Effects Of Different Hormone Combinations And Estrus Related Gene Polymorphism On Estrus In Dairy Sheep

In order to further improve the estrus rate of dairy sheep,find out the best hormone combination for estrus synchronization treatment and molecular markers affecting the estrus phenotype of dairy sheep.In this experiment,three hormone combinations[group A:Controlled Intemal Drug Release（CIDR）+Prostaglandin（PG）+Pregnant Mare Serum Gonadotropin（PMSG）,group B:CIDR+PG+Follicle stimulating hormone（FSH）,group C:CIDR+PG+Luteinizing Hormone Releasing Hormone A₃ for Injection（LHRH-A3）]were used to treat the estrus synchronization of Donghu hybrid dairy sheep.The estrus synchronization rate and conception rate were compared to explore the best estrus synchronization treatment method of Donghu hybrid dairy sheep;In addition,Kompetitive Allele-Specific PCR（KASP）technology was used to detect the genotyping of estrus-related genes in the Donghu hybrid dairy sheep population,and the general linear model was used to analyze the correlation between different genotypes and estrus identification scores.Find out the key loci affecting estrus trait,provide credible molecular markers for rapid breeding of estrus trait in dairy sheep.The results of this study are as follows:1、Comparative analysis of the effect of three hormone combinations on simultaneous estrus treatment of Donghu hybrid milk Sheep（1）The estrus rate and conception rate of group A were 85.37%and 77.14%,which were significantly higher than those of the other two groups.（2）In terms of reproductive hormones at different time points before and after estrus,FSH concentration in group A at 48h was significantly higher than that in the other two groups（P<0.05）;The concentration of luteinizing hormone（LH）in group A was significantly higher than that in group C at 48h of estrus（P<0.05）,but there was no significant difference between group A and group B（P>0.05）;The estradiol（E₂）concentration of group A was significantly lower than that of group C at 48h of estrus（P<0.05）,but had no significant difference with group B（P>0.05）;There was no significant difference in progesterone（P₄）concentration among the three groups at 48h of estrus（P>0.05）;The prolactin（PRL）concentration in group A was significantly higher than that in group B（P<0.05）and was extremely significantly higher than that in group C（P<0.01）at 48h of estrus.（3）Compared the content of total protein（TP）,alanine aminotransferase（ALT）,total cholesterol（TC）and alkaline phosphatase（AKP）in the three treatment groups at different time points,at 48h of estrus,there was a significant difference in TC content between group A and group C at 48h of estrus（P<0.01）,and there was a significant difference in AKP content（P<0.05）.There was no difference in TP and ALT content in serum among the three groups（P>0.05）.（4）At different time points,there was no difference in immunoglobulin A（lg A）,immunoglobulin G（lg G）and immunoglobulin M（lg M）of three groups（P>0.05）.2、Comparative analysis of reproductive hormones,biochemical indexes and immune indexes between estrus ewe and non-estrus ewes（1）At 48h of estrus,the concentration of FSH,LH and PRL in estrus ewes were higher than those in non-estrus ewes,but the difference was not significant（P>0.05）;From 24h to72h in estrus,E₂concentration in non-estrus sheep was higher than that in estrus（P>0.05）;The concentration of P₄ did not change significantly between estrus ewes and non-estrus ewes.（2）There was no significant difference in serum TP,ALT,TC and AKP levels on the day of releasing plug,the sixth day of releasing plug,the day of removing plug,24 hours of estrus,48 hours of estrus and 72 hours of estrus（P>0.05）.（3）In the comparison of immune indexes,the contents of Ig A,Ig G and Ig M in estrus ewes at 24h and 48h were higher than those in non-estrus ewes,but the difference was not significant（P>0.05）.3、Polymorphism detection of estrus related gene loci and correlation analysis with estrus identification score（1）3β-hydroxysteroid dehydrogenase 1（HSD3B1）gene g.101951669C>A,g.101942693G>A,Type II thyroid hormone deiodinase（DIO2）gene g.95881327G>C,g.95881318T>C.Kisspeptin-1（KISS1）gene g.1577229C>T,Melatonin receptor 1A（MTNR1A）gene g.17354971A>G,g.17355452C>T,g.17355458A>G and Steroidogenic acute regulatory protein（STAR）gene g.31959875A>C had three genotypes:wild homozygote,mutant heterozygote and mutant homozygote;Melatonin receptor 1B（MTNR1B）gene g.1684557T>G,Cholesterol side-chain cleavage enzyme（CYP11A1）gene g.32238524A>G and STAR gene g.31959747T>C,three sites only exist wild homozygous genotype and mutant heterozygous genotype.（2）The results of association analysis showed that the estrus identification scores of CC type and CT type at g.1577229 of KISS1 gene were significantly higher than TT,and the difference was significant（P<0.01）.There was significant difference between TT type and TC type at g.31959747 STAR gene（P<0.01）,and TT type was higher than TC type in estrus identification scores.There were no significant difference in estrus identification scores among different genotypes of other gene loci（P>0.05）.（3）The results of association analysis between pyramiding genotypes and estrus identification score showed that there were five pyramiding genotypes of TTAA,TTAC,TTCC,TCAA and TCAC in g.31959747 and g.31959875 of STAR gene,and the score of estrus identification of TCAC genotype was significantly lower than that of the other four genotypes（P<0.01）.In summary,through the comparison of reproductive performance,serum reproductive hormones,biochemical indexes,and immune indexes,it was found that the CIDR+PG+PMSG group had the best estrus synchronization effect.There are also difference in reproductive hormone secretion and immune indexes between estrus ewes and non-estrus ewes.In addition,the results of association analysis showed that the g.1577229 locus of KISS1 gene and the g.31959747 locus of STAR gene may be the key loci affecting the estrus phenotype of dairy sheep.This study explored the best treatment method for estrus synchronization of Donghu hybrid dairy sheep,and identified SNP loci related to estrus traits through association analysis,which provided a reference for molecular breeding of dairy sheep.