The gene encoding regulatory subunit 15 A of protein phosphatase 1 produces a protein that is a universally present protein phosphatase in eukaryotic cells.In this study,genomic DNAs were extracted from the blood of 89 Chinese Holstein cows and were used as templates for PCR amplification of the target fragment of the PPP1R15A gene.The product was tested and a polymor-phic site,E3-250T＞A was found.The polymorphism of this side and its correlation with milk pro-duction traits in Chinese Holstein cattle were statistically analyzed using SPSS 23.0 software.The findings revealed three genotypes at this site:AA,AT and TT.Cows possessing the AT and TT genotypes exhibited significant differences(P＜0.01)in milk fat and solid non-fat content com-pared to those with the AA genotype.While no significant differences were noted for other milk production traits,including milk yield,protein,lactose,somatic cell count,blood urea nitrogen,and corrected milk.The identification of functional SNPs in the PPP1R15A gene provides a theoretical basis for further research and identification of causal variations in the cow PPP1R15A gene.

In order to reveal the association between single nucleotide-based polymorphism(low density lipoprotein receptor-related protein 5,LRP5),DNA of 98 Chinese Holstein cows were ex-tracted and the LRP 5 gene polymorphism locus was detected by direct sequencing,and related dif-ferent genotypes and milk quality traits at the SNP loci was analyzed.The results showed that three SNPs were found on the fourth intron of the LRP 5 gene,I4-90 C＞T,I4-229 C＞A and I4-570 A＞G.Among them,I4-90 C＞T had TT,CC and TC genotypes,and TC genotype was signifi-cantly higher than TT and CC genotypes(P＜0.05).However,mutations at this locus were not significantly associated with milk yield and fat content(P＞0.05);genotypes CC and C for I4-229 C＞A;genotypes AA,GG and GA for I4-570 A＞G.The two mutation sites showed no significant correlation with milk quality traits in Chinese Holstein dairy cows(P＞0.05).The above results indicate that the I4-90 C＞T site of LRP 5 gene can be used for marker-assisted selection as molec-ular markers affecting milk quality traits in Chinese Holstein cows.

This study aims to investigate the relationship between single nucleotide polymorphisms(SNPs)in the 3'-phosphoadenosine 5'-phosphosulfate synthase 2(PAPSS2)gene and milk quality traits in Chinese Holstein cows.A total of 141 Chinese Holstein cows were sampled,and their DNA was extracted to detect polymorphic sites in the PAPSS2 gene using direct sequencing technology.The genotypes at different SNP sites were then correlated with milk quality traits.The results i-dentified three SNP sites in the second intron of the PAPSS2 gene:I2-3686 A＞G,I2-3854 G＞C,and I2-3917 G＞A,each exhibiting three genotypes.Specifically,at the first SNP site,individuals with the AG genotype demonstrated significantly higher milk fat and solids content compared to those with the GG genotype(P＜0.05).At the second SNP site,individuals with the GG genotype exhibited significantly higher urinary nitrogen content than those with the GC and CC genotypes(P＜0.05).No significant differences were observed in milk quality traits associated with the third SNP site.These findings suggest that SNP sites in the PAPSS2 gene can serve as molecular mark-ers influencing milk quality traits in Chinese Holstein cows,providing potential applications for marker-assisted selection in dairy cattle.

In order to reveal the association between single nucleotide-based polymorphism(low density lipoprotein receptor-related protein 5,LRP5),DNA of 98 Chinese Holstein cows were ex-tracted and the LRP 5 gene polymorphism locus was detected by direct sequencing,and related dif-ferent genotypes and milk quality traits at the SNP loci was analyzed.The results showed that three SNPs were found on the fourth intron of the LRP 5 gene,I4-90 C＞T,I4-229 C＞A and I4-570 A＞G.Among them,I4-90 C＞T had TT,CC and TC genotypes,and TC genotype was signifi-cantly higher than TT and CC genotypes(P＜0.05).However,mutations at this locus were not significantly associated with milk yield and fat content(P＞0.05);genotypes CC and C for I4-229 C＞A;genotypes AA,GG and GA for I4-570 A＞G.The two mutation sites showed no significant correlation with milk quality traits in Chinese Holstein dairy cows(P＞0.05).The above results indicate that the I4-90 C＞T site of LRP 5 gene can be used for marker-assisted selection as molec-ular markers affecting milk quality traits in Chinese Holstein cows.

This study aims to investigate the relationship between single nucleotide polymorphisms(SNPs)in the 3'-phosphoadenosine 5'-phosphosulfate synthase 2(PAPSS2)gene and milk quality traits in Chinese Holstein cows.A total of 141 Chinese Holstein cows were sampled,and their DNA was extracted to detect polymorphic sites in the PAPSS2 gene using direct sequencing technology.The genotypes at different SNP sites were then correlated with milk quality traits.The results i-dentified three SNP sites in the second intron of the PAPSS2 gene:I2-3686 A＞G,I2-3854 G＞C,and I2-3917 G＞A,each exhibiting three genotypes.Specifically,at the first SNP site,individuals with the AG genotype demonstrated significantly higher milk fat and solids content compared to those with the GG genotype(P＜0.05).At the second SNP site,individuals with the GG genotype exhibited significantly higher urinary nitrogen content than those with the GC and CC genotypes(P＜0.05).No significant differences were observed in milk quality traits associated with the third SNP site.These findings suggest that SNP sites in the PAPSS2 gene can serve as molecular mark-ers influencing milk quality traits in Chinese Holstein cows,providing potential applications for marker-assisted selection in dairy cattle.