The Association Analysis Of Three Genes Such As DGAT1 On Milk Production Traits Of Holstein

The polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP) and polymerase chain reaction-single-strand conformation polymor-phism(PCR-SSCP) technique combining with sequencing technique were used during the investigation of polymorphism of DGAT1 gene, PRL gene, and κ-CN gene exon 4 and exon 5 in the population of Australian-Holstein-Friesian cows in reclamation area of Hei Longjiang. The correlation analysis between their polymorphism and daily milk production, butter-fat percentage, protein percentage, SCS, and other important indicators in DHI report. The pupose of this study is to provide a data reference for the genetic breeding and varietal improvement of the cattle in reclamation area of Hei Longjiang. The results are as follows:1. Genotype AA, AG and GG were detected at locus K232 A on DGAT1 gene. The allele frequency of A and G was 0.1574 and 0.8426 respectively. The locus had low polymorphism information contents. The result of chi-square test showed the locus was on hardy-weinberg equilibrium(P>0.05).The genotype AG had a certain influence on milk yield and protein percentage.2. Genotype AA, AG and GG were detected at locus 906, on PRL gene. The allele frequency of A and G was 0.5307 and 0.4693 respectively. The locus had intermediate polymorphism information contents. Result of chi-square test showed the locus was on hardy-weinberg disequilibrium(P<0.05). The result of association analysis showed that the polymorphism of PRL gene had an remarkable influence on milk yield and butter-fat percentage(P<0.05). The genotype GG of this locus had a significant correlation with high milk yield and low butter-fat percentage in the first lactation(P<0.05).3. Five mutation site were detectived on κ-CN gene exon 4, they are locus 13068, locus 13165, locus 13173 and locus 13124. Genotype AA, AC and CC were detected at locus 13104. The allele frequency of A and C was 0.8704 and 0.1296 respectively. The locus had low polymorphism information contents. Result of chi-square test showed the locus was on hardy-weinberg equilibrium(P>0.05). The genotype AC of this locus had a higher milk yield, higher total butter-fat.4. There were only two genotype detected at locus 15124 on κ-CN gene exon 5, they are genotype TT and TC. The allele frequency of T and C was 0.8938 and 0.1062 respectively. The locus also had a low polymorphism information contents as the locus in exon 4 of κ-casein gene. As well as the result of chi-square test showed the locus was on hardy-weinberg equilibrium(P>0.05). The genotype TT of this locus was a dominant genotype in the first and second lactation, when it comes to the third lactation, genotype TC became to be the dominant genotype.5. Haplotype ACTT of κ-CN gene was descoverd to have a significant correlation with high daily milk production, high peak milk production, high milk yield of 305 days, low butter-fat percentage and long calving interval.