| With the improvement of people’s living standard,the demand for pork quality,taste and flavor is getting higher and higher.At present,more than 90% of the breeds bred in China’s pig breeding industry are imported lean pig breeds,which are characterized by high lean meat rate and fast growth,but low intramuscular fat(IMF)content and poor meat quality.Pork quality is one of the key problems to be solved in the development of pig industry.Our country is rich in local breed pigs(meat fat pig species),with the better meat quality traits,such as high intramuscular fat content,but lower lean meat,thicker backfat thickness,slower growth,and more subcutaneous fat,abdominal fat and other parts of the fatty deposits,greatly reduce the feed utilization efficiency of local pig breeds,severely restricted the comprehensive utilization of our country’s good local pig breeds.Porcine adipose deposition is a dynamic equilibrium process.To study the dynamic deposition rule of adipose tissue in different growth stages,In particular,the rule of subcutaneous fat deposition,lipid composition and serum metabolic markers related to lipid deposition are of great significance for revealing the rule of subcutaneous fat deposition and regulating the "window period" of fat pigs,thus ensuring efficient breeding and high quality pork production.In this study,the carcass indexes,subcutaneous adipocyte area and gene expression related to lipid metabolism of Shaziling and Largewhite pigs at different growth stages(30,60,90,150,210 and 300 days of age)were compared.The rule of subcutaneous fat deposition in Shaziling pigs was analyzed.Metabolic markers related to fat deposition were screened by metabolomic,and the differential lipids related to fat deposition and the important functional genes regulating subcutaneous fat deposition and differential lipid formation were identified by lipidomics and transcriptome.The main results are as follows:1、Study on the development of subcutaneous fat deposition between Shaziling and Largewhite pigsIt was found that Shaziling pigs had stronger fat deposition ability,and the fat percentage was significantly higher than that of Largewhite pigs in all six stages,but the lean meat percentage was low.The intramuscular fat content of Shaziling pigs decreased firstly and then increased with the increase of age.Statistical analysis of cell area showed that subcutaneous adipocyte area increased with age,and the average area presented two-phase distribution.The critical window for gene regulation of subcutaneous fat development period was 60-90 days of age,and the key window period was 90-150 days of age for subcutaneous fat deposition.2.Study on serum metabolites related to lipid deposition in Shaziling pigs and Largewhite pigsThe results of serum metabolomics showed that the main metabolites were lipids and analogues,organic acids and derivatives.Different metabolites are mainly involved in the synthesis and metabolism of fatty acids,amino acids and other processes,and affect the PPAR signaling pathway and m TOR signaling pathway related to fatty differentiation polyester.The correlation analysis between serum metabolites and lipid deposition traits showed that creatinine level was closely related to backfat thickness,which could be used as a potential metabolic marker to predict backfat thickness.Serum l-carnitine level can be a metabolic marker of intramuscular fat content.3.Differences in subcutaneous lipid composition between Shaziling and Largewhite pigsLipidomics analysis showed that there were significant differences in lipid composition between Shaziling and Largewhite pigs at 150,210 and 300 days of age,and the main difference lipids were glycerophospholipids.In the comparison of different pig breeds at the same stage,the common difference lipid subclass was phosphatidylglycerol(PG),and the content of Shaziling pigs was significantly lower than that of Largewhite pigs.The results of acyl chain composition showed that the percentage of monounsaturated fatty acids(MUFAs)in subcutaneous adipose tissues of Shaziling pigs was significantly higher than that of Largewhite pigs and polyunsaturated fatty acids(PUFAs)was significantly lower than that of Largewhite pigs.The changes of lipid composition in subcutaneous fat showed that the contents of different lipid class,such as PC and PG,decreased significantly with age.4.Transcriptome study of subcutaneous fatbetween Shaziling and Largewhite pigsTranscriptome sequencing results showed that there were 3716 different genes in four stages(30,90,150 and 300 days of age)between Shaziling pigs and Largewhite pigs.At 30 days of age,there were 1028 different expressed genes,of which 90 different expressed genes were related to lipid deposition and metabolism,and were enriched in adipocyte differentiation.At 90 days of age,there were 1939 different expressed genes.Among them,179 genes were associated with lipid deposition and metabolism,and were enriched in lipid metabolism and fatty acid biosynthesis.There were 1498 different expressed genes at 150 days of age,among which 135 different expressed genes were related to lipid deposition and metabolism and were enriched in lipid metabolism and phospholipid binding processes.There were 884 different expressed genes at 300 days of age,among which 75 different expressed genes were related to lipid deposition and metabolism and were enriched in lipid metabolism and lipid decomposition.The expression levels of 73 genes were significantly different in the four stages.The expression levels of CDS1,LPGAT1 and other genes in the phospholipid metabolism pathway were significantly lower in Shaziling pigs than in Largewhite pigs,which may be important regulatory genes regulating subcutaneous fat deposition and differential lipid PG production.In conclusion,this study clarified the subcutaneous adipose tissue deposition rule and critical window period in different growth stages of Shaziling pigs and Largewhite pigs,and explored the blood metabolic markers related to adipose deposition.The differences in lipid composition and the important genes regulating subcutaneous fat deposition and lipid metabolism were analyzed.It lays a foundation for the regulation of lipid deposition,especially backfat thickness,of excellent fat-fat pigs such as Shaziling pigs,and is also of great significance for the protection and utilization of germplasm resources of Shaziling pigs and healthy and efficient breeding. |
