Genetic Effects Of The HPA Axis Key Genes On Lactation Traits Of Xinjiang Brown Cattle

In the present research, the genetic polymorphisms of GH gene, PRL gene,PROP1gene, POU1F1gene, HESX1gene, LHX3gene and LHX4gene of theXinjiang Brown cattles were detected by polymerase chain reaction-singlestrand conformation polymorphism (PCR-SSCP) and the relationship betweengenotypes and average daily milk yield, Milk composition and SCS, at DNAlevel theoretical basis for the improved development and utilization of XinjiangBrown cattle. Simultaneously, and polymerization effect method was used toAnalyzed Genetic pyramiding effect The PRL-exon4and POU1F1-exon3,GH-intron3and LHX3-exon6, GH-exon5and PROP1-exon1gene. The testanalysis results in the following:(1) GH gene: The GH-intron3and GH-exon5Respectively have AA, AB, BBand CC, CD, DD，and predominant allele A and C; Different genotypes of GHgene intron3had Highly significant effect on milk performance, Milk fat, Rateof lactose (P<0.01), significant effect on Milk protein percentage(P<0.05), hadno significant effect on Total solids and SCS(P>0.05); Different genotypes ofGH gene exon5had significant effect on milk performance(P<0.05), had nosignificant effect on Milk protein percentage, Milk fat, Rate of lactose, Totalsolids and SCS(P>0.05).(2) PRL gene: The results showed that two new mutation (G8377C, A8398G)and Leading to amino acid changes in exon4of PRL gene were found in three genotypes named EE， EF and LL in Xinjiang Brown Cattles. Genotypefrequencies were0.345,0.526and0.129for EE，EF and FF, respect ively.Allelefrequencies were0.608,0.392for E and F. The results of the least squaresanalysis showed FF and EF cows are of higher milk protein percentage than EEindividuals(P<0.05), and EE cows are of higher daily milk yield than EFindividuals(P<0.05). These results suggest that mutations in exon4of PRL genemay be an important locus for milk performance of Xinjiang Brown cattles.(3) PROP1gene: No polymorphisms for exon2of PROP1gene and exon3ofPROP1gene loci were detected. Exon1of PROP1gene were found in threegenotypes named GG，GA and AA in Xinjiang Brown Cattles. Allele frequencieswere0.686,0.314for G and A. DNA sequence analysis revealed that the onemutations occurred in321G→A, and were all silent mutations. And GG cowsare of higher milk protein percentage than GA individuals(P<0.05).(4) POU1F1gene: exon3of POU1F1gene loci found two Allele frequencieswhich belongs to the moderate polymorphism (0.5>PIC>0.25). exon3ofPOU1F1gene loci LL cows are of higher milk protein percentage than TLindividuals(P<0.01), TT cows are of higher Rate of lactose than TLindividuals(P<0.01), LL cows are of Total solids than TT individuals(P<0.05).(5) LHX3gene: exon6of LHX3gene Allele frequencies were0.542,0.458for Mand N. exon3of LHX3gene loci MN cows are of higher milk performance thanNN individuals(P<0.01), NN cows are of higher milk protein percentage thanNN individuals(P<0.01). (6) LHX4gene and HESX1gene：No polymorphisms for LHX4gene and HESX1gene loci were detected.(7)1PRL and POU1F1Combined gene pyramiding effect： gene loci FF-LLCombined genotypes cows are of higher Daily milk yield, milk fat, milk proteinpercentage, lactose and total solids than other Combined genotypes.2GH geneintron3and LHX3gene exon6gene pyramiding effect： gene loci CC-MNCombined genotypes cows are of higher Daily milk yield, lactose than otherCombined genotypes, gene loci DD-NN Combined genotypes cows are of highermilk fat, milk protein percentage, total solids than other Combined genotypes,gene loci DD-NN Combined genotypes cows are of lower SCS than otherCombined genotypes.3GH gene exon5and PROP1-exon1gene pyramidingeffect： gene loci AB-AA Combined genotypes cows are of higher Daily milkyield, lactose than other Combined genotypes, gene loci BB-AA Combinedgenotypes cows are of higher milk fat than other Combined genotypes. gene lociBB-GG Combined genotypes cows are of higher milk protein percentage thanother Combined genotypes.