The Association Of Polymorphisms Of ACACA Gene And SCD Gene With Milk Traits In Laoshan Dairy Goat

The breeding improvement of milk production traits is limited by conventional breeding technology in LaoShan Dairy Goat, because the heritability of milk production traits is very low. So it is very important to find the mayor genetic markers related to milk production traits. The aim of present study was to research genetic polymorphism of promoter III in ACACA gene and the flanking sequence and Exon3 in SCD gene, and the association of polymorphism with milk traits in Laoshan dairy goat, so we can provide the basic information for breeding and selection of LaoShan Dairy Goat. By combining denaturing high- performance liquid chromatography(PCR-DHPLC) with direct sequencing, SNPs in promoter III of ACACA gene were identified, and identifying SNPs in flanking sequence and Exon3 of SCD gene by direct sequencing in Laoshan dairy goat population containing174 individuals. Least square method was performed to evaluate the association of polymorphisms with milk traits in Laoshan dairy goat;? Genetic diversities of all mutation sites were analyzed by Popgen3.2 program; Correlation coefficient of body measurement and body weight with milk traits, and the association of polymorphisms with milk traits were evaluated through SAS9.2 program. The results as follows:(1)Three SNPs have been identified, B/D at 1206bp, A/C at 1255bp, M/N at 1322bp in promoter III in ACACA gene. The distribution of alleles and genotypes in both Group F and Group P were not in balance, but still under Hardy-Weinberg equilibrium. Four SNPs have been identified, E315 E/e and E368H/h in Exon3, I346 R/r and I355Q/q in intron3 of SCD gene. The distribution of alleles and genotypes were all under Hardy-Weinberg equilibrium, and?the alleles and genotypes distribution of E315 were consistent with that of I355,?so the two sites were linkaged.(2)Body weight, body height, body length had negative correlation with all milk ingredients traits at significant (P<0.05) or highly significant level(P< 0.01). The correlation between body length and milk yield at 300 days was positive at significant level (P<0.05), and correlations were positive that of body weight and circumference with milk yield at highly significant level(P< 0.01) .(3)The differences among different genotypes of ACACA gene were not significant in the whole population, only the difference between different herbs exists. Further, the differences between different genotypes were analyzed in Group F and Group P respectively. The 1206 site in F group, allele B had a positive effect on protein rate, lactose rate and non-fat rate, and the difference between genotypes BB and BD was significant for protein rate and fat rate (P<0.01), for non-fat and milk density (P<0.05). The substitution effects for protein rate, lactose rate and non-fat were significant (P<0.05). While in P group, the differences between genotypes BD and BB for all milk traits were not significant (P>0.05). Allele N was the dominant allele for lactose rate,while was the negative allele for milk yield at 1322 site in F group, and the difference between genotypes MN and MM was significant for milk yield (P< 0.01) and for lactose rate(P<0.05). The substitution effects for lactose rate and milk yield were 0.12% and -52.22kg (P<0.01) respectively. In P group, allele M was the dominant allele for protein rate, lactose rate, non-fat and milk density, the difference between genotypes MM and MN was significant for protein rate, lactose rate, non-fat and milk density (P<0.05). The substitution effects for lactose rate and non-fat were -0.25%, -0.44%(P<0.05) respectively.(4)The difference between genotypes EE/QQ and ee/qq was significant for all milk ingredients at significant(P<0.05) or highly significant level(P<0.01), and the difference between genotypes EE/QQ and Ee/Qq was significant for protein rate, milk density(P<0.05). Allele E/Q had positive effects on all milk ingredients, and the additive effects were highly significant (P<0.01), while the domance effects were not significant (P>0.05). The difference between genotype hh with genotypes HH and Hh was significant for all milk ingredients at significant (P<0.05) or highly significant level (P<0.01), and allele h had positive effects on all milk ingredients. Additive effects and domance effects both were highly significant (P<0.01). Milk yield at 300 days of genotype rr was higher than RR at highly significant level (P<0.01), allele r had positive effect on milk yield at 300 days, but it had no significant effect on milk ingredients (P>0.05). Analyzing the association of polymorphisms in SCD gene with milk traits in Group F and Group P respectively. The difference among genotypes were very low in Group F, while that was higher in Group P, which shows that effects of SCD gene on milk traits mainly owing to effects in Group P of Laoshan dairy goats.