The meat of local livestock breeds often has unique qualities and flavors. In this study, three Shanghai native pig breeds (MSZ, SWT, and SHB) exhibited better meat quality traits than globalized commercial pig breeds (DLY). Subsequently, metabolomic and lipidomic differences in the longissimus dorsi (L) and gluteus (T) muscles of the Shanghai native pig breeds and DLY pig breed were compared using liquid chromatography–mass spectrometry (LC–MS). The results demonstrated that the metabolites mainly consisted of (28.16%) lipids and lipid-like molecules, and (25.87%) organic acids and their derivatives were the two most dominant groups. Hundreds of differential expression metabolites were identified in every compared group, respectively. One-way ANOVA was applied to test the significance between multiple groups. Among the 20 most abundant differential metabolites, L-carnitine was significantly different in the muscles of the four pig breeds (p-value = 7.322 × 10⁻¹¹). It was significantly higher in the L and T muscles of the two indigenous black pig breeds (MSZ and SWT) than in the DLY pigs (p-value < 0.001). Similarly, lipidomic analysis revealed the PA (18:0/18:2) was significantly more abundant in the muscle of these two black breeds than that in the DLY breed (p-value < 0.001). These specific metabolites and lipids might influence the meat quality and taste properties and lead to customer preferences. Therefore, this study provided insights into the characterization of meat metabolites and lipids in Shanghai native pig breeds.

Chinese local pig breeds have unique meat flavor. In this study, we investigated the meat quality traits and the characteristics of the nutritional flavor substances such as amino acids (AAs), fatty acids (FAs), thiamine (Vitamin B1, VB1), and inosine monophosphate (IMP) in four Shanghai local pig breeds (MMS, SW, PD, and SHW) and the commercial crossbred Duroc × Landrace × Yorkshire (DLY) breed. The results showed that the intramuscular fat (IMF) and protein content in the longissimus dorsi muscle (L) of Shanghai local breeds, especially Shanghai MMS and PD breeds, were significantly higher than those of the DLY breed (p-value < 0.01). The inter-breed differences in amino acid (AA) content were even more significant in the gluteal muscle (G). Total amino acids (TAAs), flavor amino acids (FAAs), and essential amino acids (EAAs) were significantly higher in the G muscle of the four Shanghai local breeds than that in the DLY breed. The results for fatty acids (FAs) revealed that the differences in polyunsaturated fatty acids (PUFAs) were all highly significant (p-value < 0.0001), especially for the MMS breed, where the content of PUFAs in the L and G muscle amounted to (14.86 ± 2.06) g/100 g and (14.64 ± 2.83) g/100 g, respectively, which were significantly higher than those of other breeds. The MMS breed was also found to have the highest IMP content and the lowest thiamine (VB1) content among several pig breeds. Therefore, these differences in meat nutritional flavor substances provide new insights into the characterization of meat flavor in Shanghai local pig breeds.

The aim of this study was to identify effective genetic markers for the Antigen Processing Associated Transporter 1 (TAP1), α (1,2) Fucosyltransferase 1 (FUT1), Natural Resistance Associated Macrophage Protein 1 (NRAMP1), Mucin 4 (MUC4) and Mucin 13 (MUC13) diarrhea-resistance genes in the local pig breeds, namely Shanghai white pigs, Fengjing pigs, Shawutou pigs, Meishan pigs and Pudong white pigs, to provide a reference for the characterization of local pig breed resources in Shanghai. Polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLR) and sequence sequencing were applied to analyze the polymorphisms of the above genes and to explore the effects on the immunity of Shanghai local pig breeds in conjunction with some immunity factors. The results showed that both TAP1 and MUC4 genes had antidiarrheal genotype GG in the five pig breeds, AG and GG genotypes of the FUT1 gene were detected in Pudong white pigs, AA antidiarrheal genes of the NRAMP1 gene were detected in Meishan pigs, the AB type of the NRAMP1 gene was detected in Pudong white pigs, and antidiarrheal genotype GG of the MUC13 gene was only detected in Shanghai white pigs. The MUC13 antidiarrhea genotype GG was only detected in Shanghai white pigs. The TAP1 gene was moderately polymorphic in Shanghai white pigs, Fengjing pigs, Shawutou pigs, Meishan pigs and Pudong white pigs, among which TAP1 in Shanghai white pigs and Shawutou pigs did not satisfy the Hardy–Weinberg equilibrium. The FUT1 gene of Pudong white pigs was in a state of low polymorphism. NRAMP1 of Meishan pigs and Pudong white pigs was in a state of moderate polymorphism, which did not satisfy the Hardy–Weinberg equilibrium. The MUC4 genes of Shanghai white pigs and Pudong white pigs were in a state of low polymorphism, and the MUC4 genes of Fengjing pigs and Shawutou pigs were in a state of moderate polymorphism, and the MUC4 genes of Fengjing pigs and Pudong white pigs did not satisfy the Hardy–Weinberg equilibrium. The MUC13 gene of Shanghai white pigs and Pudong white pigs was in a state of moderate polymorphism. Meishan pigs had higher levels of IL-2, IL-10, IgG and TNF-α, and Pudong white pigs had higher levels of IL-12 than the other pigs. The level of interleukin 12 (IL-12) was significantly higher in the AA genotype of the MUC13 gene of Shanghai white pigs than in the AG genotype. The indicator of tumor necrosis factor alpha (TNF-α) in the AA genotype of the TAP1 gene of Fengjing pigs was significantly higher than that of the GG and AG genotypes. The indicator of IL-12 in the AG genotype of the Shawutou pig TAP1 gene was significantly higher than that of the GG genotype. The level of TNF-α in the AA genotype of the NRAMP1 gene of Meishan pigs was markedly higher than that of the AB genotype. The IL-2 level of the AG type of the FUT1 gene was obviously higher than that of the GG type of Pudong white pigs, the IL-2 level of the AA type of the MUC4 gene was dramatically higher than that of the AG type, and the IgG level of the GG type of the MUC13 gene was apparently higher than that of the AG type. The results of this study are of great significance in guiding the antidiarrhea breeding and molecular selection of Shanghai white pigs, Fengjing pigs, Shawutou pigs, Meishan pigs and Pudong white pigs and laying the foundation for future antidiarrhea breeding of various local pig breeds in Shanghai.

To address the safety problems posed by the transportation of boar semen using LN, this study was conducted on the short-term storage of frozen boar semen in dry ice (−79 °C). Boar semen frozen in LN was transferred to dry ice, kept for 1 day, 3 days, 5 days, 7 days, or 8 days, and then moved back to LN. The quality of frozen semen stored in LN or dry ice was determined to evaluate the feasibility of short-distance transportation with dry ice. The results showed that 60 °C for 8 s was the best condition for thawing frozen semen stored in dry ice. No significant differences in spermatozoa motility, plasma membrane integrity, or acrosome integrity were observed in semen after short-term storage in dry ice compared to LN (p > 0.05). There were no significant changes in antioxidant properties between storage groups either (p > 0.05). In conclusion, dry ice could be used as a cold source for the short-term transportation of frozen boar semen for at least 7 days, without affecting sperm motility, morphological integrity, or antioxidant indices.

This study developed a 60K single-nucleotide polymorphism (SNP) liquid-phase chip (‘Shenxin I’) based on genotyping by target sequencing (GBTS) technology. The chip was used to genotype 1451 individuals spanning five conserved local pig breeds: Fengjing (FJ), Meishan (MMS), Pudong White (PD), Shaowutou (SW), and Shanghai White (SHW), and newborn purebred Meishan offspring (MMS_New). The study assessed the genetic diversity, population structure, and genomic breed composition (GBC) of these breeds. The GBC analysis provided insights into genomic introgression within admixed individuals. Results indicate that PD and FJ breeds exhibited the higher fraction of the genome covered by runs of homozygosity (F_ROH) and slower linkage disequilibrium (LD) decay rate, suggesting higher genetic inbreeding level in these two breeds. The study conducted genetic distance of identity-by-state (IBS) analysis and molecular pedigree construction for the MMS population. Subsequently, purebred mating was implemented by selecting boars from different pedigrees to mate with sows and excluding individuals with high inbreeding coefficients from the breeding program. This resulted in a significant reduction in the overall inbreeding level of the born progeny and an increase in genetic diversity compared to the original population. Consequently, the study concludes that utilizing liquid-phase chip technology for genotyping, constructing molecular pedigrees, and optimizing mating combinations in small populations of locally conserved pig breeds contributes to enhancing the conservation effectiveness.

This study combined liquid-phase chip technology with a genome-wide association study (GWAS) to identify candidate functional genes for litter size in Meishan pigs. Genotyping of 198 Meishan sows using the “Shenxin No. 1” 60K porcine SNP chip, followed by quality control with PLINK v1.90, yielded 31,430 autosomal SNPs. Principal component analysis revealed no significant population stratification. Using a mixed linear model in GEMMA (v 0.98.1), we identified 9 significant SNP loci and 52 candidate genes on chromosomes 5 and 14, including AEBP2, P2RX2, ANKLE2, PGAM5, and EP400, which are implicated in embryonic development, ovarian function, and cell proliferation. Isolated porcine ovarian granulosa cells were validated by FSHR immunofluorescence, showing 99% purity. Overexpression of AEBP2 significantly upregulated its protein expression (Western blot) and promoted granulosa cell proliferation (CCK-8). Collectively, these results pinpoint potential candidate genomic regions and functional genes associated with litter size and suggest that AEBP2 may enhance reproductive performance by promoting granulosa cell proliferation and follicular development. This provides new targets for elucidating the genetic mechanisms underlying the high fecundity of Meishan pigs and for advancing molecular breeding efforts.