| The intramuscular fat has become increasing popular as an important parameter in pigs breeding for its effects on meat quality.According to our previous result,here we constructed and improved B-ultrasound prediction model of intramuscular fat content of live Erhualian pigs.After verifying the accuracy of the model,it is used to select the individuals with high intramuscular fat content of Erhualian pig.Detection of polymorphisms in the upstream regulatory regions of KDR and PPARG genes by AS-PCR typing and DNA sequencing and correlation analysis was performed on individuals with different genotypes of the mutation site and intramuscular fat content.Using the method of in vivo prediction of intramuscular fat content of pigs and molecular assisted selection,the individuals with excellent intramuscular fat traits were selected and to promote the selection process.The main findings and results are as follows:1.The B-scan images of 64 purebred Erhualian pigs were taken for analysis.Adobe Photoshop CS6 software was used to extract the average gray valuev N2,eye muscle contour average gray value H,the brightest line of the third bright line average gray value L and backfat thickness F of the scanning area in the images.Calculate prediction parameters X3=H/L1×10.The model for predicting IMF was developed using linear regression analysis with IMF measured as dependent variables X2,F,H and body weight as independent variables.Another 30 erhualian pigs were selected to analyze the correlation between the predicted value of intramuscular fat content and the actual measured value to verify the accuracy of the model.The final improved model equation is as follows:Y=0.826X3+0.178E-0.096N2-0.371 The three parameters of X3,N2 and F reached significant levels(P<0.05),and the model determination coefficient R2=0.421.Pearson correlation coefficient between predict IMF content and actual content was 0.642(P<0.01),and spearman correlation coefficient was 0.594(P<0.01).It indicates that the model has high accuracy and can be used to predict the intramuscular fat content of Erhualian pigs.2.The AS-PCR and sequencing methods were used to genotype the KDR gene g.-1633 T>C SNP locus and PPARG gene g.-1633T>C SNP locus of 70 erhualian pig samples,and the correlation between genotype and intramusculus fat content was analyzed subsequently.The results showed that there were three genotypes at the g.-1633T>C site of KDR gene,and the intramusculus fat content of AA type individuals was significantly higher than the intramusculus fat content of AG type and GG type individuals(P<0.05).PPARG gene g.-1633T>C locus,the individuals with TT type intramuscular fat content was higher,but there was no significant difference between CT type and CC type(P>0.05).3.B-ultrasound scan images of the longissimus dors i muscle were collected from 1866-month old Erhualian pigs.The constructed predictive model was used to predict intramuscular fat content.At the same time the ear samples of above 186 pigs were collected and the DNA was extracted for genotyping,and the population of Erhualian pigs was predicted to have an average intramuscular fat value of 3.5393%±1507%;AS-PCR typing and population genetic analysis showed that the KDR gene g.-1318A>G locus polymorphism information content PIC=0.3747 in the tested population,was moderate polymorphism,and it was in Hardy-Weinberg genetic balance(P>0.05);The polymorphism information content of PPARG gene was PIC=0.3747,which was moderate polymorphism,which deviated from Hardy-Weinberg genetic balance(P<0.05).4.According to the intramuscular fat predicted value combined with the KDR gene upstream regulatory region polymorphism,35 individuals with excellent intramuscular fat content trait were selected from 186 6-month-old Erhualian pigs,including 28 sows and 7 boars.Our study provides reference for further breeding works on the Erhualian pigs. |
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