This study aimed to investigate the roughage tolerance of different breeds of pigs. Mashen (MS; n = 80) and Duroc × Landrace × Yorkshire (DLY; n = 80) pigs with an initial body weight of 20 ± 0.5 kg were randomly allotted to four diet treatments (n = 20 of each breed) with different fiber levels. The dietary fiber levels increased by adding 0-28% soybean hull to replace corn and soybean meal partially. According to the neutral detergent fiber (NDF) level, all treatments were MS_9N (9% NDF), MS_13.5N (13.5% NDF), MS_18N (18% NDF), MS_22.5N (22.5% NDF), DLY_9N (9% NDF), DLY_13.5N (13.5% NDF), DLY_18N (18% NDF), and DLY_22.5N (22.5% NDF). The growth performance, nutrient digestibility, intestinal morphology, and colonic short-chain fatty acids of pigs were measured. The colonic microbiota and metabolome were analyzed using 16S rDNA gene sequencing and UHPLC-MS/MS. The average daily gain and daily feed intake of MS_18N and DLY_13.5N were increased compared with MS_9N and DLY_9N, respectively (P < 0.05). The digestibility of NDF and acid detergent fiber of MS_18N were greater than that of MS_9N (P < 0.05). The villus height /crypt depth (V/C) of the duodenum, jejunum, and ileum of MS_18N and MS_22.5N increased compared with MS_9N (P < 0.05), and the V/C of duodenum and ileum of DLY_22.5N decreased compared with DLY_9N (P < 0.05). The colonic acetic acid and butyric acid concentrations of MS_18N were greater than those of MS_9N and MS_13.5N (P < 0.05). The concentrations of acetic acid and butyric acid of DLY_13.5N increased compared with DLY_9N (P < 0.05). Prevotellaceae_NK3B31_group in MS_18N and Methanobrevibacter in MS_22.5N increased compared with other groups (P < 0.05). Increasing the NDF level in diets changed the lipid and amino acid metabolism pathways. In conclusion, appropriate fiber levels can promote pigs’ growth performance and intestinal development. The optimum fiber level of the MS pig was 18% NDF, while that of the DLY pig was 13.5%. This result indicates that MS pigs had strong fiber fermentation ability due to the higher abundance of the colonic microbiota that could fully ferment fiber and provide extra energy to MS pigs.

The two breeds, Mashen (MS, a northern China breed) and Large White (LW, a western lean breed) pigs, show important phenotypic differences in growth, adaptability, intramuscular fat (IMF) content and energy metabolism since early developmental stage. The main aim of this study was the evaluation of longissimus thoracis muscle transcriptome profile of both genetic types to identify genes, pathways responsible for their differentiated phenotype. Longissimus thoracis of MS and LW pigs were sampled at 0 day (early stage), 90 days (middle stage), and 180 days (later stage) after birth. A total of 3,487 differentially expressed genes (DEGs) were identified at the three time points. Sample clustering analysis revealed the relatively slower growth rate of MS than LW pigs. Gene expression pattern analysis revealed that multicellular organism growth genes (GHSR, EZR, FOXS1, DRD2, SH3PXD2B, CSF1, TSHR) were involved in the fast growth rate of LW pigs at early stage. Furthermore, DEGs (ACACA, ACSF3, OXSM, CBR4, HSD17B8) functionally related to fatty acid synthesis revealed that IMF accumulation occurred around 90 days and up to 180 days. These DEGs provided valuable resource to study the phenotypic difference in longissimus thoracis muscle between MS and LW pigs.

The aim of this study was to select the candidate genes affecting meat quality and preliminarily explore the related molecular mechanisms in the Mashen pig. The present study explored genetic factors affecting meat quality in the Mashen pig using RNA sequencing (RNA-Seq). We sequenced the transcriptomes of 180-day-old Mashen and Large White pigs using longissimus dorsi to select differentially expressed genes (DEGs). The results indicated that a total of 425 genes were differentially expressed between Mashen and Large White pigs. A gene ontology enrichment analysis revealed that DEGs were mainly enriched for biological processes associated with metabolism and muscle development, while a Kyoto encyclopedia of genes and genomes analysis showed that DEGs mainly participated in signaling pathways associated with amino acid metabolism, fatty acid metabolism, and skeletal muscle differentiation. A MCODE analysis of the protein-protein interaction network indicated that the four identified subsets of genes were mainly associated with translational initiation, skeletal muscle differentiation, amino acid metabolism, and oxidative phosphorylation pathways. Based on the analysis results, we selected glutamic-oxaloacetic transaminase 1, malate dehydrogenase 1, pyruvate dehydrogenase 1, pyruvate dehydrogenase kinase 4, and activator protein-1 as candidate genes affecting meat quality in pigs. A discussion of the related molecular mechanisms is provided to offer a theoretical basis for future studies on the improvement of meat quality in pigs.

Intramuscular fat (IMF) is critical pork meat quality; however, its content is relatively low in commercial pig breeds. The objective of this experiment was to investigate the difference in intramuscular adipogenesis between Mashen and Large White pigs. 12 male Mashen and Large White piglets (six in each breed) were used, and longissimus dorsi muscle was sampled for analysis. The results showed that back fat thickness (p < .01) and leaf fat weight (p < .05) were increased in Mashen pigs. Moreover, the IMF contents were greater in Mashen pigs (p < .01). With exception of sterol regulatory element-binding protein 1, mRNA expression of other adipogenic markers, including Zinc finger protein 423 (p < .05), platelet-derived growth factor receptor α (p < .05), CCAAT enhancer binding protein β (C/EBPβ, p < .05), C/EBPα (p < .05) and peroxisome proliferator-activated receptor γ (PPARγ, p < .01) were greater in Mashen pigs; consistently, protein abundance of both C/EBPα (p < .01) and PPARγ (p < .05) were also greater. Both mRNA expression of fatty acid synthase (FAS) (p < .01) and its activity (p < .05) were elevated in Mashen pigs, whereas no difference of acetyl-CoA carboxylase activity was observed. In addition, protein content of fatty-acid binding protein 4 (FABP4) was elevated in Mashen pigs. The malate dehydrogenase activity was greater (p < .05) and hormone-sensitive lipase activity was lower in Mashen pigs. In summary, IMF content was enhanced in Mashen pigs, which at least partly through enhancing intramuscular adipogenesis.