Research On The Application Of Computed Tomography For In Vivo Estimation Of Carcass And Meat Quality Traits In Duroc Boars

The pig industry is a major industry that affects the livelihood of the nation,and China is the world’s largest pig producer and pork consumer.The selection and breeding of breeding pigs is at the core of the development of live pigs,and accurate in vivo estimation of the carcass and meat quality traits of breeding pigs is essential to guide the selection and breeding of good breeds.However,China’s breeders have long relied on imports,and the idea of"emphasizing introduction,neglecting breeding"has not only led China into a vicious circle of"introduction-maintenance-degradation-re-introduction",but also restricted the development of trait determination technology for breeding pigs in China.At present,pig breeding enterprises in China use B-ultrasound machines to determine backfat thickness,loin eye depth,loin eye area,and intramuscular fat（IMF）content to assess the carcass and meat quality traits of breeding pigs,but the accuracy of the measurement technology is not high,which affects the accurate selection and feeding of breeding pigs.Computed Tomography（CT）is a non-invasive imaging technique used primarily for medical diagnosis.Its principle is based on the difference in attenuation of X-rays through tissues,with denser tissues producing greater attenuation of X-rays,thus allowing CT to separate different tissues.With the steady development in the field of CT equipment and image analysis,CT is also gradually being used in live animals and meat determination in some western countries to determine the body composition and meat quality of live animals and carcasses.CT measurement techniques avoid losses and environmental pollution caused by slaughter,but also enable well-tested breeding pigs to fulfill their breeding value and accelerate the genetic progress of the herd.Nevertheless,CT in vivo assessment of economic traits of breeding pigs is in the initial stage of development in China,and its in-depth exploration and application are particularly important.In this study,Duroc boars were selected and scanned in vivo using CT.The images were subjected to thin-layer reconstruction and denoising,pseudo-colour enhancement,multi-planar reconstruction and image segmentation to assess carcass and meat quality traits,with a view to providing a scientific basis for selection and breeding as well as fine feeding management of breeding pigs in China.The main results obtained in this study were as follows:1.A CT in vivo accurate assessment technique for the determination of carcass and meat quality traits of breeding pigs has been developed,including the process of pig anaesthesia,scanning,and image analysis.2.CT allows accurate assessment of carcass traits in breeding pigs.Carcass traits of breeding pigs were determined using CT,including carcass composition,backfat thickness,loin eye depth,loin eye area,carcass straight length,and carcass sloping length.There was no significant difference between CT and measured carcass composition,backfat thickness,loin eye depth,carcass straight length,and carcass sloping length（P>0.05）.When measuring the backfat thickness at the thoracolumbar junction,the difference between B-ultrasound and the actual measurement was significant（P<0.05）,while the difference between CT and the actual measurement was not significant（P>0.05）.3.A regression equation was developed using partial least squares regression to predict the lean percentage of breeding pig carcasses based on CT image parameters.y=56.0691-0.1330x₁-0.0346x₂-0.45543x₃-0.1478x₄+0.0406x₅+0.0739x₆+0.0631x₇+0.0838x₈y is the predicted carcass leanness,x₁ is the backfat thickness at the thickest shoulder,x₂is the backfat thickness between the third and fourth last ribs,x₃ is the backfat thickness at the thoracolumbar junction,x₄ is the backfat thickness at the lumbar-sacral junction,x₅ is the loin eye depth between the third and fourth last ribs,x₆ is the loin eye area between the third and fourth last ribs,x₇ is the carcass straight length,and x₈ is the carcass sloping length.The root mean square error of prediction（RMSEP）was 0.1472,and the coefficient of determination（R²）was 0.983.4.CT allows accurate assessment of meat quality traits in breeding pigs.Intramuscular fat content was assessed by CT in different areas,including the longissimus thoracis,gluteus medius,biceps femoris,and semimembranosus.There was no significant difference between CT and actual measurement in evaluating the intramuscular fat content of the longissimus thoracis,gluteus medius,and semimembranosus（P>0.05）.5.By the volume-rendering techinique（VRT）,a three-dimensional atlas of breeding pigs was constructed and the carcass was virtually divided precisely into left and right parts on the three-dimensional atlas.In summary,this study has developed a CT in vivo accurate measurement technique for assessing carcass and meat quality traits in breeding pigs,which can be applied in core breeding farms to guide the selection of breeding pigs.