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In this study, the differences in protein profiles between the livers of Shannan Tibetan pigs (SNT), Linzhi Tibetan pigs (LZT) and Jiuzhaigou Tibetan pigs (JZT) were comparatively analyzed by tandem mass spectrometry-labeling quantitative proteomics. A total of 6804 proteins were identified: 6471 were quantified and 1095 were screened as differentially expressed proteins (DEPs). Bioinformatics analysis results show that, compared with JZT livers, up-regulated DEPs in SNT and LZT livers mainly promoted hepatic detoxification through steroid hormone biosynthesis and participated in lipid metabolism to maintain body energy homeostasis, immune response and immune regulation, while down-regulated DEPs were mainly involved in lipid metabolism and immune regulation. Three proteases closely related to hepatic fatty acid oxidation were down-regulated in enzymatic activity, indicating higher levels of lipid oxidation in SNT and LZT livers than in JZT livers. Down-regulation of the expression of ten immunoglobulins suggests that JZT are more susceptible to autoimmune diseases. It is highly likely that these differences in lipid metabolism and immune-related proteins are in response to the ecological environment at different altitudes, and the findings contribute to the understanding of the potential molecular link between Tibetan pig livers and the environment.

Tibet pig is a unique native breed in the plateau of China, which has good adaptation to the harsh climate of high land and resistance to diseases and crude feeding. However, its reproductive rate is low. The objectives of this study were to search for the polymorphisms of estrogen receptor (ESR), follicle-stimulating hormone (FSHb), prolactin receptor (PRLR), and retinol binding protein 4 (RBP4) in Tibet pig and to analyze the effects of these variants and their combination genotypes on reproductive traits. The results showed that the effects of FSHb, ESR, and PRLR genes were significant in the Tibet pig population, and the effective genotypes of the three genes for reproductive traits were BB, BB, and AA, respectively. There were two genotypes for RBP4 gene in Tibet pig, which did not have significant effect on the reproductive traits. The optical genotype of FSHb-ESR-PRLR is BB-BB-AA, which is more effective on reproductive traits than any single gene in Tibet pig.

Tibet pig is a special Chinese indigenous pig breed, which could survive in high-altitude areas of Tibet. In the present study, the genotypes of ESR, FSHbeta, and PRLR gene, the three known major genes of reproductive traits, were identified in 202 Tibet pig individuals. The results showed that the predominant genotypes of ESR, FSHbeta, and PRLR gene were BB, AB and AA, respectively. The genotype frequencies of the three genes were in Hardy-Weinberg equilibrium. The frequencies of desired alleles of the three genes were higher than those of other alleles, which indicated that Tibet pig had a good potential for improving reproductive traits.