome ARS-UCD2.0, the base at this site is G or A, corresponding to the 51st nucleic acid site in SEQ ID NO.5 of the nucleic acid sequence listing.

2. The use of the SNP molecular marker as described in claim 1 in the selection or assisted selection of dairy cow breeds or strains with peak daily milk yield traits, specifically for the selection or assisted selection of dairy cows with high / low peak daily milk yield.

3. A method for breeding or assisted breeding of dairy cow breeds or strains related to peak daily milk yield using the SNP molecular markers described in claim 1, characterized in that: The specific steps are as follows: Genomic DNA was extracted from dairy cows, and nucleotide sequence at position 113000819 of chromosome 6 was detected. If the sequence at position 113000819 was G or A, the genotype of the dairy cow to be tested was determined to be AG, AA, or GG. AG-type cows were selected for further selection and / or breeding as needed. The peak daily milk yield of AG-type cows was higher than that of AA-type cows. Genomic DNA was extracted from dairy cows, and nucleotide 87592639 of chromosome 11 was detected. If the sequence of nucleotide 87592639 was G or A, the genotype of the dairy cow to be tested was determined to be GA, AA, or GG. Dairy cows with the GA genotype were selected for further selection and / or breeding as needed. The peak daily milk yield of the GA genotype dairy cows was higher than that of the AA genotype dairy cows. Genomic DNA was extracted from dairy cows, and nucleotide 43,988,976 of chromosome 22 was analyzed. If the sequence of nucleotide 43,988,976 was G or A, the genotype of the dairy cow was determined to be GA, AA, or GG. GA-type cows were selected for further selection and / or breeding as needed. The peak daily milk yield of GA and / or GG-type cows was higher than that of AA-type cows. Genomic DNA was extracted from dairy cows, and nucleotide 43,989,144 of chromosome 22 was analyzed. If the sequence of nucleotide 43,989,144 was found to be G or A, the genotype of the dairy cow to be tested was determined to be GA, AA, or GG. GA-type cows were selected for further selection and / or breeding as needed. The peak daily milk yield of GA and / or GG-type cows was higher than that of AA-type cows. Genomic DNA was extracted from dairy cows, and nucleotide 43,990,890 of chromosome 22 was detected. If the sequence of nucleotide 43,990,890 was G or A, the genotype of the dairy cow to be tested was determined to be GA, AA, or GG. Dairy cows with the GA genotype were selected for further selection and / or breeding as needed. The peak daily milk yield of the GA and / or GG genotype dairy cows was higher than that of the AA genotype dairy cows.

4. The method according to claim 3, characterized in that, The genotype GG or AA in the cow's chromosome 6 represents a homozygous individual with nucleotide G at position 113000819 or a homozygous individual with nucleotide A. The genotype GG or AA in the 11th chromosome of the dairy cow represents a homozygous individual with nucleotide G at position 87592639 or a homozygous individual with nucleotide A at position 87592639, respectively. The genotype GG or AA in the 22nd chromosome of the dairy cow represents a homozygous individual with nucleotide G at position 43988976 or a homozygous individual with nucleotide A at position 43988976, respectively. The genotype GG or AA in the 22nd chromosome of the dairy cow represents a homozygous individual with nucleotide G at position 43989144 or a homozygous individual with nucleotide A. The genotype GG or AA on chromosome 22 of the dairy cow indicates a homozygous individual with nucleotide G at position 43990890 or a homozygous individual with nucleotide A at position 43990890, respectively.

5. An SNP genotyping detection kit, characterized in that, It contains specific primer pairs and / or probes for amplifying or detecting the five SNP sites of claim 1, wherein the amplification region covers the 51st SNP site in the sequence shown in SEQ ID NO:1-5.

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