Study On In Vivo Intramuscular Fat Pecentage Measuring Technique Using B-type Ultrasound In Erhualian Pigs

Intramuscular fat percentage(PIMF)is an important factor affecting the quality of pork,reducing backfat thickness while increasing intramuscular fat percentage is an effective way to improve meat quality.However,due to the intramuscular fat percentage can not direct measurement in living body,thereby restrict the effective selection for this trait.Therefore,it’s of a great significance to develop the techniques and methods for the determination of intramuscular fat percentage for selection of meat quality traits in Erhualian pigs.In this study,eight methods have been applied to explore the intramuscular fat percentage of determination techniques in Erhualian pigs in vivo,through established B-type ultrasound predicted model,body-scale data correlation analysis and molecular marker.The experiment selected 122 purebred Erhualian pigs,through the B-type ultrasound detector and measurements in vivo were made at the three sites of the thickest of the back(P1),thoracolumbar junction(P2)and lumbosacral joint(P3),and record the corresponding pig weight and body size standards.On this basis,the following work is carried out:(1)Obtaining the measuring backfat thickness through B-type ultrasound images,then correlation analysis between actual measuring backfat thickness and obtain the linear predictive model.Then analysing the images of 30 Erhualian pigs through eight methods,then featuring extraction in the images as the predicted parameters and different methods select different predicted parameters.Linear simulation between parameters after treatment(predicted parameters)and actual intramuscular fat percentage,finally obtaining the intramuscular fat percentage predicted model and correlation,according to the size of the correlation coefficients,choosing the optimal predicted method and model.Then verifying the optimal predicted method through seclecting 63 images of Erhualian pigs and evaluateing the accuracy of the predicted model according to the correlation after verification.(2)Through the analysis of correlation between body weight and body size of phenotypic data and backfat thickness and intramuscular fat percentage or other economic indicators,we can explore the phenotypic indicators that can be used for the prediction of backfat thickness and intramuscular fat percentage in living body,to estimate the backfat thickness and intramuscular fat percentage of Erhualian pigs.The result shows that it was feasible and accurate which predicting the backfat thickness and intramuscular fat pencentage in vivo by using this ultrasound.(3)KDR,as one of the major receptors of VEGF,is an important intrinsic factor affecting the growth and deposition of fat cells in pigs.In this study,we mainly investigated the mechanism of KDR gene promoter region variation on intramuscular fat percentage,through extracting the DNA of these samples and using AS-PCR technology to KDR gene known SNP tag effect sites,determine the relationship between this site with intramuscular fat percentage.The main results of this study are as follows:1.The predicted mean backfat thickness was significantly positively correlated with the average mean backfat thickness(0.871,P<0.01).P1,P2 and P3 predicted backfat thickness and real P1,P2 and P3 backfat thickness correlation were 0.765(P<0.01),0.770(P<0.01)and 0.781(P<0.01).The results of the eight methods showed that method three had the highest correlation and the correlation coefficient "r" was 0.799(P<0.01).The results of verifying predicted model of method three through 63 Erhualian pigs showed that the correlation coefficient between predicted intramuscular fat percentage and the actual intramuscular fat percentage was 0.643(P<0.01).2.Correlation cofficient between body weight,body length,body height,abdominal circumference and tube circumference and actual backfat thickness were 0.647(P<0.01),0.522(P<0.01),0.295(P<0.01),0.506(P<0.01)and 0.077 respectively,and the correlation cofficient with the actual intramuscular fat percentage were 0.151,0.199,0.029,0.091,0.328(P<0.05)respectively.The results showed that the correlation between body weight and backfat thickness was the highest and strongly correlated.There was no correlation between tube circumference and backfat thickness.The correlation between tube circumference and intramuscular fat percentage was the highest and moderate correlated significantly,the other indicators were not correlated with actual intramuscular fat percentage.It indicated that weight was most strongly related to backfat thickness,while tube circumference was most strongly related to intramuscular fat percentage.3.Through the promoter region upstream of the KDR gene c.-1337A>G of tag site for AS-PCR typing and the site of upstream and downstream 200 bp fragment sequencing showed 12 bases downstream from the c.-1337A>G there is also a mutation in c.-1324C>T,found by comparing the both in complete linkage status.And the tag effect site of the base distribution pattern is different,the corresponding individual intramuscular fat percentage and backfat thickness is not the same.The results showed that homozygous GT/GT type had the highest intramuscular fat percentage,while the heterozygous AC/GT type had the lowest intramuscular fat percentage,it significantly increased intramuscular fat percentage compared with homozygous GT/GT type and heterozygous AC/GT type.