| Liangshan pig belongs to one population of Wujin pig, mainly distributed in Yi Autonomous Prefecture of Liangshan. Liangshan pig has its own unique population characteristics compare to other groups (Kele pigs, Fadi pigs, Dahe pigs, Zhaotong pigs), because its suffered with geographical isolation and different artificial selection in long-term. At present, with the rapid and large-scale development of the swine industry, the population of Chinese native pig is declining and being in danger of extinction. Liangshan pig is a typical Chinese native pig breed with many merits suach as early sexual maturity, coarse feeding resistance and wonderful meat quality. It is necessary to protect Liangshan pig and utilize this good germplasm resource. However, due to the differences in genetic background, there were some difference varieties of production parameters. The optimal production parameter of each type is the basis of the development and utilization. The objective of this study was to collected the growth development data of 305 Liangshan pigs to fitting the growth curve of Liangshan pig, found out their suitable slaughter weight (growth inflection point) and analyzed the correlation between carcass, meat quality and growth curve. To explore the native pig genetic mechanism of the growth curve we also make transcriptome sequencing at the growth inflection point and before and after it. Then carries on the enrichment and functional analysis of differences expression genes, provides reliable theoretical and scientific basis for the development and utilization of liangshan pig. The main conclusions are as follows:Three non-linear models were utilized to fit the growth curve of Liangshan pig, found the growth of Liangshan pig fitted the typical S-curve. According to the fitting growth curve, the growth turning point of Liangshan pig was 193.33d within the weight of 62.61kg and the highest daily gain of 629.69g.The carcass traits research on the ten different development stages of liangshan pig showed that: the average backfat, the loin area, sebum percentage and the dressing percentage were increased with the the growth of liangshan pig. Rate of lean and bone was increased weight and after decreased, and reached the maximum near the growth point. All of above consistent with the result of the lean meat percentage, showed that after the growth turning point of Liangshan pig was main with fat deposition.The meat quality traits research on the seven different development stages of liangshan pig showed that:the pH1(45 min) after slaughter), pH2 (24 h after slaughter), the red of a value, moisture holding capacity and marbling of longissimus dorsi were relatively high. All the traits significantly improved after growth inflection point (p< 0.05), showed that early slaughtering Liangshan pig not conducive to the formation of good meat quality traits.The nutrition composition research on the seven different development stages of liangshan pig shows that:the muscle of Liangshan pig contains abundant free amino acids and fatty acids. The fatty acid content, composition and P:S were increased with body weight, but free amino acid was reached the maximum when growth inflection point.Using RNA-seq determined nine muscle transcriptome of liangshan pig, get a total of about 117692255 reads and 5.89 Gb (gigabases) of available data.21,966 activity gene were detected before growth inflection point (BIP),21,331gene were detected at growth inflection point (UIP),20,996 gene were detected after growth inflection point (AIP).20,139 gene were coexpression at the three stages, 747gene specificity expressed at BIP,364 gene specificity expressed at UIP,261 gene specificity expressed at AIP. total of 380(27.70%) specific expression were significantly enriched in the growth development and the meat quality related QTL regions.Gene difference analysis selected 775 differentially expressed genes in the BIP and UIP. The BIP difference transcription are main enrichment to immune system pathways; the UIP difference transcription are main enrichment to Cell transcriptional activity regulation pathways; Only 271 differences gene transcription exist in both AIP and UIP, the AIP difference transcription are main enrichment to amino acids and carbohydrate metabolic pathways; the UIP difference high expression transcription are main enrichment to Collagen and bone development related pathways.The analysis of innate immune development related gene expression showed that:the C1QA、 C1QB、C1QC expression in BIP are 2-5 times higher than UIP and AIP; RNA polymerase II transcription factors and mitochondrial genes are higher experssion in UIP; The genes are related to synthesize intramuscular fat and fatty acid are higher expression in AIP.Combination with the phenotypic data of liangshan pig showed that:Liangshan pig is mainly on the improvement of the immune system before the growth inflection point; Liangshan pig has the fastest growth rate in inflection point and the function of mitochondria and transcriptional activity of cell are enhenced. Meanwhile, the skeletal maturity also in development. The meat qulity traits, such as fitty acid, amino acid, carbohydrate metabolism, are in developing on AIP.RNA-seq results are verified through the Q-PCR, and had high correlation between them(r> 0.75, P< 0.05), illustrate that RNA-seq results are accurate and reliable.Through this study, we further perfecting the production parameters of liangshan pig, found the liangshan pig growth inflection point and have a further research on the genetic mechanism of difference biological function at, before and after the growth inflection point of Liangshan pig. This has great significance guiding for the actual production and utilization of liangshan pig, also provides the reference basis for the storage and development of Chinese native pig breeds. |
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