Association Analysis Between Genetic Polymorphism Of Lactoferrin Gene And Economic Traits In Xinong Saanen And Guanzhong Dairy Goat Breeds

In this thesis, 549 blood samples were collected in Xinong Saanen and Guanzhong dairy goat breeds respectively. The association analysis between the genetic variation of 17 exons of lactoferrin gene (lactoferrin gene) and body size traits (body height, body length, chest circumference) and milk yield and milk composition (milk protein, milk fat, lactose and total milk solids, non-fat solids, milk pH value) was carried out in two dairy goat breeds using PCR-SSCP, PCR-RFLP, DNA sequencing and bioinformatics techniques. The final aim is to obtain the molecular genetic markers which are associated with economic traits and provide the scientific basis for the molecular breeding of dairy goat. The important findings are as follows:1. Five SNPs were detected in P2, P4, P6, P10 loci among 17 exon loci (P1-P17) of lactoferrin gene in Xinong Saanen and Guanzhong dairy goat breeds. Three different genotypes with AA, GG and GA were detected for P2 locus. Two different genotypes with CT and TT were detected for P4 locus. Two SNPs with two different genotypes of TT and TG and AA and AG respectively were detected for P6 locus. Two different genotypes with TC and CC were detected for P10 locus of lactoferrin gene in Xinong Saanen and Guanzhong dairy goat breeds.Among the AA, GG and GA genotypes for P2 locus, the G/A allele frequencies for Xinong Saanen and Guanzhong breeds were 0.9552/0.0448 and 0.9448/0.0552, respectively. P2 locus indicated low polymorphism (PIC<0.25) and was in the Hardy-Weinberg equilibrium. The distribution of the genotypes of P2 locus between these two dairy goat breeds was not significant (P > 0.05).Among the TT and TC genotypes for P4 locus, the T/C allele frequencies for Xinong Saanen and Guanzhong breeds were 0.8806/0.1194 and 0.9075/0.0925, respectively. P4 locus indicated low polymorphism (PIC<0.25) and was in the Hardy-Weinberg equilibrium. The distribution of the genotypes of P4 locus between these two dairy goat breeds was not significant (P > 0.05).Among the two linkage genotypes TT, TG, and AA,AG for P6 locus, the T(A) and G(G) allele frequencies for Xinong Saanen and Guanzhong breeds were 0.9164/0.0836,0.9216/0.0784, respectively. P6 locus indicated low polymorphism (PIC<0.25) and was in the Hardy-Weinberg equilibrium. The distribution of the genotypes of P6 locus between these two dairy goat breeds was not significant (P > 0.05).Among the CC and TC genotypes for P10 locus, the T/C allele frequencies for Xinong Saanen and Guanzhong breeds were 0.8657/0.1343 and 0.8897/0.1103, respectively. P10 locus indicated low polymorphism (PIC<0.25) and was in the Hardy-Weinberg equilibrium. The distribution of the genotypes of P10 locus between these two dairy goat breeds was not significant (P > 0.05).2. Significant associations between the different genotypes of P2 and P4 loci of lactoferrin gene and economic traits were found in two dairy goat breeds.No association between different genotypes of P6 and P10 loci and body size and milk yield were found in two dairy goat breeds (P>0.05) using the SPSS (16.0) software and adopting the least square linear fitting method to analyze the mentioned five mutations. Moreover, no significant effects between different genotypes of P6 and P10 loci and milk fat, protein, dry matter, non-fat solids, lactose content and milk density were found in two dairy goat breeds (P>0.05).In the GG, GA and AA genotypes of P2 locus, the individuals with AA genotype had larger body height than those with GG genotype (P <0.05). While, the individuals with AA genotype had higher milk protein percentage and pH value than those with AG and GG genotype (P <0.05) among six indicators including milk fat, protein, dry matter, non-fat solids, lactose content and pH value in two dairy goat breeds. However, no effects between different genotypes of P2 locus and other remaining four indicators were detected (P>0.05).In the TT and TC genotypes of P4 locus, the individuals with TC genotype had extremely higher milk fat than those with TT genotype (P<0.001), and the individuals with TC genotype had higher dry matter and pH value than those with TT genotype (P<0.05).In conclusion, P2 and P4 locus of LF gene can be preliminarily considered as a candidate gene for economic traits breeding in dairy goat.