Longissimus Dorsi Muscle Of Pigs Research Articles

The Role of the MYL4 Gene in Porcine Muscle Development and Its Molecular Regulatory Mechanisms.

Muscle growth stands as a pivotal economic trait within pig production, governed by a complex interplay of multiple genes, each playing a role in its quantitative manifestation. Understanding the intricate regulatory mechanisms of porcine muscle development is crucial for enhancing both pork yield and quality. This study used the GSE99749 dataset downloaded from the GEO database, conducting a detailed analysis of the RNA-seq results from the longissimus dorsi muscle (LD) of Tibetan pigs (TP), Wujin pigs (WJ) and large white pigs (LW) at 60 days of gestation, representing diverse body sizes and growth rates. Comparative analyses between TPvsWJ and TPvsLW, along with differential gene expression (DEG) analysis, functional enrichment analysis, and protein-protein interaction (PPI) network analysis, revealed 1048 and 1157 significantly differentially expressed genes (p < 0.001) in TPvsWJ and TPvsLW, respectively. With stricter screening criteria, 37 DEGs were found to overlap between the 2 groups. PPI analysis identified MYL5, MYL4, and ACTC1 as the three core genes. This article focuses on exploring the MYL4 gene. Molecular-level experimental validation, through overexpression and interference of the MYL4 gene combined with EDU staining experiments, demonstrated that overexpression of MYL4 significantly promoted the proliferation of porcine skeletal muscle satellite cells (PSMSC), while interference with MYL4 inhibited their proliferation. Furthermore, by examining the effects of overexpressing and interfering with the MYL4 gene on the muscle hypertrophy marker Fst gene and the muscle degradation marker FOXO3 gene, the pivotal role of the MYL4 gene in promoting muscle growth and preventing muscle degradation was further confirmed. These findings offer a new perspective on the molecular mechanisms behind porcine muscle growth and development, furnishing valuable data and insights for muscle biology research.

Effects of adding bile acids to dietary storage japonica brown rice on growth performance, meat quality, and intestinal microbiota of growing-finishing Min pigs.

This study investigated the effects of storage japonica brown rice (SJBR) and bile acids (BA) on the growth performance, meat quality, and intestinal microbiota of growing-finishing Min pigs. A total of 24 healthy Min pigs with a similar body weight of 42.25 ± 2.13 kg were randomly divided into three groups with eight replicates of one pig each. The groups were as follows: CON (50% corn), SJBR (25% corn +25% SJBR), and SJBR + BA (25% corn +25% SJBR +0.025% hyodeoxycholic acid). The experimental period lasted from day 90 (the end of the nursery phase) to day 210 (the end of the finishing phase). The results showed the following: (1) Compared with the CON group, there was no significant difference in the average daily gain (ADG) and average daily feed intake (ADFI) of the SJBR and SJBR + BA groups, and the feed conversion ratio (FCR) was significantly decreased (p < 0.05). (2) Compared with the CON group, the total protein (TP) content in the serum was significantly increased, and the blood urea nitrogen (BUN) content was significantly decreased (p < 0.05) in the SJBR and SJBR + BA groups; moreover, HDL-C was significantly higher by 35% (p < 0.05) in the SJBR + BA group. (3) There were no significant differences in carcass weight, carcass length, pH, drip loss, cooking loss, and shear force among the groups; the eye muscle area was significantly increased in the SJBR group compared with the CON group (p < 0.05); back fat thickness was significantly decreased in the SJBR + BA group compared with the SJBR group (p < 0.05); and the addition of SJBR significantly increased the mRNA expression of MyHC I in the longissimus dorsi (LD) muscle of growing-finishing Min pigs (p < 0.05). (4) The cecal bacteria were detected using 16S rDNA, and the proportion of Lactobacillus was increased gradually at the genus level, but there was no significant difference among the different groups. In conclusion, 25% SJBR can improve the growth performance and increase the abundance of intestinal beneficial bacteria, and based on this, adding bile acids can reduce the back fat thickness of growing-finishing Min pigs.

Subtherapeutic Kitasamycin Promoted Fat Accumulation in the Longissimus Dorsi Muscle in Growing-Finishing Pigs.

Kitasamycin (KM), a broad-spectrum macrolide antibiotic, has implications for growth performance and residue in animals and humans. This study aimed to explore the effects of different KM doses on intramuscular fat accumulation, cecal microflora, and short-chain fatty acids (SCFAs) using a growing-finishing pig model. Forty-two pigs were divided into three groups: control, subtherapeutic KM (50 mg/kg, KM50), and therapeutic KM (200 mg/kg, KM200) diets over 8 weeks. KM50 led to increased back fat thickness, fat content in the longissimus dorsi muscle (LM), and elevated plasma total cholesterol (TC) levels (p < 0.05), supported by upregulated lipid synthesis gene expression (Acc1, Fas, Scd1) (p < 0.05) in the LM. KM50 altered cecal microflora, reducing Lactobacillus spp. and Bifidobacterium spp. abundance, while increasing SCFA concentrations (acetic acid, propionic acid, total SCFAs) (p < 0.05). KM200 had minimal effects on intestinal weight and density, with increased apparent digestibility of nutrients. These findings highlight the dose-dependent impact of KM on intramuscular fat deposition. Subtherapeutic KM induced ectopic fat deposition, emphasizing potential risks in disease treatment for humans and animals.

TMT-labeled quantitative malonylome analysis on the longissimus dorsi muscle of Laiwu pigs reveals the role of ACOT7 in fat deposition

The Laiwu pig is an indigenous fatty pig breed distributed in North China, characterized by an extremely high level of intramuscular fat (IMF) content (9% ∼ 12%), but the regulatory mechanism underlying intramuscular fat deposition in skeletal muscle is still unknown. In this study, the TMT-labeled quantitative malonylome of the longissimus dorsi muscle in Laiwu pigs at the fastest IMF deposition stage (240 d vs 120 d) was compared to analyze the molecular mechanism of IMF variation in pigs. In Laiwu pigs aged 240 days/120 days, we identified 291 malonylated lysine sites across 188 proteins in the longissimus dorsi muscle. Among these, 38 sites across 31 proteins exhibited differential malonylation. Annotation analysis and enrichment analysis were performed for differentially malonylated proteins (DMPs). These DMPs were mainly clustered into 12 GO functional categories accounting for 5 biological processes, 4 cellular components and 3 molecular functions, and 2 signaling pathways by KEGG enrichment analysis. The function of differentially malonylated protein ACOT7 in the process of fat deposition was further investigated during the differentiation of 3 T3-L1 cells. The results showed that the protein level of ACOT7 in 3 T3-L1 cells decreased but the malonylated level of ACOT7 increased significantly. The malonyl-CoA that is synthesized by ACSF3 affected the malonylation level of ACOT7 in 3 T3-L1 cells. SignificanceThe intramuscular fat (IMF) content, by affecting sensory quality traits of meat, such as tenderness, flavor and juiciness, plays an important role in meat quality. Using TMT-based quantitative malonylated proteome analysis, we identified malonylated proteins in LD muscle samples in two stages (120 d and 240 d) of development and further identified differentially malonylated proteins, such as SLC25A4, ANXA5, TPM3 and ACOT7, that are associated with intramuscular fat deposition and fat metabolism in pigs. These differentially malonylated proteins could serve as candidates for elucidating the molecular mechanism of IMF deposition in pigs. In addition, we found that the malonyl-CoA in 3 T3-L1 cells is mainly synthesized by ACSF3, affecting the malonylated level of ACOT7. The study provides some data concerning the role of protein malonylation in regulating the variation in porcine IMF content.

Smartphone-based digital phenotyping for genome-wide association study of intramuscular fat traits in longissimus dorsi muscle of pigs.

Intramuscular fat (IMF) content and distribution significantly contribute to the eating quality of pork. However, the current methods used for measuring these traits are complex, time-consumingand costly. To simplify the measurement process, this study developed a smartphone application (App) called Pork IMF. This App serves as a rapid and portable phenotyping tool for acquiring pork images and extracting the image-based IMF traits through embedded deep-learning algorithms. Utilizing this App, we collected the IMF traits of the longissimus dorsi muscle in a crossbred population of Large White × Tongcheng pigs. Genome-wide association studies detected 13 and 16 SNPs that were significantly associated with IMF content and distribution, respectively, highlighting NR2F2, MCTP2, MTLN, ST3GAL5, NDUFAB1 and PID1 as candidate genes. Our research introduces a user-friendly digital phenotyping technology for quantifying IMF traits and suggests candidate genes and SNPs for genetic improvement of IMF traits in pigs.

Trimethylamine oxide supplementation differentially regulates fat deposition in liver, longissimus dorsi muscle and adipose tissue of growing-finishing pigs

Trimethylamine oxide (TMAO) is a microbiota-derived metabolite, and numerous studies have shown that it could regulate fat metabolism in humans and mice. However, few studies have focused on the effects of TMAO on fat deposition in growing-finishing pigs. This study aimed to investigate the effect of TMAO on fat deposition and intestinal microbiota in growing-finishing pigs. Sixteen growing pigs were randomly divided into 2 groups and fed with a basal diet with 0 or 1 g/kg TMAO for 149 d. The intestinal microbial profiles, fat deposition indexes, and fatty acid profiles were measured. These results showed that TMAO supplementation had a tendency to decrease lean body mass (P < 0.1) and significantly increased backfat thickness (P < 0.05), but it did not affect growth performance. TMAO significantly increased total protein (TP) concentration, and reduced alkaline phosphatase (ALP) concentration in serum (P < 0.05). TMAO increased the α diversity of the ileal microbiota community (P < 0.05), and it did not affect the colonic microbial community. TMAO supplementation significantly increased acetate content in the ileum, and Proteobacteria and Escherichia–Shigella were significantly enriched in the TMAO group (P < 0.05). In addition, TMAO decreased fat content, as well as the ratio of linoleic acid, n-6 polyunsaturated fatty acids (PUFA), and PUFA in the liver (P < 0.05). On the contrary, TMAO increased intramuscular fat content of the longissimus dorsi muscle, whereas the C18:2n6c ratio was increased, and the n-6 PUFA:PUFA ratio was decreased (P < 0.05). In vitro, 1 mM TMAO treatment significantly upregulated the expression of FASN and SREBP1 in C2C12 cells (P < 0.05). Nevertheless, TMAO also increased adipocyte area and decreased the CPT-1B expression in subcutaneous fat (P < 0.05). Taken together, TMAO supplementation regulated ileal microbial composition and acetate production, and regulated fat distribution and fatty acid composition in growing-finishing pigs. These results provide new insights for understanding the role of TMAO in humans and animals.

Integrated analysis of circRNA, lncRNA, miRNA and mRNA to reveal the ceRNA regulatory network of postnatal skeletal muscle development in Ningxiang pig.

Introduction: The development of skeletal muscle is regulated by regulatory factors of genes and non-coding RNAs (ncRNAs). Methods: The objective of this study was to understand the transformation of muscle fiber type in the longissimus dorsi muscle of male Ningxiang pigs at four different growth stages (30, 90, 150, and 210 days after birth, n = 3) by histological analysis and whole transcriptome sequencing. Additionally, the study investigated the expression patterns of various RNAs involved in muscle fiber transformation and constructed a regulatory network for competing endogenous RNA (ceRNA) that includes circular RNA (circRNA)/long non-coding RNA (lncRNA)-microRNA (miRNA)-messenger RNA (mRNA). Results: Histomorphology analysis showed that the diameter of muscle fiber reached its maximum at 150 days after birth. The slow muscle fiber transformation showed a pattern of initial decrease followed by an increase. 29,963 circRNAs, 2,683 lncRNAs, 986 miRNAs and 22,411 mRNAs with expression level ≥0 were identified by whole transcriptome sequencing. Furthermore, 642 differentially expressed circRNAs (DEc), 505 differentially expressed lncRNAs (DEl), 316 differentially expressed miRNAs (DEmi) and 6,090 differentially expressed mRNAs (DEm) were identified by differential expression analysis. Functions of differentially expressed mRNA were identified by gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). GO enrichment analysis indicates that 40 known genes and 6 new genes are associated with skeletal muscle development. Additionally, KEGG analysis shows that these genes regulate skeletal muscle development via MAPK, FoxO, Hedgehog, PI3K-Akt, Notch, VEGF and other signaling pathways. Through protein-protein interaction (PPI) and transcription factor prediction (TFP), the action mode of skeletal muscle-related genes was explored. PPI analysis showed that there were stable interactions among 19 proteins, meanwhile, TFP analysis predicted 22 transcription factors such as HMG20B, MYF6, MYOD1 and MYOG, and 12 of the 19 interacting proteins were transcription factors. The regulatory network of ceRNA related to skeletal muscle development was constructed based on the correlation of various RNA expression levels and the targeted binding characteristics with miRNA. The regulatory network included 31 DEms, 59 miRNAs, 667 circRNAs and 224 lncRNAs. conclusion: Overall, the study revealed the role of ceRNA regulatory network in the transformation of skeletal muscle fiber types in Ningxiang pigs, which contributes to the understanding of ceRNA regulatory network in Ningxiang pigs during the skeletal muscle development period.

Age-Dependent Developmental Changes of Selenium Content and Selenoprotein Expression and Content in Longissimus Dorsi Muscle and Liver of Duroc Pigs.

The trace element selenium (Se) plays a key role in development and various physiological processes, mainly through its transformation into selenoproteins. To investigate the developmental patterns of Se content and expression of selenoproteins, the liver and longissimus dorsi (LD) muscle of Duroc pigs were collected at 1, 21, 80, and 185days of age (7 pigs each age) for the determination of Se content, mRNA expression of selenoproteins, and concentrations of glutathione peroxidase (GPX), thioredoxin reductase (TrxR or TXNRD), and selenoprotein P (SELP). The results showed that age significantly affected the expression of GPX1, GPX2, GPX3, TXNRD1, TXNRD2, TXNRD3, iodothyronine deiodinases 2 (DIO2), DIO3, SELF, SELH, SELM, SELP, SELS, SELW, and selenophosphate synthetase2 (SPS2) in the liver, as well as GPX3, GPX4, TXNRD1, TXNRD2, DIO2, DIO3, SELF, SELN, SELP, SELR, SELS, and SELW in the LD muscle of Duroc pigs. The concentrations of GPX, TrxR, and SELP showed an increasing trend with age, and they were positively correlated with Se content at 1, 21, and 185days of age and negatively correlated at 80days of age, both in the liver and LD muscle. The Se content decreased at the age of 80days, especially in the LD muscle. In summary, our study revealed developmental changes in Se content and expression of selenoproteins in the liver and LD muscle of Duroc pigs at different growth stages, which provided a theoretical basis for further study of Se nutrition and functions of selenoproteins.

Dietary supplementation with vegetable oils with low n-6:n-3 polyunsaturated fatty acid ratios improves the intramuscular fat and fatty acid composition of growingfinishing pigs

This study investigated the effects of different n-6:n-3 polyunsaturated fatty acid (PUFA) ratios in pig diets using vegetable oil supplementation on growth performance, carcass characteristics, meat quality, and fatty acid composition in the longissimus dorsi muscle (LM) and subcutaneous adipose tissue (SAT) of pigs. Fiftyfour cross-bred growing pigs (Large White × Landrace × Duroc; 45.03 ± 1.72 kg) were randomly assigned to one of three isoenergetic diets: the 1) basal diet (control), 2) RAPO diet (diet supplemented with 4.5% rapeseed oil), and 3) MIXO diet (diet supplemented with 2.25% rapeseed oil and 2.25% linseed oil), with n-6:n-3 PUFA ratios of approximately 13:1, 7:1, and 2:1, respectively. The experiment lasted 42 days. The RAPO and MIXO diets did not affect the growth performance and carcass characteristics of pigs, while the content of low-density lipoprotein (LDL), triglycerides (TGs), and glucose (GLU) in the serum decreased substantially. Intramuscular fat (IMF) content increased by 19.25% and 20.11% in the LM of pigs fed the RAPO and MIXO diets, respectively, and lower cooking loss and drip loss of meat were observed only in pigs fed the MIXO diet. The RAPO and MIXO diets decreased the stearic acid and palmitoleic acid levels, increased the total PUFA levels (including those of α-linolenic and linoleic acid), and decreased the n-6:n-3 PUFA ratios in LM and SAT. However, the MIXO diet was more effective in improving the fatty acid composition. A mixed oil diet with an n6:n-3 PUFA ratio of 2:1 is an effective measure for improving meat quality.

Evaluation of dietary curcumin nanospheres as phytobiotics on growth performance, serum biochemistry, nutritional composition, meat quality, gastrointestinal health, and fecal condition of finishing pigs.

Curcumin is a bioactive functional feeding stimulant that is widely used as an additive in cuisine and animal feeds. Owing to its hydrophobic nature and low bioavailability, the nanoformulation of curcumin has recently received special attention from researchers. In this study, we investigated the effects of curcumin nanospheres (CN) on the growth performance, serum biochemistry, meat quality, intestinal immunohistochemistry, fecal malodors and microbes in finishing pigs. A total of 90 crossbred pigs (Duroc × [Yorkshire × Landrace]) with an average initial body weight of 73.77 ± 0.08 kg were randomized into 3 dietary groups in triplicate pens (10 pigs in each pen): control (CON) without supplementation of CN and the pigs in the remaining two groups were supplemented with CN at 1.0 (CN1) and 2.0 (CN2) mL/kg diet for a 40-day long experiment. The results showed that pigs fed the higher CN supplemented diet (CN2) had significantly higher final weight (FW) and weight gain (WG) than those fed the CON diet, and no significant differences were observed in the feed conversion ratio (FCR) and average daily feed intake (ADFI) after 28 days. At the end of the experiment, pigs fed the CN supplemented diet showed no significant difference in WG, ADFI or FCR compared to those on the CON diet. Overall, at the termination of the 40-day feeding trial, dietary CN had a significant effect on FW and WG, except for ADFI and FCR, in finishing pigs. After 40 days of the feeding trial, serum biochemical parameters such as glutamic-pyruvic transaminase, glutamic-oxaloacetic transaminase, triglycerides, and total cholesterol levels were significantly decreased in pigs fed the CN supplemented diet. However, high density lipoprotein levels were significantly increased in pigs fed the CN diets. Protein and lipid contents, as well as yellowness and lightness of the neck and longissimus dorsi muscles were not significantly affected by CN supplementation; however, there was a tendency to increase the redness of the longissimus dorsi muscle in pigs fed the CN2 supplemented diet compared to the CON diet. Meat grading and carcass weight significantly increased in pigs fed a higher CN supplemented diet. Fecal Escherichia coli and ammonia gas were significantly depleted in pigs fed CN diets. Histomorphological parameters, such as villus height, crypt depth and goblet cells in the jejunum of the intestine were significantly increased in pigs fed CN diet. Immunohistochemical staining showed that pro-inflammatory cytokine like tumor necrosis factor-α expression was reduced in pigs fed CN supplemented diets compared to the CON diet; however, antibodies such as immunoglobulin A and tight junction proteins such as claudin 3 were highly expressed in the intestine of pigs fed the CN diets. Overall, the results demonstrate the potential of dietary curcumin nanospheres as a nanobiotechnology tool as well as an effective feed additive for improving the performance and health status of finishing pigs.

Pig fetal skeletal muscle development is associated with genome-wide DNA hypomethylation and corresponding alterations in transcript and microRNA expression.

Fetal myogenesis represents a critical period of porcine skeletal muscle development and requires coordinated expression of thousands of genes. Epigenetic mechanisms, including DNA methylation, drive transcriptional regulation during development; however, these processes are understudied in developing porcine tissues. We performed bisulfite sequencing to assess DNA methylation in pig longissimus dorsi muscle at 41- and 70-days gestation (dg), as well as RNA- and small RNA-sequencing to identify coordinated changes in methylation and expression between myogenic stages. We identified 45 739 differentially methylated regions (DMRs) between stages, and the majority (N=34 232) were hypomethylated at 70versus 41 dg. Integration of methylation and transcriptomic data revealed strong associations between differential gene methylation and expression. Differential miRNA methylation was significantly negatively correlated with abundance, and dynamic expression of assayed miRNAs persisted postnatally. Motif analysis revealed significant enrichment of myogenic regulatory factor motifs among hypomethylated regions, suggesting that DNA hypomethylation may function to increase accessibility of muscle-specific transcription factors. We show that developmental DMRs are enriched for GWAS SNPs for muscle- and meat-related traits, demonstrating the potential for epigenetic processes to influence phenotypic diversity. Our results enhance understanding of DNA methylation dynamics of porcine myogenesis and reveal putative cis-regulatory elements governed by epigenetic processes.

The Impact of a Pulsed Light Stream on the Quality and Durability of the Cold-Stored Longissimus Dorsal Muscle of Pigs.

The purpose of this study was to investigate the effect of pulsed light application (exposure to a pulsed light beam (PL) of 400 Hz for a period of 60 s, with an energy dose of 600 mW and wavelengths of 660 and 405 nm) on the physicochemical, technological, and sensory properties, as well as the nutritional value and shelf life of cold-storage pig longissimus dorsi muscle. Each muscle was divided into six parts, three of which were control samples, and the rest were exposed to pulsed light. The detailed laboratory tests of the meat were conducted 1, 7, and 10 days after slaughter. The meat was cold stored at +3 °C ± 0.5 °C. The study showed that the application of pulsed light has a favorable effect on lowering the TBARS index, oxidation-reduction potential, and water activity values. In addition, the application of PL had no statistically significant effect on the variation in the perception of selected sensory characteristics of meat. Furthermore, PL processing, as a low-energy-intensive method that can be environmentally friendly and thus have a large potential for implementation, is an innovative way to extend the shelf life, especially of raw meat, without a negative impact on its quality. This is of particular importance for food security (especially in the quantitative and qualitative aspects of food, but also in terms of food safety).

Identification and Functional Prediction of Long Non-Coding RNA in Longissimus Dorsi Muscle of Queshan Black and Large White Pigs.

Long non-coding RNA (lncRNA) participates in the regulation of various biological processes, but its function and characteristics in intramuscular fat (IMF) deposition in different breeds of pigs have not been fully understood. IMF content is one of the important factors affecting pork quality. In the present study, the differentially expressed lncRNAs (DE lncRNAs) and their target genes were screened by comparing Queshan Black (QS) and Large White (LW) pigs based on RNA-seq. The results displayed 55 DE lncRNAs between QS and LW, 29 upregulated and 26 downregulated, with 172 co-located target genes, and 6203 co-expressed target genes. The results of GO and KEGG analysis showed that the target genes of DE lncRNAs were involved in multiple pathways related to lipogenesis and lipid metabolism, such as the lipid biosynthetic process, protein phosphorylation, activation of MAPK activity, and the Jak-STAT signaling pathway. By constructing regulatory networks, lincRNA-ZFP42-ACTC1, lincRNA-AMY2-STAT1, and/or lincRNA-AMY2/miR-204/STAT1 were sieved, and the results indicate that lncRNA could participate in IMF deposition through direct regulation or ceRNA. These findings provide a basis for analyzing the molecular mechanism of IMF deposition in pigs and lay a foundation for developing and utilizing high-quality resources of local pig breeds.

Identification of Differentially Expressed Genes in the Longissimus Dorsi Muscle of Luchuan and Duroc Pigs by Transcriptome Sequencing.

The Duroc pig originated in the United States and is a typical lean-meat pig. The breed grows fast, and the body size is large, but the meat quality is poor. The Luchuan pig is one of eight excellent local breeds in China; it has tender meat but is small in size. To study the factors that determine growth, we selected the longissimus dorsi muscle of Luchuan and Duroc pigs for transcriptome sequencing. The results of the transcriptome showed that 3682 genes were differentially expressed (DEGs) in the longissimus dorsi muscle of Duroc and Luchuan pigs. We screened out genes related to muscle development and selected the MYL2 (Myosin light chain-2) gene to perform preliminary research. Gene Ontology (GO) enrichment of biological functions and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the gene products were mainly involved in the Akt/FoxO signaling pathway, fatty acid metabolism, arachidonic acid metabolism and glycine, serine and threonine metabolism. Such pathways contributed to skeletal muscle growth, fatty acid metabolism and intramuscular fat deposition. These results provide insight into the mechanisms underlying the formation of skeletal muscle and provide candidate genes to improve growth traits, as well as contribute to improving the growth and development traits of pigs through molecular breeding.

Effects of fermented broccoli stem and leaf residue on growth performance, serum characteristics and meat quality of growing pigs.

The aim of this study was to evaluate the effects of fermented broccoli stem and leaf residue (FBR) on the growth performance, serum biochemical characteristics, and meat quality of growing pigs. A total of 72 growing pigs (Durox × Landrace × Yorkshire) were subjected to three dietary treatments with different levels (0%, 5%and 10%) of FBR with three replicates for an experimental period of 70 day. The average daily feed intake of growing pigs was higher (p < 0.05) in the 5% FBR treatment compared with the control group (0% FBR). The serum urea nitrogen content in growing pigs was lower (p < 0.05) in the 5% and 10% FBR treatments. The lightness value was higher (p < 0.05) in the longissimus dorsi muscle of pigs fed 5% and 10% FBR diets compared with the control group, and the yellowness value was increased in pigs fed the 10% FBR diet compared with pigs fed the control diet. Overall, the beneficial effects of FBR supplementation on serum biochemical parameters, and meat colour without undermining the growth performance indicate that up to 10% FBR could be used in diets to enhance the production of growing pigs.

Effects of low-protein diet and feed restriction on mRNA expression of cationic amino acid transporters in porcine skeletal muscles.

We investigated the effects of a low-protein diet and feed restriction on the mRNA expression of cationic amino acid transporters (CATs) in the longissimus dorsi (LD), rhomboideus (RH), and biceps femoris (BF) muscles of pigs. Eighteen piglets were divided into three groups: a control (CP21%), low-protein diet (LP, CP16%), and feed-restricted diet (FR, CP21%, 76% feed intake of control pigs) groups. The expression levels of CAT-1 in the LD and BF muscles of LP pigs were higher than that of control pigs, whereas that of FR pigs showed no difference. The CAT-2A expression levels in the RH muscle of FR pigs were higher than that of control pigs. The free lysine concentrations in all muscles of LP and FR pigs were lower than that of control pigs. To examine the factors that affect CATs mRNA expression, we evaluated the effects of lysine, arginine, insulin-like growth factor-I, and dexamethasone on the expression of CATs in C2C12 myotubes. CAT-1 expression levels increased in lysine and/or arginine deprivation. We show that CAT-1 and CAT-2A expression levels in skeletal muscles differ in response to dietary treatments and CAT-1 expression in skeletal muscles appears to increase in response to low free lysine concentrations.

Construction and Comprehensive Analysis of miRNAs and Target mRNAs in Longissimus dorsi Muscle of Queshan Black and Large White Pigs.

A miRNA-mRNA combination analysis was performed on the longissimus dorsi muscle of adult Queshan Black and Large White pigs by RNA-seq technology to reveal the molecular mechanism affecting pork quality traits. The sequencing results showed that 39 miRNAs were differentially expressed between Queshan Black and Large White pigs, which targeted 5234 mRNAs, and 15 differentially expressed miRNAs targeted 86 differentially expressed mRNAs. The qRT-PCR results showed that miRNAs showed similar expression patterns to RNA-seq. The GO analysis indicated that differentially expressed miRNAs with differential target mRNAs were primarily involved in biological processes such as phospholipase activity, MAP-kinase scaffold activity, lipase activity, and regulation of the extent of cell growth. The KEGG analysis also revealed that such mRNAs were significantly enriched in the ECM-receptor interaction, sphingolipid metabolism, apoptosis, PI3K-Akt signaling pathway, and AMPK signaling pathway. In addition, software predictions showed that 17 (13 of which were upregulated and four were downregulated) of 39 differentially expressed miRNAs targeted 118 negatively correlated expression mRNAs. The upregulated miRNAs contained 103 negatively correlated target mRNAs, whereas the downregulated miRNAs contained 15 negatively correlated target mRNAs. The GO analysis showed that such mRNAs were primarily involved in MAP-kinase scaffold activity, myoblast development, and peptidyl-lysine methylation, and the KEGG analysis showed significant enrichment in ECM-receptor interaction and focal adhesion. The functional enrichment analysis of miRNA target genes revealed that miR-328 was screened out as a key miRNA, and preliminary functional validation was performed. Moreover, the overexpressed miR-328 could affect the expression of proliferation-related genes, such as CDK2, CDK4, CCNB1, CCND1, CCNE1, and PCNA. These results indicated that miR-328 may regulate fat deposition and affect meat quality by influencing related pathways. This study revealed that the miRNA-mRNA regulatory axis affects fat deposition and skeletal muscle development, which provides a theoretical basis for further study on the molecular mechanism of meat quality.

Identification of Candidate Genes and Regulatory Competitive Endogenous RNA (ceRNA) Networks Underlying Intramuscular Fat Content in Yorkshire Pigs with Extreme Fat Deposition Phenotypes.

Intramuscular fat (IMF) content is vital for pork quality, serving an important role in economic performance in pig industry. Non-coding RNAs, with mRNAs, are involved in IMF deposition; however, their functions and regulatory mechanisms in porcine IMF remain elusive. This study assessed the whole transcriptome expression profiles of the Longissimus dorsi muscle of pigs with high (H) and low (L) IMF content to identify genes implicated in porcine IMF adipogenesis and their regulatory functions. Hundreds of differentially expressed RNAs were found to be involved in fatty acid metabolic processes, lipid metabolism, and fat cell differentiation. Furthermore, combing co-differential expression analyses, we constructed competing endogenous RNAs (ceRNA) regulatory networks, showing crosstalk among 30 lncRNAs and 61 mRNAs through 20 miRNAs, five circRNAs and 11 mRNAs through four miRNAs, and potential IMF deposition-related ceRNA subnetworks. Functional lncRNAs and circRNAs (such as MSTRG.12440.1, ENSSSCT00000066779, novel_circ_011355, novel_circ_011355) were found to act as ceRNAs of important lipid metabolism-related mRNAs (LEP, IP6K1, FFAR4, CEBPA, etc.) by sponging functional miRNAs (such as ssc-miR-196a, ssc-miR-200b, ssc-miR10391, miR486-y). These findings provide potential regulators and molecular regulatory networks that can be utilized for research on IMF traits in pigs, which would aid in marker-assisted selection to improve pork quality.

Comparative Transcriptomic Analysis of mRNAs, miRNAs and lncRNAs in the Longissimus dorsi Muscles between Fat-Type and Lean-Type Pigs.

In pigs, meat quality and production are two important traits affecting the pig industry and human health. Compared to lean-type pigs, fat-type pigs contain higher intramuscular fat (IMF) contents, better taste and nutritional value. To uncover genetic factors controlling differences related to IMF in pig muscle, we performed RNA-seq analysis on the transcriptomes of the Longissimus dorsi (LD) muscle of Laiwu pigs (LW, fat-type pigs) and commercial Duroc × Landrace × Yorkshire pigs (DLY, lean-type pigs) at 150 d to compare the expression profiles of mRNA, miRNA and lncRNA. A total of 225 mRNAs, 12 miRNAs and 57 lncRNAs were found to be differentially expressed at the criteria of |log2(foldchange)| > 1 and q < 0.05. The mRNA expression of LDHB was significantly higher in the LD muscle of LW compared to DLY pigs with log2(foldchange) being 9.66. Using protein interaction prediction method, we identified more interactions of estrogen-related receptor alpha (ESRRA) associated with upregulated mRNAs, whereas versican (VCAN) and proenkephalin (PENK) were associated with downregulated mRNAs in LW pigs. Integrated analysis on differentially expressed (DE) mRNAs and miRNAs in the LD muscle between LW and DLY pigs revealed two network modules: between five upregulated mRNA genes (GALNT15, FKBP5, PPARGC1A, LOC110258214 and LOC110258215) and six downregulated miRNA genes (ssc-let-7a, ssc-miR190-3p, ssc-miR356-5p, ssc-miR573-5p, ssc-miR204-5p and ssc-miR-10383), and between three downregulated DE mRNA genes (IFRD1, LOC110258600 and LOC102158401) and six upregulated DE miRNA genes (ssc-miR1379-3p, ssc-miR1379-5p, ssc-miR397-5p, ssc-miR1358-5p, ssc-miR299-5p and ssc-miR1156-5p) in LW pigs. Based on the mRNA and ncRNA binding site targeting database, we constructed a regulatory network with miRNA as the center and mRNA and lncRNA as the target genes, including GALNT15/ssc-let-7a/LOC100523888, IFRD1/ssc-miR1379-5p/CD99, etc., forming a ceRNA network in the LD muscles that are differentially expressed between LW and DLY pigs. Collectively, these data may provide resources for further investigation of molecular mechanisms underlying differences in meat traits between lean- and fat-type pigs.

Effect of Gardenia Pomace Supplementation on Growth Performance, Blood Metabolites, Immune and Antioxidant Indices, and Meat Quality in Xiangcun Pigs.

Simple SummaryThe present study investigated the effects of gardenia pomace on growth performance, blood metabolites, immune and antioxidant indices, and meat quality in Xiangcun pigs. Gardenia pomace supplementation improved the immunity and antioxidant capacities of the Xiangcun pigs and did not negatively affect the growth performance or meat quality of Xiangcun pigs. Gardenia pomace could potentially be used as an unconventional feedstuff in the diet of finishing pigs.To investigate the effect of gardenia pomace (GP) as an unconventional feed of antioxidants, 180 Xiangcun pigs were randomly divided into 3 groups during the finishing period, with 6 replicates per group and 10 pigs per replicate. During the 47-day feeding period, the pigs were fed either a control diet based on corn and soybean meal (control group), or the control diet added with 50 g/kg or 100 g/kg GP (groups GP5 and GP10, respectively). Feed and water were provided ad libitum. One pig per replicate was slaughtered and sampled. The effects on growth performance, meat quality, digestibility, metabolism, and immunity and antioxidant properties of the pigs were investigated. The results showed that GP had no significant effect on the growth performance of Xiangcun pigs. Compared with the control group, the digestibility of crude ash, phosphorus, and crude fibre of pigs in the GP groups improved (p < 0.01), and the content of inosinic acid in the longissimus dorsi muscle increased (p < 0.05). The addition of GP to the diet significantly increased superoxide dismutase (SOD) levels in the liver and spleen, and glutathione peroxidase (GSH-Px) activity in the longissimus dorsi muscle and spleen (p < 0.05). Additionally, it significantly reduced the contents of malondialdehyde (MDA) in the liver and spleen (p < 0.05). The GP5 group had a higher inosinic acid content in the longissimus dorsi and lower levels of the inflammatory factor interleukin-2 and interleukin-8 than those in the other groups (p < 0.05). The GP10 group had a higher IgA level (p < 0.05). Adding different proportions of GP to the diet improved the a* and b* of the longissimus dorsi muscles of Xiangcun pigs (p < 0.05). In summary, GP, as an unconventional feed, improved the apparent digestibility of the diet and body antioxidant capacity in Xiangcun pigs during the finishing period and did not negatively affect the growth performance or meat quality.