Intramuscular fat content in meat-producing animals: development, genetic and nutritional control, and identification of putative markers

A review of emerging technologies, nutritional practices, and management strategies to improve intramuscular fat composition in beef cattle

The flavour, tenderness and juiciness of the beef are all impacted by the composition of the intramuscular fat (IMF), which is a key determinant of beef quality. Thus, enhancing the IMF composition of beef cattle has become a major area of research. Consequently, the aim of this paper was to provide insight and synthesis into the emerging technologies, nutritional practices and management strategies to improve IMF composition in beef cattle. This review paper examined the current knowledge of management techniques and nutritional approaches relevant to cattle farming in the beef industry. It includes a thorough investigation of animal handling, weaning age, castration, breed selection, sex determination, environmental factors, grazing methods, slaughter weight and age. Additionally, it rigorously explored dietary energy levels and optimization of fatty acid profiles, as well as the use of feed additives and hormone implant techniques with their associated regulations. The paper also delved into emerging technologies that are shaping future beef production, such as genomic selection methods, genome editing techniques, epigenomic analyses, microbiome manipulation strategies, transcriptomic profiling approaches and metabolomics analyses. In conclusion, a holistic approach combining genomic, nutritional and management strategies is imperative for achieving targeted IMF content and ensuring high-quality beef production.

Transcriptome analysis reveals the effects of Schizochytrium sp. on the meat quality attributes of Tan lambs

Schizochytrium sp., a feed additive, positively affects the quality of animal meat. In this study, the molecular mechanisms through which dietary Schizochytrium sp. affects the meat quality characteristics of Tan lambs were investigated using transcriptomic techniques. The findings demonstrate that the lambs supplemented with Schizochytrium sp. had a larger loin eye area and a higher average daily gain and intramuscular fat content (P < 0.05). They also had lower drip loss (at 24 and 48 h) and shear force (P < 0.05). Further, 745 genes were differentially expressed between lambs supplemented with Schizochytrium and the control group. Moreover, KEGG pathway analysis showed that the ECM-receptor interaction pathway, which is related to muscle generation and intramuscular fat deposition, was significantly enriched in the lambs administered a diet containing Schizochytrium sp. Herein, we identified some pivotal genes linked to muscular system development and lipid metabolism. Thus, using Schizochytrium sp. may boost the meat quality of Tan lambs by modifying the expression of genes related to hub pathways. The results supply a new basis to determine the molecular mechanisms through which Schizochytrium sp. supplementation regulates the meat quality characteristics of sheep.

Relationships between European carcass evaluation and Meat Standards Australia grading scheme applied to young beef cattle

The European carcass grading scheme (EUROP) places large emphasis on meat yield and therefore on quantitative traits such as carcass conformation and superficial fat coverage. However, it falls short in considering sensory properties and consumer satisfaction. In contrast, the Meat Standards Australia (MSA) grading scheme considers, among others, animals' ossification, marbling, and ultimate pH as primary indicators of beef eating quality. This study aims to characterize MSA carcass grading scheme applied to the Italian beef production system, considering its significant role in European beef market. The study involved 3204 Charolais, Limousin, and crossbred young bulls and heifers slaughtered in a commercial Italian abattoir. Data collection spanned a broad range of variables, including animal characteristics, MSA traits, and EUROP carcass grading traits. Regardless of the sex of the animal, no significant relationship was observed between MSA traits and EUROP carcass grading scores. Factors such as sex, age, and arrival season at the fattening unit significantly affected most of MSA traits. Females had significantly higher marbling score, and lower ossification score and hump height than males. Animals imported in autumn and winter had significantly lower marbling score, but similar ossification score compared to those imported in spring and summer. Older females had the highest marbling scores. While further research is needed to assess whether the MSA grading scheme can be adapted to all different European rearing systems, results of this study are a prelude to the potential benefits that the MSA grading scheme can bring to the European beef industry.

Transcriptome-metabolome reveals the molecular changes in meat production and quality in the hybrid populations of Sichuan white goose

Hybrid breeding has proven to enhance meat quality and is extensively utilized in goose breeding. Nevertheless, there is a paucity of research investigating the molecular mechanisms that underlie the meat quality of hybrid geese. In this study, we employed the Sichuan White Goose as the maternal line for hybridization with the Zhedong White Goose and Tianfu Meat Goose P3 line. We assessed the growth and slaughter meat quality performance of 10-wk-old hybrid offspring in comparison to Sichuan white goose purebred offspring. The results indicate that hybrid geese have significantly improved performance in growth and slaughter meat quality. Furthermore, we conducted a comprehensive analysis of the chest muscles of hybrid offspring through transcriptomics and metabolomics to unravel the effects of hybrid breeding on growth and meat quality. A total of 673 differentially expressed genes (DEGs), and 93 differentially expressed metabolites were identified. The joint analysis highlighted the significant enrichment of DEGs AMPD1, AMPD3, RRM2, ENTPD3, and the metabolite UMP in the nucleotide metabolism pathway. These findings underscore the crucial role of these genetic and metabolic factors in regulating muscle growth and meat quality in hybrid populations.

Activation of skeletal carbohydrate-response element binding protein (ChREBP)-mediated de novo lipogenesis increases intramuscular fat content in chickens

The intracellular lipids in muscle cells of farm animals play a crucial role in determining the overall intramuscular fat (IMF) content, which has a positive impact on meat quality. However, the mechanisms underlying the deposition of lipids in muscle cells of farm animals are not yet fully understood. The purpose of this study was to determine the roles of carbohydrate-response element binding protein (ChREBP) and fructose in IMF deposition of chickens. For virus-mediated ChREBP overexpression in tibialis anterior (TA) muscle of chickens, seven 5-d-old male yellow-feather chickens were used. At 10 d after virus injection, the chickens were slaughtered to obtain TA muscles for analysis. For fructose administration trial, sixty 9-wk-old male yellow-feather chickens were randomly divided into 2 groups, with 6 replicates per group and 5 chickens per replicate. The chickens were fed either a basal diet or a basal diet supplemented with 10% fructose (purity ≥ 99%). At 4 wk later, the chickens were slaughtered, and breast and thigh muscles were collected for analysis. The results showed that the skeletal ChREBP mRNA levels were positively associated with IMF content in multiple species, including the chickens, pigs, and mice (P < 0.05). ChREBP overexpression increased lipid accumulation in both muscle cells in vitro and the TA muscles of mice and chickens in vivo (P < 0.05), by activation of the de novo lipogenesis (DNL) pathway. Moreover, activation of ChREBP by dietary fructose administration also resulted in increased IMF content in mice and notably chickens (P < 0.05). Furthermore, the lipidomics analysis revealed that ChREBP activation altered the lipid composition of chicken IMF and tented to improve the flavor profile of the meat. In conclusion, this study found that ChREBP plays a pivotal role in mediating the deposition of fat in chicken muscles in response to fructose-rich diets, which provides a novel strategy for improving meat quality in the livestock industry.

Evaluation of carcass traits, meat quality and the expression of lipid metabolism-related genes in different slaughter ages and muscles of Taihang black goats

OBJECTIVE

This study was conducted to investigate the effect of slaughter age on carcass traits, meat quality, and the relative mRNA levels of lipid metabolism-related genes in different muscles of Taihang black goats.

METHODS

In this study, the triceps brachii (TB), longissimus dorsi (LD) and gluteus (GL) muscles of 15 grazing Taihang black goats slaughtered at the age of 2, 3, and 4 (designated as 2-year-old, 3-year-old, and 4-year-old, respectively) were collected. The differences in carcass shape, meat quality, amino acid composition and lipid metabolism gene expression among Taihang black goats of different ages and from different plant parts were compared.

RESULTS

Compared with goats at other ages, goats slaughtered at the age of 4 had greater live and carcass weights, meat weights, bone weights and skin areas (p<0.05). LD in the 4-years-old had the lowest cooking loss and moisture content. The crude protein content in the LD of 2-year-old was significantly greater than that in the other age group, and at the age of 2, the LD had the highest crude protein content than TB and GL. The highest fat content was in LD, followed by TB, for goats slaughtered at the age of 4. Eight out of 9 essential amino acids had higher content in the TB compared with other muscles, regardless of age. The total essential amino acid content was highest in the 4-year-old and lowest in the GL muscle at the age of 3. The sterol regulatory element-binding protein-1c (SREBP-1c) and adipose triglyceride lipase (ATGL) genes were significantly more abundant in the TB muscle than in the other muscles for goats slaughtered at the age of 2. At the age of 4, the ATGL and peroxisome proliferator-activated receptor γ (PPARγ) genes were significantly more abundant in the GL than in the LD, while the fatty acid synthase (FAS) genes were significantly less abundant in the GL than in the other muscles. Similarly, compared with those in goats of other ages, the relative mRNA expression levels of the FAS and heart-type fatty acid binding protein (H-FABP) genes in goats slaughtered at the age of 4 were the highest, and the relative mRNA expression of the PPARγ gene was the lowest (p<0.05). The relative mRNA expression of the H-FABP and FAS genes was positively correlated with the intramuscular fat (IMF) content, while the relative mRNA expression levels of the PPARγ and ATGL genes was negatively correlated with the IMF content.

CONCLUSION

Overall, a better nutritional value was obtained for TB from 4-year-old goats, in which the total essential amino acid and fat contents were greater than those of other muscles. The comprehensive action of lipid metabolism genes was consistent with that of the IMF content, among which the FAS, H-FABP, PPARγ, and ATGL genes had positive and negative effects on the process of IMF deposition in Taihang black goats.

LEP inhibits intramuscular adipogenesis through the AMPK signaling pathway in vitro

Leptin can indirectly regulate fatty-acid metabolism and synthesis in muscle in vivo and directly in incubated muscle ex vivo. In addition, non-synonymous mutations in the bovine leptin gene (LEP) are associated with carcass intramuscular fat (IMF) content. However, the effects of LEP on lipid synthesis of adipocytes have not been clearly studied at the cellular level. Therefore, this study focused on bovine primary intramuscular preadipocytes to investigate the effects of LEP on the proliferation and differentiation of intramuscular preadipocytes, as well as its regulatory mechanism in lipid synthesis. The results showed that both the LEP and leptin receptor gene (LEPR) were highly expressed in IMF tissues, and their mRNA expression levels were positively correlated at different developmental stages of intramuscular preadipocytes. The overexpression of LEP inhibited the proliferation and differentiation of intramuscular preadipocytes, while interference with LEP had the opposite effect. Additionally, LEP significantly promoted the phosphorylation level of AMPKα by promoting the protein expression of CAMKK2. Meanwhile, rescue experiments showed that the increasing effect of AMPK inhibitors on the number of intramuscular preadipocytes was significantly weakened by the overexpression of LEP. Furthermore, the overexpression of LEP could weaken the promoting effect of AMPK inhibitor on triglyceride content and droplet accumulation, and prevent the upregulation of adipogenic protein expression (SREBF1, FABP4, FASN, and ACCα) caused by AMPK inhibitor. Taken together, LEP acted on the AMPK signaling pathway by regulating the protein expression of CAMKK2, thereby downregulating the expression of proliferation-related and adipogenic-related genes and proteins, ultimately reducing intramuscular adipogenesis.

Unraveling the flavor profiles of chicken meat: Classes, biosynthesis, influencing factors in flavor development, and sensory evaluation

Chicken is renowned as the most affordable meat option, prized by consumers worldwide for its unique flavor, and universally recognized for its essential savory flavor. Current research endeavors are increasingly dedicated to exploring the flavor profile of chicken meat. However, there is a noticeable gap in comprehensive reviews dedicated specifically to the flavor quality of chicken meat, although existing reviews cover meat flavor profiles of various animal species. This review aims to fill this gap by synthesizing knowledge from published literature to describe the compounds, chemistry reaction, influencing factors, and sensory evaluation associated with chicken meat flavor. The flavor compounds in chicken meat mainly included water-soluble low-molecular-weight substances and lipids, as well as volatile compounds such as aldehydes, ketones, alcohols, acids, esters, hydrocarbons, furans, nitrogen, and sulfur-containing compounds. The significant synthesis pathways of flavor components were Maillard reaction, Strecker degradation, lipid oxidation, lipid-Maillard interaction, and thiamine degradation. Preslaughter factors, including age, breed/strain, rearing management, muscle type, and sex of chicken, as well as postmortem conditions such as aging, cooking conditions, and low-temperature storage, were closely linked to flavor development and accounted for the significant differences observed in flavor components. Moreover, the sensory methods used to evaluate the chicken meat flavor were elaborated. This review contributes to a more comprehensive understanding of the flavor profile of chicken meat. It can serve as a guide for enhancing chicken meat flavor quality and provide a foundation for developing customized chicken products.

Single-nucleus RNA sequencing and lipidomics reveal characteristics of transcriptional and lipid composition in porcine longissimus dorsi muscle

BACKGROUND

Global per capita meat consumption continues to rise, especially pork. Meat quality is influenced by the content of intramuscular fat (IMF) as a key factor. The longissimus dorsi muscle of Dahe pigs (DHM, IMF: 7.98% ± 1.96%) and Dahe black pigs (DHBM, IMF: 3.30% ± 0.64%) was studied to explore cellular heterogeneity and differentially expressed genes (DEGs) associated with IMF deposition using single-nucleus RNA sequencing (snRNA-seq). The lipid composition was then analyzed using non-targeted lipidomics.

RESULTS

A total of seven cell subpopulations were identified, including myocytes, fibroblast/fibro/adipogenic progenitors (FAPs), satellite cells, endothelial cells, macrophages, pericytes, and adipocytes. Among them, FAPs and adipocytes were more focused because they could be associated with lipid deposition. 1623 DEGs in the FAPs subpopulation of DHBM were up-regulated compared with DHM, while 1535 were down-regulated. These DEGs enriched in the glycolysis/gluconeogenesis pathway. 109 DEGs were up-regulated and 806 were down-regulated in the adipocyte subpopulation of DHBM compared with DHM, which were mainly enriched in the PPAR signaling pathway and fatty acid (FA) biosynthesis. The expression level of PPARG, ABP4, LEP, and ACSL1 genes in DHM was higher than that in DHBM. Lipidomics reveals porcine lipid composition characteristics of muscle tissue. A total of 41 lipid classes and 2699 lipid species were identified in DHM and DHBM groups. The top ten relative peak areas of lipid classes in DHM and DHBM were triglyceride (TG), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), diglyceride (DG), cardiolipin (CL), ceramides (Cer), Simple Glc series (Hex1Cer), sphingomyelin (phSM), and phosphatidylinositol (PI). The relative peak areas of 35 lipid species in DHM were lower than DHBM, and 28 lipid species that were higher. There was a significant increase in the TG fatty acyl chains C6:0, C17:0, and C11:4, and a significant decrease in C16:0, C18:1, C18:2, and C22:4 in DHBM (p < 0.05).

CONCLUSIONS

C16:0 FA may downregulate the expression level of PPARG gene, which leads to the downregulation of fat metabolism-related genes such as ACSL, PLIN2, and FABP4 in DHBM compared with DHM. This may be the reason that the lipid deposition ability of Dahe pigs is stronger than that of Dahe black pigs, which need further investigation.

Polymorphisms of the SCD1 Gene and Its Association Analysis with Carcass, Meat Quality, Adipogenic Traits, Fatty Acid Composition, and Milk Production Traits in Cattle

Stearoyl-CoA desaturase-1 (SCD1) is a key enzyme in the biosynthesis of monounsaturated fatty acids and is considered a candidate gene for improving milk and meat quality traits. Sanger sequencing was employed to investigate the genetic polymorphism of the fifth exon and intron of bovine SCD1, revealing four SNPs, g.21272246 A>G, g.21272306 T>C, g.21272422 C>T, and g.21272529 A>G. Further variance analysis and multiple comparisons were conducted to examine the relationship between variation sites and economic traits in Chinese Simmental cattle, as well as milk production traits in Holstein cows. The findings revealed these four loci exhibited significant associations with carcass traits (carcass weight, carcass length, backfat thickness, and waist meat thickness), meat quality (pH value, rib eye area, and marbling score), adipogenic traits (fat score and carcass fat coverage rate), and fatty acid composition (linoleic acid and α-linolenic acid). Furthermore, these loci were additionally found to be significantly associated with average milk yield and milk fat content in cows. In addition, a haplotype analysis of combinations of SNPs showed that H2H3 has a significant association with adipogenic traits and H2H2 was associated with higher levels of linoleic acid and α-linolenic acid than the other combinations. These results suggest that the four SNPs are expected to be prospective genetic markers for the above economic traits. In addition, the function of SNPs in exon 5 of SCD1 on gene expression and protein structure needs to be explored in the future.

Unraveling the Genetic Foundations of Broiler Meat Quality: Advancements in Research and Their Impact

As societal progress elevates living standards, the focus on meat consumption has shifted from quantity to quality. In broiler production, optimizing meat quality has become paramount, prompting efforts to refine various meat attributes. Recent advancements in sequencing technologies have revealed the genome's complexity, surpassing previous conceptions. Through experimentation, numerous genetic elements have been linked to crucial meat quality traits in broiler chickens. This review synthesizes the current understanding of genetic determinants associated with meat quality attributes in broilers. Researchers have unveiled the pivotal insights detailed herein by employing diverse genomic methodologies such as QTL-based investigations, candidate gene studies, single-nucleotide polymorphism screening, genome-wide association studies, and RNA sequencing. These studies have identified numerous genes involved in broiler meat quality traits, including meat lightness (COL1A2 and ACAA2), meat yellowness (BCMO1 and GDPD5), fiber diameter (myostatin and LncIRS1), meat pH (PRDX4), tenderness (CAPN1), and intramuscular fat content (miR-24-3p and ANXA6). Consequently, a comprehensive exploration of these genetic elements is imperative to devise novel molecular markers and potential targets, promising to revolutionize strategies for enhancing broiler meat quality.

Preliminary genetic parameter estimates of meat quality traits in Hu sheep

Because substantial numbers of Chinese consumers are prepared to pay for tender and quality lamb, meat quality traits are becoming more relevant for breeding programs for Chinese sheep breeds. The current study estimated heritabilities and genetic correlations for 13 meat quality traits recorded on lamb loins from Hu sheep. Heritability estimates ranged from 0.04 ± 0.06 for meat redness at 45 min to 0.57 ± 0.10 for drip loss, with most of the meat quality traits having moderate heritabilities. Positive genetic correlations were observed among meat color traits. Intramuscular fat (IMF) was genetically correlated with most meat quality traits, indicating that increasing IMF can favor meat pH, color, and tenderness, but would lead to increased cooking loss. Direct selection to increase IMF of loins is recommended to be included in breeding programs for Hu sheep, as it was more efficient than indirect selection on the other meat quality traits. The genetic parameters presented in this preliminary study provide valuable genetic information needed to design a breeding program aimed at improving the quality of lamb meat from Hu sheep.

Fat deposition and partitioning for meat production in cattle and sheep

In markets for beef and sheep meat, an appropriate level of intramuscular fat (IMF) is highly desirable for meat-eating quality, but strategies to improve it usually lead to an undesirable excess in carcase fat, presenting a major challenge to livestock producers. To solve this problem, we need to understand the partitioning of fat among the major fat depots: IMF, subcutaneous fat (SCF) and visceral fat (VF). In most genotypes of cattle and sheep, the rate of accretion is lower for IMF than for SCF and VF, so genetic selection for a high level of IMF, or the use of an increased dietary energy supply to promote IMF deposition, will increase overall fatness and feed costs. On the other hand, feeding postnatal calves with excessive concentrates promotes IMF deposition, so a nutritional strategy is feasible. With genetic strategies, several problems arise: 1) positive genetic correlations between IMF, SCF and VF differ among genotypes in both cattle and sheep; 2) genotypes appear to have specific, characteristic rates of accretion of IMF during periods of growth and fattening; 3) most breeds of cattle and sheep naturally produce meat with relatively low levels of IMF, but IMF does vary substantially among individuals and breeds so progress is possible through accurate measurement of IMF. Therefore, an essential prerequisite for selection will be knowledge of the genetic correlations and fat accretion rates for each genotype. Currently, selection for IMF is based on existing technology that directly measures IMF in the progeny or siblings, or estimates IMF in live animals. New technology is needed to permit the simultaneous measurement of SCF and IMF in the field, thus opening up the possibility of accurate selection, particularly for fat partitioning in live animals. Specifically, there would be great value in detecting individuals with an IMF advantage at an early age so the generation interval could be shortened and genetic gain accelerated. Genetic gain would also be greatly aided if we could select for genes that control adipogenesis and lipogenesis and are also differentially expressed in the various depots.

Identification of potential tissue-specific biomarkers involved in pig fat deposition through integrated bioinformatics analysis and machine learning

Backfat thickness (BT) and intramuscular fat (IMF) content are closely appertained to meat production and quality in pig production. Deposition in subcutaneous adipose (SA) and IMF concerns different genes and regulatory mechanisms. And larger studies with rigorous design should be carried to explore the molecular regulation of fat deposition in different tissues. The purpose of this study is to gain a better understanding of the molecular mechanisms underlying differences in fat deposition among different tissues and identify tissue-specific genes involved in regulating fat deposition. The SA-associated datasets (GSE122349 and GSE145956) and IMF-associated datasets (GSE165613 and GSE207279) were downloaded from the Gene Expression Omnibus (GEO) as the BT and IMF group, respectively. Subsequently, the Robust Rank Aggregation (RRA) algorithm identified 27 down- and 29 up-regulated differentially expressed genes (DEGs) in the BT group. Based on bioinformatics and three machine learning algorithms, four SA deposition-related potential biomarkers, namely ACLY, FASN, ME1, and ARVCF were selected. FASN was evaluated as the most valuable biomarker for the SA mechanism. The 18 down- and 34 up-regulated DEGs in the IMF group were identified, and ACTA2 and HMGCL were screened as the IMF deposition-related candidate core genes, especially the ACTA2 may play the critical role in IMF deposition regulation. Moreover, based on the constructed ceRNA network, we postulated that the role of predicted ceRNA interaction network of XIST, NEAT1/miR-15a-5p, miR-16-5p, miR-424-5p, miR-497-5p/FASN were vital in the SA metabolism, XIST, NEAT1/miR-27a/b-3p, 181a/c-5p/ACTA2 might contribute to the regulation to IMF metabolism, which all gave suggestions in molecular mechanism for regulation of fat deposition. These findings may facilitate advancements in porcine quality at the genetic and molecular levels and assist with human obesity-associated diseases.

A review of the role of epigenetic studies for intramuscular fat deposition in beef cattle

Intramuscular fat (IMF) deposition profoundly influences meat quality and economic value in beef cattle production. Meanwhile, contemporary developments in epigenetics have opened new outlooks for understanding the molecular basics of IMF regulation, and it has become a key area of research for world scholars. Therefore, the aim of this paper was to provide insight and synthesis into the intricate relationship between epigenetic mechanisms and IMF deposition in beef cattle. The methodology involves a thorough analysis of existing literature, including pertinent books, academic journals, and online resources, to provide a comprehensive overview of the role of epigenetic studies in IMF deposition in beef cattle. This review summarizes the contemporary studies in epigenetic mechanisms in IMF regulation, high-resolution epigenomic mapping, single-cell epigenomics, multi-omics integration, epigenome editing approaches, longitudinal studies in cattle growth, environmental epigenetics, machine learning in epigenetics, ethical and regulatory considerations, and translation to industry practices from perspectives of IMF deposition in beef cattle. Moreover, this paper highlights DNA methylation, histone modifications, acetylation, phosphorylation, ubiquitylation, non-coding RNAs, DNA hydroxymethylation, epigenetic readers, writers, and erasers, chromatin immunoprecipitation followed by sequencing, whole genome bisulfite sequencing, epigenome-wide association studies, and their profound impact on the expression of crucial genes governing adipogenesis and lipid metabolism. Nutrition and stress also have significant influences on epigenetic modifications and IMF deposition. The key findings underscore the pivotal role of epigenetic studies in understanding and enhancing IMF deposition in beef cattle, with implications for precision livestock farming and ethical livestock management. In conclusion, this review highlights the crucial significance of epigenetic pathways and environmental factors in affecting IMF deposition in beef cattle, providing insightful information for improving the economics and meat quality of cattle production.

Proteome Analysis Related to Unsaturated Fatty Acid Synthesis by Interfering with Bovine Adipocyte ACSL1 Gene

Unsaturated fatty acids (UFAs) in beef play a vital role in promoting human health. Long-chain fatty acyl-CoA synthase 1 (ACSL1) is a crucial gene for UFA synthesis in bovine adipocytes. To investigate the protein expression profile during UFA synthesis, we performed a proteomic analysis of bovine adipocytes by RNA interference and non-interference with ACSL1 using label-free techniques. A total of 3558 proteins were identified in both the NC and si-treated groups, of which 1428 were differentially expressed proteins (DEPs; fold change ≥ 1.2 or ≤ 0.83 and p-value < 0.05). The enrichment analysis of the DEPs revealed signaling pathways related to UFA synthesis or metabolism, including cAMP, oxytocin, fatty acid degradation, glycerol metabolism, insulin, and the regulation of lipolysis in adipocytes (p-value < 0.05). Furthermore, based on the enrichment analysis of the DEPs, we screened 50 DEPs that potentially influence the synthesis of UFAs and constructed an interaction network. Moreover, by integrating our previously published transcriptome data, this study established a regulatory network involving differentially expressed long non-coding RNAs (DELs), highlighting 21 DEPs and 13 DELs as key genes involved in UFA synthesis. These findings present potential candidate genes for further investigation into the molecular mechanisms underlying UFA synthesis in bovines, thereby offering insights to enhance the quality of beef and contribute to consumer health in future studies.

CircMEF2C(2, 3) modulates proliferation and adipogenesis of porcine intramuscular preadipocytes by miR-383/671-3p/MEF2C axis

Circular RNA is a special category of non-coding RNA that has emerged as epigenetic regulator of adipose tissue development. However, the mechanism governing intramuscular adipogenesis of circRNA remains largely uncharted. In this study, circMEF2C(2, 3), looped by MEF2C exons 2 and 3, was identified from the pig MEF2C gene. Expression of circMEF2C(2, 3) is upregulated in early stage of intramuscular adipogenesis and muscular tissue of lean pigs (DLY pig). Subsequently, overexpression or knockdown of circMEF2C(2, 3) reflected that it participates in promoting proliferation and inhibiting adipogenic differentiation in porcine intramuscular preadipocytes and murine C3H10T1/2 cells. Mechanically, circMEF2C(2, 3) competitively combined with miR-383 and miR-671-3p to the 3'-UTR of MEF2C, which maintains MEF2C expression in regulating proliferation and adipogenesis. In summary, circMEF2C(2, 3) is a key regulator in the proliferation and adipogenic differentiation of intramuscular adipogenesis, suggesting its potential as a multi-target strategy for adipose development and associated diseases.

A review of the role of transcription factors in regulating adipogenesis and lipogenesis in beef cattle

In the past few decades, genomic selection and other refined strategies have been used to increase the growth rate and lean meat production of beef cattle. Nevertheless, the fast growth rates of cattle breeds are often accompanied by a reduction in intramuscular fat (IMF) deposition, impairing meat quality. Transcription factors play vital roles in regulating adipogenesis and lipogenesis in beef cattle. Meanwhile, understanding the role of transcription factors in regulating adipogenesis and lipogenesis in beef cattle has gained significant attention to increase IMF deposition and meat quality. Therefore, the aim of this paper was to provide a comprehensive summary and valuable insight into the complex role of transcription factors in adipogenesis and lipogenesis in beef cattle. This review summarizes the contemporary studies in transcription factors in adipogenesis and lipogenesis, genome-wide analysis of transcription factors, epigenetic regulation of transcription factors, nutritional regulation of transcription factors, metabolic signalling pathways, functional genomics methods, transcriptomic profiling of adipose tissues, transcription factors and meat quality and comparative genomics with other livestock species. In conclusion, transcription factors play a crucial role in promoting adipocyte development and fatty acid biosynthesis in beef cattle. They control adipose tissue formation and metabolism, thereby improving meat quality and maintaining metabolic balance. Understanding the processes by which these transcription factors regulate adipose tissue deposition and lipid metabolism will simplify the development of marbling or IMF composition in beef cattle.

The myokine CCL5 recruits subcutaneous preadipocytes and promotes intramuscular fat deposition in obese mice

Intramuscular fat (IMF) refers to the lipid stored in skeletal muscle tissue. The number and size of intramuscular adipocytes are the primary factors that regulate IMF content. Intramuscular adipocytes can be derived from either in situ or ectopic migration. In this study, it was discovered that the regulation of IMF levels is achieved through the chemokine (C-C motif) ligand 5 (CCL5)/chemokine (C-C motif) receptor 5 (CCR5) pathway by modulating adipocyte migration. In coculture experiments, C2C12 myotubes were more effective in promoting the migration of 3T3-L1 preadipocytes than C2C12 myoblasts, along with increasing CCL5. Correspondingly, overexpressing the CCR5, one of the receptors of CCL5, in 3T3-L1 preadipocytes facilitated their migration. Conversely, the application of the CCL5/CCR5 inhibitor, MARAVIROC (MVC), reduced this migration. In vivo, transplanted experiments of subcutaneous adipose tissue (SCAT) from transgenic mice expressing green fluorescent protein (GFP) provided evidence that injecting recombinant CCL5 (rCCL5) into skeletal muscle promotes the migration of subcutaneous adipocytes to the skeletal muscle. The level of CCL5 in skeletal muscle increased with obesity. Blocking the CCL5/CCR5 axis by MVC inhibited IMF deposition, whereas elevated skeletal muscle CCL5 promoted IMF deposition in obese mice. These results establish a link between the IMF and the CCL5/CCR5 pathway, which could have a potential application for modulating IMF through adipocyte migration.NEW & NOTEWORTHY C2C12 myotubes attract 3T3-L1 preadipocyte migration regulated by the chemokine (C-C motif) ligand 5 (CCL5)/ chemokine (C-C motif) receptor 5 (CCR5) axis. High levels of skeletal muscle-specific CCL5 promote the migration of subcutaneous adipocytes to skeletal muscle and induce the intramuscular fat (IMF) content.

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. SIGNIFICANCE: The 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.

Association study between SNP markers located in meat quality candidate genes with intramuscular fat content in an endangered dual-purpose cattle population

The aim of this study was to associate single nucleotide polymorphisms (SNP) of the bovine calcium-activated neutral protease µ-calpain, calpastatin, diacylglycerol-O-acyltransferase, adipose fatty acid binding protein, retinoic acid receptor-related orphan receptor C (RORC), and thyroglobulin (TG) gene with intramuscular fat content (IMF). Therefore, 542 animals of the cattle breed "Rotes Höhenvieh" (RHV) were phenotyped for IMF. Genotyping of the animals was performed using polymerase chain reaction-restriction fragment length polymorphism tests for six SNP from candidate genes for meat quality traits. In addition, we calculated allele substitution and dominance effects on IMF. A subgroup of animals (n = 44, reduced dataset) with extraordinary high IMF was analyzed separately. The mean IMF content was 2.5% (SD: 2.8) but ranged from 0.02% to 23.9%, underlining the breeds' potential for quality meat production. Allele and genotype frequencies for all SNP were similar in the complete and reduced dataset. Association analyses in the complete dataset revealed the strongest effects of RORC on IMF (P = 0.075). The log-transformed least-squares mean for IMF of genotype g.3290GG was 0.45 ± 0.16, 0.26 ± 0.14 for genotype g.3290GT, and 0.32 ± 0.14 for genotype g.3290TT. In the reduced dataset, we found a significant effect (P < 0.05) of the g.422C>T-SNP of TG on IMF, with highest IMF for genotype CT (0.91 ± 0.17), lowest IMF for genotype TT (0.37 ± 0.25), and medium IMF for genotype CC (0.59 ± 0.16; log-transformed values). Compared to the complete dataset, allele substitution effects increased in the reduced dataset for most of the SNP, possibly due to the selective genotyping strategy, with focus on animals with highest IMF implying strong phenotypic IMF contrast. Dominance effects were small in both datasets, related to the high heritability of IMF. Results indicated RHV breed particularities regarding the effects of meat quality genes on IMF. An explanation might be the breeding history of RHV with focus on adaptation and resilience in harsh outdoor systems. Consequently, it is imperative to develop breed-specific selection strategies. Allele substitution and dominance effects were in a similar direction in both datasets, suggesting the same breeding approaches for different RHV strains in different regions. Nevertheless, a selective genotyping approach (reduced dataset), contributed to more pronounced genotype effect differences on IMF and dominance values.

Metabolomic, lipidomic, and proteomic profiles provide insights on meat quality differences between Shitou and Wuzong geese

A comprehensive comparison of metabolomic, lipidomic, and proteomic profiles was conducted between the breast and leg muscles of Shitou goose (STE) and Wuzhong goose (WZE), which exhibit significant variations in body size and growth rate, to evaluate their impact on meat quality. WZE had higher intramuscular fat content in their breast muscles, which were also chewier and had higher drip and cooking losses than STE. Metabolomic analysis revealed differential regulation of amino acid and purine metabolism between WZE and STE. Lipidomic analysis indicated a higher abundance of PE and PC lipid molecules in WZE. Integration of proteomic and metabolomic data highlighted purine metabolism and amino acid biosynthesis as the major distinguishing pathways between STE and WZE. The primary differential pathways between breast and leg muscles were associated with energy metabolism and fatty acid metabolism. This comprehensive analysis provides valuable insights into the distinct meat quality of STE and WZE.

Comparative transcriptome analysis of longissimus dorsi muscle reveal potential genes affecting meat trait in Chinese indigenous Xiang pig

In this study, we compared the transcriptome of longissimus dorsi muscle between Guizhou Xiang pigs (XP) and Western commercial Large White pigs (LW), which show diffirent meat quality between them. In terms of meat quality traits, the pH 45 min, color score, backfat thickness, and intramuscular fat (IMF) content were higher in Xiang pigs than in Large White pigs (P < 0.01), while the drip loss, lean meat percentage, shear force, and longissimus dorsi muscle area of Xiang pigs were lower than that of Large White pigs (P < 0.01). Nutrients such as monounsaturated fatty acid (MUFA), total amino acids (TAA), delicious amino acids (DAA) and essential amino acids (EAA) in Xiang pigs were higher than that in Large White pigs, and the proportion of polyunsaturated fatty acid (PUFA) of Xiang pigs was significantly lower than Large White pigs (P < 0.01). Transcriptome analysis identified 163 up-regulated genes and 88 genes down-regulated in Xiang pigs longissimus dorsi muscle. Combined with the correlation analysis and quantitative trait locis (QTLs) affecting meat quality, a total of 227 DEGs were screened to be significantly associated with meat quality values. Enrichment analysis indicated that numerous members of genes were gathered in muscle development, adipogenesis, amino acid metabolism, fatty acid metabolism and synthesis. Of those, 29 genes were identified to be hub genes that might be related with the meat quality of Xiang pig, such as MYOD1, ACTB, ASNS, FOXO1, ARG2, SLC2A4, PLIN2, and SCD. Thus, we screened and identified the potential functional genes for the formation of meat quality in Xiang pigs, which provides a corresponding theoretical basis for the study of the molecular regulatory mechanism of pork quality and the improvement of pork quality.

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-consuming and 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.

Effects of sex on meat quality traits, amino acid and fatty acid compositions, and plasma metabolome profiles in White King squabs

The objective of this study was to investigate the effects of sex on meat quality and the composition of amino and fatty acids in the breast muscles of White King pigeon squabs. Untargeted metabolomics was also conducted to distinguish the metabolic composition of plasma in different sexes. Compared with male squabs, female squabs had greater intramuscular fat (IMF) deposition and lower myofiber diameter and hydroxyproline content, leading to a lower shear force. Female squabs also had higher monounsaturated fatty acid and lower n-6 and n-3 polyunsaturated fatty acid proportions in the breast muscle, and had greater lipogenesis capacity via upregulation of PPARγ, FAS and LPL gene expression. Moreover, female squabs had lower inosine 5'-monophosphate, essential, free and sweet-tasting amino acid contents. Furthermore, Spearman's correlations between the differential plasma metabolites and key meat parameters were assessed, and putrescine, N-acetylglutamic acid, phophatidylcholine (18:0/P-16:0) and trimethylamine N-oxide were found to contribute to meat quality. In summary, the breast meat of male squabs may have better nutritional value than that of females, but it may inferior in terms of sensory properties, which can be attributed to the lower IMF content and higher shear force value. Our findings enhance our understanding of sex variation in squab meat quality, providing a basis for future research on pigeon breeding.

Integrated analysis of differently expressed microRNAs and mRNAs at different postnatal stages reveals intramuscular fat deposition regulation in goats (Capra hircus)

Intramuscular fat refers to the adipose tissue distributed in the muscle. It is an important indicator that affects the quality of goat meat, and can directly affect the tenderness and flavor of goat meat. Our previous study revealed the mRNA that may be crucial for intramuscular fat deposition during goat growth; however, how the microRNAs (miRNAs) are involved in the process is largely unclear. In the present study, a total of 401 known miRNAs and 120 goat novel miRNAs, including 110 differentially expressed (DE) miRNAs, were identified among longissimus dorsi from three growth stages (2, 9, and 24 months) by miRNA sequencing. Combining analysis of the DE mRNAs and DE miRNAs was then performed by miRDB and miRwalk, and miR-145-5p and FOXO1, miR-487b-3p, and PPARG coactivator 1 α (PPARGC1A), miR-345-3p, and solute carrier family 2 member 4 (SLC2A4), etc. were shown to closely associate with lipid metabolism, which was then validated by a correlation analysis. The final DE mRNAs were significantly enriched in fatty acid transmembrane transport, fatty acid homeostasis, apelin signaling pathway, glucagon signaling pathway, insulin signaling pathway, and AMPK signaling pathway by gene ontology and Kyoto Encyclopedia of Genes and Genomes analysis. Besides, miR-145-5p showed a certain effect on goat intramuscular fat metabolism by acting on the possible target gene Forkhead Box O1 (FOXO1). These data provide some theoretical support for improving the quality of goat meat.

Impact of rumen microbiome on cattle carcass traits

Rumen microbes are crucial in the anaerobic fermentation of plant polysaccharides to produce volatile fatty acids. However, limited information exists about the specific microbial species and strains in the rumen that affect carcass traits, and it is unclear whether there is a relationship between rumen metabolic functions and these traits. This study investigated the relationship between the rumen microbiome and carcass traits in beef cattle using 16S rRNA amplicon and shotgun sequencing. Metagenomic sequencing was used to compare the rumen microbiome between high-carcass weight (HW) and low-carcass weight (LW) cattle, and high-marbling (HM) and low-marbling (LM) cattle. Prokaryotic communities in the rumen of HW vs. LW and HM vs. LM were separated using 16S rRNA amplicon sequencing. Notably, shotgun metagenomic sequencing revealed that HW cattle had more methane-producing bacteria and ciliate protozoa, suggesting higher methane emissions. Additionally, variations were observed in the abundances of certain glycoside hydrolases and polysaccharide lyases involved in the ruminal degradation of plant polysaccharides between HW and LW. From our metagenome dataset, 807 non-redundant metagenome-assembled genomes (MAGs) of medium to high quality were obtained. Among these, 309 and 113 MAGs were associated with carcass weight and marbling, respectively.

Molecular and Cellular Mechanisms of Intramuscular Fat Development and Growth in Cattle

Intramuscular fat, also referred to as marbling fat, is the white fat deposited within skeletal muscle tissue. The content of intramuscular fat in the skeletal muscle, particularly the longissimus dorsi muscle, of cattle is a critical determinant of beef quality and value. In this review, we summarize the process of intramuscular fat development and growth, the factors that affect this process, and the molecular and epigenetic mechanisms that mediate this process in cattle. Compared to other species, cattle have a remarkable ability to accumulate intramuscular fat, partly attributed to the abundance of sources of fatty acids for synthesizing triglycerides. Compared to other adipose depots such as subcutaneous fat, intramuscular fat develops later and grows more slowly. The commitment and differentiation of adipose precursor cells into adipocytes as well as the maturation of adipocytes are crucial steps in intramuscular fat development and growth in cattle. Each of these steps is controlled by various factors, underscoring the complexity of the regulatory network governing adipogenesis in the skeletal muscle. These factors include genetics, epigenetics, nutrition (including maternal nutrition), rumen microbiome, vitamins, hormones, weaning age, slaughter age, slaughter weight, and stress. Many of these factors seem to affect intramuscular fat deposition through the transcriptional or epigenetic regulation of genes directly involved in the development and growth of intramuscular fat. A better understanding of the molecular and cellular mechanisms by which intramuscular fat develops and grows in cattle will help us develop more effective strategies to optimize intramuscular fat deposition in cattle, thereby maximizing the quality and value of beef meat.

Effect of Post-Weaning Concentrate Feeding Prior to Forage Finishing on Intramuscular Fat Deposition

The objectives of this study were to examine the effects of feeding high-concentrate diets post-weaning (PW) prior to forage finishing on (1) changes in ultrasound intramuscular fat deposition and lipogenic/lipolytic gene expression during the post-weaning phase and (2) carcass characteristics and fatty acid composition after forage finishing to 487 kg. Steers were randomly assigned to one of four treatments (PW0, PW40, PW80, and PW120) at weaning to examine the time of high-concentrate feeding prior to forage finishing. The ultrasound intramuscular fat content was greater (p < 0.05) for PW120 compared to those for PW0, PW40, or PW80 at the end of the post-weaning phase. Feeding high concentrates (PW120) up-regulated (p < 0.01) the mRNA expression of fatty acid transporters and lipogenic genes and down-regulated lipolytic genes in the LM compared to PW0. Carcasses from PW120 were graded 83% Choice (p = 0.025), whereas carcasses from other post-weaning treatments (PW0, 40, or 80) were graded 25, 36, and 54% Choice, respectively, at the final harvest. The total fatty acid content of the muscle at slaughter was greater (p = 0.0004) for PW120 than PW0, PW40, and PW80. Feeding high-concentrate diets to steers post-weaning for 120 day enhanced early intramuscular fat deposition without causing major changes to the fatty acid composition of the longissimus muscle after forage finishing.

Do carcass traits influence consumer perception of pork eating quality?

The objective of this study was to assess carcass traits' influence on pork eating quality as evaluated by consumers. A total of 1360 pork chops were used, with 824 from the sirloin end and 536 from the butt end of the loin (Longissimuss thoracis et lumborum), to produce 340 packages, each containing four pork chops. Untrained participants received one package of either sirloin or butt chops, being two pork chops from barrows and two from gilts. Participants answered a survey rating the tenderness, juiciness, flavour, and overall acceptability of each chop on an 8-point scale. Correlation analysis was conducted between carcass traits and pork eating quality attributes. For the descriptive analysis, classes (low, medium, and high) for carcass traits, Warner-Bratzler shear force (WBSF) and cooking loss were created based on our consumer responses dataset for palatability attributes. No significant correlations (P > 0.05) were observed between carcass traits and pork eating quality traits. Tenderness and overall acceptability were negatively correlated (P < 0.05) with cooking loss and WBSF. Loin intramuscular fat (IMF) content showed a weak negative correlation (P < 0.05) with WBSF and cooking loss. Consumers rated chops from the high and medium/high backfat thickness and loin IMF classes slightly higher for tenderness and juiciness, respectively. Additionally, chops from the low and/or medium WBSF and cooking loss classes received slightly higher scores for tenderness and juiciness than pork chops in the high classes. In conclusion, the study indicated that carcass traits had minimal impact on overall acceptability of pork by consumers.

Gga-let-7a-3p inhibits the proliferation and differentiation of chicken intramuscular preadipocytes

1. Intramuscular fat (IMF) is a key parameter for chicken meat quality. IMF deposition is driven by genetic, nutritional and management factors, with genetics being the determining factor. Previous whole transcriptome sequencing revealed that microRNA gga-let-7a-3p was related to lipid metabolism in breast muscle. This study further investigated the potential role of gga-let-7a-3p in IMF deposition.2. The mimic and inhibitor of gga-let-7a-3p were individually transfected into chicken intramuscular preadipocytes. Subsequently, the proliferation and differentiation states of the cells were detected. Transcriptome sequencing was performed on cells transfected with gga-let-7a-3p mimic.3. The results indicated that gga-let-7a-3p suppressed the mRNA levels of proliferation and differentiation-related genes, as well as the protein levels. EdU and Oil Red O assays revealed that gga-let-7a-3p restrained preadipocyte proliferation and differentiation. In addition, a total of 333 up-regulated genes and 807 down-regulated genes were identified in cells transfected with gga-let-7a-3p mimic. Using Kyoto Encyclopaedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analysis, differential genes were found to be enriched in processes such as the peroxisome proliferator activated receptor (PPAR) signalling pathway and oxidative phosphorylation.4. The study demonstrated that gga-let-7a-3p inhibits the proliferation and differentiation of chicken intramuscular preadipocytes, which provides new understanding to further unravel the function of gga-let-7a-3p.

Growth Performance, Blood Metabolites and Carcass Characteristics of Black Goat Kids Fed Diets Containing Olive Cake

This study investigated the dietary effect of incorporating different levels of olive cake (OC) on the metabolic responses, growth performance, and carcass characteristics of black goat male kids. Thirty kids (body weight = 17.3 ± 0.40 kg) were randomly distributed into one of three equally sized dietary groups: a control diet (CON), OC at 75 g/kg (OC75), and OC at 150 g/kg (OC150) of dietary dry matter (DM). The results revealed that the intake of DM, crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) was similar (p ≥ 0.11) among the three treatment groups. However, the OC150 group had the greatest (p < 0.0001) ether extract (EE) intake compared to the OC75 and CON groups. The growth measurements were similar (p ≥ 0.13) among the three groups. Feed efficiency was not affected by the inclusion of OC. In contrast to the CON diet, the cost of gain was, however, reduced (p = 0.004) in the OC diets. All three treatment groups' digestibility of DM, CP, and ADF was similar. However, when compared to the OC75 and CON groups, the digestibility of NDF was better (p < 0.05) in the OC150 group. The N intake did not differ among the three experimental groups. Nitrogen retained as g/d was higher (p = 0.04) in the OC150 and OC75 groups compared to the CON group, while retention as a percentage (g/100 g) was similar among the three groups. Except for intermuscular fat, total fat, leg fat depth, and tissue depth, the inclusion of OC did not result in any discernible treatment effects on the carcass and meat quality parameters. Only alanine aminotransferase enzyme activity was lower (p < 0.0001) in OC-treated groups compared to the CON group. In summary, incorporating OC at 75 g/kg and 150 g/kg levels into the diets of black goat kids had positive comparable effects on some parameters related to growth performance, carcass attributes, and meat quality. Importantly, utilizing olive cake led to cost savings in production and may serve as a viable alternative feed source in goat nutrition.

RNA-Seq Analysis Revealed circRNAs and Genes Associated with Abdominal Fat Deposition in Ducks

Fat deposition is an important factor affecting meat quality and feed conversion efficiency in meat ducks. This study aims to identify key circRNAs and genes affecting abdominal fat deposition. The correlations between abdominal fat and other growth performances were analyzed in 304 F2 generation of Cherry Valley duck Runzhou Crested White ducks, and an RNA-seq analysis of abdominal fat tissues from ducks with high and low rates of abdominal fat was performed. Growth performance results showed that Abdominal fat ratio and Intramuscular fat were significantly higher in the high rates of abdominal fat (HF)group than in the low rates of abdominal fat (LF) group for ducks. RNA-seq analysis of abdominal fat tissue unveiled 85 upregulated and 72 downregulated circRNAs among the differentially expressed ones. Notably, 74 circRNAs displayed more than four-fold differential expression, constituting 47.13% of the differentially expressed genes. Functional enrichment analysis of the differentially expressed circRNA source and target genes indicated that 17 circRNAs might partake in regulating duck abdominal fat production by influencing pathways like PPAR signaling, lipid droplets, and triglyceride metabolism. Lastly, multiple circRNA-microRNA-messenger RNA interaction networks were constructed. The results of this study establish the groundwork for understanding the molecular mechanisms that regulate abdominal fat deposition in ducks, offering a theoretical reference for the selective breeding of high-quality meat-producing ducks.

Muscle, season, sex, and carcass weight affected pork texture, collagen characteristics, and intramuscular fat content

In this study, pigs from 3 supply chains were slaughtered in an Australian summer and winter (n = 20 for each supply chain). The pigs were from 2 sexes (female and castrated male) and 2 carcass weight groups (high: 95.0 to 100.0 kg and low: 75.0 to 80.0 kg). From each carcass, the Biceps femoris (BF), Longissimus thoracis et lumborum (LTL), and Triceps brachii (TB) were excised at 24 h postmortem, vacuum packed, frozen at 24-48 h and transported to the lab. Cooking loss, Warner-Bratzler shear force (WBSF) and texture profile analysis (adhesiveness, chewiness, cohesiveness, hardness, resilience, and springiness) were measured in LTL and BF. pH, collagen content, and solubility and intramuscular fat (IMF) content were determined for all muscles. Results showed that BF was tougher than LTL, and winter samples were tougher than summer ones (P < 0.05). The TB had higher pH, collagen, and IMF content than BF and LTL (P < 0.05). Collagen solubility was higher in castrated male and winter samples. pH, collagen solubility, and IMF content were significantly (P < 0.05) related to chewiness and hardness in pork BF and LTL. pH and IMF were also related to cooking loss, while collagen solubility and IMF were related to WBSF (P < 0.05). The relationships of pH and IMF with pork texture were predominantly driven by the LTL, while the relationships between collagen solubility and texture were predominantly driven by the BF. Collagen solubility and IMF of pork BF and TB were related to those of LTL, but the correlations were not strong enough for prediction. Pork texture and chemical components were affected by muscle, seasons, sex and carcass weight. pH, collagen solubility, and IMF-affected pork texture.

Investigation on muscle fiber types and meat quality and estimation of their heritability and correlation coefficients with each other in four pig populations

The aim of this study was to investigate the muscle fiber types and meat quality in four populations and estimate the heritability and correlation coefficients of those traits in Shanxia long black pig (SX). In this study, a total of 318 pigs were recorded for 16 traits of the muscle fiber types and meat quality in four populations, including 256 individuals from the new breed SX. The population had a significant effect on all recorded traits, and the meat quality of the Lulai black pig was better than the remaining populations. The heritability (h2 ) of meat quality traits was from 0.06 (pH at 24 h) to 0.47 (shearing force), and the muscle fiber types belonged to the traits with low to medium heritability. The density of total fiber had the highest h2 (0.40), while the percentage of type IIA had the lowest h2 (0.04). Most traits are phenotypically correlated with each other, but only a small proportion of traits are genetically correlated with each other. None fiber type genetically correlated with meat quality significantly, because the genetic correlation coefficients had large standard errors. These results provided some insights into genetic improvements for the meat quality in pig breeds and also indicated that the parameters of muscle fiber characteristics can explain parts of the variation in meat quality.

Genetic lines influenced the texture, collagen and intramuscular fat of pork longissimus and semimembranosus

The effects of genetic lines (PM-LR - Pure maternal, Landrace-type; PM-LW - Pure maternal, Large White-type; PM-D - Pure maternal, Duroc-type; SynT-LWLR - Synthetic terminal, Large white and Landrace-type; PT-D - Pure terminal, Duroc-type; and PT-LW - Pure terminal, Large White-type) on carcass traits and pork quality, including cooking loss, Warner-Bratzler shear force (WBSF), texture profile analysis (TPA), collagen content and solubility and intramuscular fat (IMF) content of Longissimus thoracis et lumborum (LTL) and Semimembranosus (SM), were investigated. The results showed that all terminal lines had lower backfat thickness than maternal lines, but muscles from line SynT-LWLR had the highest hardness and cohesiveness and the lowest IMF content. The SM showed higher hardness, adhesiveness, springiness, chewiness, collagen, and IMF content but lower WBSF and collagen solubility than LTL. Collagen and IMF content affected WBSF and TPA parameters across both muscles and in LTL alone. Significant relationships between collagen content and texture parameters were found in line PT-D. Genetic lines and muscles affect the contribution of collagen and IMF to pork texture.

Effects of Adipose Tissue-Specific Knockout of Delta-like Non-Canonical Notch Ligand 1 on Lipid Metabolism in Mice

Delta-like non-canonical Notch ligand 1 (DLK1), which inhibits the differentiation of precursor adipocytes, is a recognized marker gene for precursor adipocytes. Lipids play a crucial role in energy storage and metabolism as a vital determinant of beef quality. In this study, we investigated the mechanism of the DLK1 gene in lipid metabolism by constructing adipose tissue-specific knockout mice. We examined some phenotypic traits, including body weight, liver coefficient, fat index, the content of triglyceride (TG) and cholesterol (CHOL) in abdominal white adipose tissue (WAT) and blood. Subsequently, the fatty acid content and genes related to lipid metabolism expression were detected in DLK1-/- and wild-type mice via GC-MS/MS analysis and quantitative real-time PCR (qRT-PCR), respectively. The results illustrated that DLK1-/- mice exhibited significant abdominal fat deposition compared to wild-type mice. HE staining and immunohistochemistry (IHC) results showed that the white adipocytes of DLK1-/- mice were larger, and the protein expression level of DLK1-/- was significantly lower. Regarding the blood biochemical parameters of female mice, DLK1-/- mice had a strikingly higher triglyceride content (p < 0.001). The fatty acid content in DLK1-/- mice was generally reduced. There was a significant reduction in the expression levels of the majority of genes that play a crucial role in lipid metabolism. This study reveals the molecular regulatory mechanism of fat metabolism in mice and provides a molecular basis and reference for the future application of the DLK1 gene in the breeding of beef cattle with an excellent meat quality traits. It also provides a molecular basis for unravelling the complex and subtle relationship between adipose tissue and health.

Production and meat quality traits of genetically lean immunocastrated pigs naturally divergent for loin tenderness

Warner-Bratzler Shear Force (WBSF) is a quantitative measurement of meat toughness that has great impact on the consumer acceptability of meat. This study was conducted to evaluate growth performance, carcass and meat quality characteristics, and fatty acids profile of longissimus lumborum (LL) intramuscular fat (IMF) of pigs that are genetically divergent for WBSF. Based on WBSF values of the LL from a previous study, 12 immunocastrated male pigs selected from 96 pigs were divided into two groups with high WBSF (53.28 to 42.50 N) and low WBSF (37.27 to 27.79 N). Although high-WBSF pigs tended to have improved (P = 0.08) gain-to-feed ratio, overall performance was similar between WBSF groups. High-WBSF pigs also tended to have higher (P = 0.09) cooling loss and lean percentage as well as decreased (P = 0.08) 10th-rib backfat depth than low-WBSF pigs. Loins from high-WBSF pigs tended to have lower (P = 0.07) IMF content and higher (P = 0.09) cooking loss than low-WBSF pigs. Compared to low-WBSF pigs, IMF of the LL from high-WBSF pigs had lower (P = 0.05) percentage of oleic acid and tended to have a decreased (P = 0.07) percentage of total monounsaturated fatty acids. Loins from pigs with high WBSF tended to have increased (P = 0.09) total polyunsaturated fatty acids (PUFA) content and had higher (P = 0.03) PUFA: saturated fatty acid ratio than low-WBSF pigs. Selecting pigs for pork tenderness could potentially conflict with lean growth efficiency and a healthier fatty acids profile for human consumption.

Identification of a Candidate Gene Regulating Intramuscular Fat Content in Pigs through the Integrative Analysis of Transcriptomics and Proteomics Data

Pork is a widely consumed source of animal protein worldwide, and the intramuscular fat (IMF) content in pork plays a crucial role in determining its quality. In this study, we sought to identify candidate genes that regulate IMF deposition in pigs. We performed tandem mass tags (TMT)-based quantitative proteomics analysis using Longissimus dorsi (LD) muscle samples obtained from eight pigs with extremely high and low IMF content among a group of 28 Duroc pigs and identified 50 differentially abundant proteins (DAPs). Additionally, we compared the proteomics data with RNA-sequencing data obtained in our previous study and identified TUSC5 as a differentially expressed gene corresponding to the relevant DAP. To investigate the potential role of TUSC5 in adipogenesis, we suppressed TUSC5 expression in mouse 3T3-L1 preadipocytes using short hairpin RNA (shRNA) and observed a significant reduction in the differentiation of 3T3-L1 cells into adipocytes, as indicated by Oil Red O staining and triglyceride content. Moreover, we observed a reduction in the expression of genes associated with adipogenesis (PPARG, CEBPA, FABP4, and FASN) following TUSC5 suppression. Through an integrative analysis of transcriptomics and proteomics data, our study identified TUSC5 as a crucial candidate gene associated with the regulation of IMF content in pigs.

Diacylglycerol acyltransferase 2 promotes the adipogenesis of intramuscular preadipocytes in goat

Diacylglycerol acyltransferase 2 (DGAT2) is the key enzyme that catalyzes the last step of triglyceride synthesis. However, its role in intramuscular fat (IMF) deposition in goat remains unclear. The purpose of this study was to explore the role of DGAT2 in regulating goat IMF deposition. In the present study, the expression of DGAT2 was highest in goat triceps brachii, and highest on the first day after oleic acid induction in goat intramuscular preadipocytes. The overexpression of DGAT2 promoted the accumulation of lipid droplets and triglyceride synthesis, accompanied by the expression upregulation of DGAT1, TIP47, ACC and ACOX1 significantly, and expression downregulation of AGPAT6, LPIN1, LPL, HSL, ATGL and ADRP significantly. In contrast, the silencing of DGAT2 decreased the accumulation of lipid droplets, inhibited the expression of DGAT1, GPAM, ADRP, AGPAT6, LPL, HSL, ATGL, ACC, FASN, ACOX1 significantly, and enhanced that of TIP47 significantly. Overall, these data underscore DGAT2 may play a potentially important role in lipid droplets formation and triglyceride accumulation, so as to maintain intramuscular fat deposition, beyond triglyceride synthesis in goat.

Effect of bovine myosin heavy chain 3 on proliferation and differentiation of myoblast

The myosin heavy chain 3 (MYH3) gene is an essential gene that affects muscle development. This study aimed to discuss the expression characteristics of the MYH3 gene and its effect on the proliferation and differentiation of bovine myoblasts. Quantitative real time-PCR results display that the expression level of MYH3 was higher in muscle tissue, and the expression increased in the early stage of myoblast differentiation. Interfering with the MYH3 gene in myoblasts resulted in fewer EDU-positive cells and decreased expression of proliferation marker genes. Interference with MYH3 can also affect the differentiation process of myoblasts. Regarding phenotype, myotube differentiation in the interference group was slowed or even stopped. Interference with the expression of MYH3 could significantly reduce the expression of myogenic differentiation marker genes. The above results show that MYH3 is mainly expressed in muscle tissue and is highly expressed in the early stage of differentiation of bovine myoblasts, and interfering with the MYH3 can promote the proliferation and inhibit the differentiation of bovine myoblasts. This study provides a theoretical basis for revealing the regulatory process of bovine myoblast proliferation and differentiation and bovine molecular breeding.

Properties of texturized protein and performance of different protein sources in the extrusion process: A review

The need for protein is increasing due to the rapid growth of the global population. However, conventional animal meat production has caused severe environmental, land usage, and other issues. Meat substitutes can provide consumers with a high-quality alternative to protein. Texturized protein (TP) is a critical ingredient in meat substitutes and is mainly obtained through extrusion processing. Therefore, this review first discussed the essential physical properties of TP, including appearance and structure, water-holding capacity (WHC) and oil-holding capacity (OHC), texture, and sensory properties. The performance of plant and novel source proteins in extrusion processing is also summarized. The properties of the desired TP should be considered first before extrusion processing. Under different extrusion parameters, proteins from the same source can exhibit varying properties. Although the novel source proteins can adversely affect TP quality, their high yield and environmental protection are worthy of further study. This paper aims to review the impact of proteins from different sources on the properties of TP during the extrusion process and discuss practical research methods for TP.

PDZK1-interacting protein 1(PDZK1IP1) promotes subcutaneous preadipocyte proliferation in goats

PDZK1-interacting protein 1(PDZK1IP1), also known as MAP17, is encoded by the PDZK1IP1 gene and is a membrane-associated protein. PDZK1IP1 have been proven to be a potent regulator of cancer cell proliferation. However, the role of PDZK1IP1 in regulating goat subcutaneous preadipocyte proliferation is unknown. Here, we cloned the full-length coding sequence of PDZK1IP1 gene, investigated the potential functional of PDZK1IP1 in goat subcutaneous preadipocyte proliferation by gaining or losing function in vitro. Our results indicated that goat PDZK1IP1 gene consists of 345 bp, encoding a protein of 114 amino acids containing a typical PDZK1IP1 (MAP17) super family domain. Overexpression of PDZK1IP1 significantly increased the number of EdU-positive cells and cell viability, and also upregulated mRNA expression of cell proliferation-associated genes including CCND1 and CDK2 in vitro cultured cells. Conversely, knockdown of PDZK1IP1 mediated by siRNA technique significantly inhibited subcutaneous preadipocyte proliferation and downregulated mRNA expression of cell proliferation-associated genes including CCNE1, CCND1 and CDK2. Collectively, these results suggested that PDZK1IP1 can promote proliferation of goat subcutaneous preadipocyte.

Carcass traits, proximate composition, amino acid and fatty acid profiles, and mineral contents of meat from Cherry Valley, Chinese crested, and crossbred ducks

Duck meat is known for its taste and high nutritive value. To preserve local genetic diversity while maintaining commercial viability, we obtained a crossbreed (CB) between high-performing Cherry Valley (CV) and traditional Chinese crested (CC) ducks. We compared carcass traits and meat quality characteristics of CB and parental breeds. Meat from the above ducks at their respective marketable ages was evaluated for proximate composition, amino acid and fatty acid profiles, and selected mineral content. The live weights, carcass weights, and breast muscle percentage of CB were higher than CC but lower than CV; the leg muscle of CB was lower than CV and CC. CB had higher intramuscular fat content than CV; its collagen content was lower than CC but higher than CV in breast and thigh muscles. Additionally, the saturated fatty acid content of CB muscle was lower than CV and higher than CC. CB contained more monounsaturated fatty acids than CV and CC. Zn content was higher in CB breast than CV and CC. CB, obtained by crossing CV and CC, has partial advantages over both the breeds suggesting that these characteristics aligned with standards to breed ducks with high-quality meat.

Cloning of goat PGAM2 gene and its overexpression promotes the differentiation of intramuscular preadipocytes

As a member of the PGAMs family, PGAM2 has been proved to catalyze the reversible reaction of 3-phosphoglycerate (3-PGA) to 2-phosphoglycerate (2-PGA) in the glycolytic pathway. However, it is unclear whether PGAM2 has a role in regulating differentiation in goat intramuscular preadipocytes. Here, this study was carried to clone the open reading frame (ORF) of goat PGAM2, elucidate its molecular and expressional characteristics, and evaluate the involvement in adipogenesis of intramuscular preadipocytes. According to our findings, the cloned goat PGAM2 gene was 784 bp in full length, including 762 bp of ORF and encoding a protein of 253 amino acids. The expressional level of PGAM2 peaked at 48 hours after induced adipogenic differentiation and was highest in the skeletal muscle of triceps. Moreover, overexpression of PGAM2 transfected by its overexpression plasmid promotes lipid accumulation of goat intramuscular adipocyte as shown by Oil Red O and bodipy staining, accompanied by up-regulating the mRNA levels of peroxisome proliferator-activated receptor γ (PPARγ) (p < 0.001), sterol regulatory element-binding protein 1 (SREBP1) (p < 0.001), CCAAT/Enhancer-binding protein α (C/EBPα) (p < 0.01) and lipoprotein lipase (LPL) (p < 0.01). Taken together, these findings indicate that PGAM2 is a positive regulator for goat intramuscular adipocytes and provide new insights into improvement intramuscular fat deposition in goat meat.

Rosiglitazone-induced PPARγ activation promotes intramuscular adipocyte adipogenesis of pig

Intramuscular fat (IMF) positively influences various aspects of meat quality, while the subcutaneous fat (SF) has negative effect on carcass characteristics and fattening efficiency. Peroxisome proliferator-activated receptor gamma (PPARγ) is a key regulator of adipocyte differentiation, herein, through bioinformatic screen for the potential regulators of adipogenesis from two independent microarray datasets, we identified that PPARγ is a potentially regulator between porcine IMF and SF adipogenesis. Then we treated subcutaneous preadipocytes (SA) and intramuscular preadipocytes (IMA) of pig with RSG (1 µmol/L), and we found that RSG treatment promoted the differentiation of IMA via differentially activating PPARγ transcriptional activity. Besides, RSG treatment promoted apoptosis and lipolysis of SA. Meanwhile, by the treatment of conditioned medium, we excluded the possibility of indirect regulation of RSG from myocyte to adipocyte and proposed that AMPK may mediate the RSG-induced differential activation of PPARγ. Collectively, the RSG treatment promotes IMA adipogenesis, and advances SA lipolysis, this effect may be associated with AMPK-mediated PPARγ differential activation. Our data indicates that targeting PPARγ might be an effective strategy to promote intramuscular fat deposition while reduce subcutaneous fat mass of pig.

Effect of TEA domain transcription factor 1 (TEAD1) on the differentiation of intramuscular preadipocytes in goats

TEA domain transcription factor 1 (TEAD1), also called TEF-1, acts as a transcriptional enhancer to regulate muscle-specific gene expression. However, the role of TEAD1 in regulating intramuscular preadipocyte differentiation in goats is unclear. The aim of this study was to obtain the sequence of TEAD1 gene and elucidate the effect of TEAD1 on goat intramuscular preadipocyte differentiation in vitro and its possible mechanism. The results showed that the goat TEAD1 gene CDS region sequence was 1311 bp. TEAD1 gene was widely expressed in goat tissues, with the highest expression in brachial triceps (p < 0.01). The expression of TEAD1 gene in goat intramuscular adipocytes at 72 h was extremely significantly higher than that at 0 h (p < 0.01). Overexpression of goat TEAD1 inhibited the accumulation of lipid droplets in goat intramuscular adipocyte. The relative expression of differentiation marker genes SREBP1, PPARγ, C/EBPβ were significantly down-regulated (all p < 0.01), but PREF-1 was significantly up-regulated (p < 0.01). Binding analysis showed that there were multiple binding sites between the DNA binding domain of goat TEAD1 and the promoter binding region of SREBP1, PPARγ, C/EBPβ and PREF-1. In conclusion, TEAD1 negatively regulates the differentiation of goat intramuscular preadipocytes.

Cloning and functional characterization of porcine AACS revealing the regulative roles for fat deposition in pigs

Fat deposition is a quantitative trait controlled by multiple genes in pigs. Using transcriptome sequencing, we previously reported that AACS is differentially expressed in the subcutaneous fat tissue of Dingyuan pigs with divergent backfat thickness. Therefore, with the aim of further characterizing this gene and its protein, we cloned the entire 3286-bp mRNA sequence of the porcine AACS, and the encoded AACS protein is a hydrophilic protein without a signal peptide or transmembrane sequence. Our findings suggested that among various tissues and pig breeds, AACS was highly expressed in subcutaneous fat. We have identified three completely linked SNP loci in the AACS gene: A-1759C, C-1683T, and A-1664G. The double luciferase activity test in the 5' flanking region indicated that the flanking region of AACS contained several active regulatory elements. The three linked SNPs that were identified in one of the critical active elements, and might serve as important molecular markers regulating backfat thickness. Finally, we observed that AACS overexpression inhibited the proliferation and differentiation of subcutaneous preadipocytes. Collectively, our results suggest that AACS inhibits subcutaneous fat deposition in pigs. This study provides a new molecular marker for understanding the mechanism of porcine fat deposition.

FOS Inhibits the Differentiation of Intramuscular Adipocytes in Goats

Goat intramuscular fat (IMF) deposition is precisely regulated by many key genes as well as transcription factors. Nevertheless, the potential of the regulators of goat IMF deposition remains undefined. In this work, we reported that the transcription factor FOS is expressed at a low level at the early differentiation stage and at a high level in late differentiation. The overexpression of FOS inhibited intramuscular adipocyte lipid accumulation and significantly downregulated the expressions of PPARγ, C/EBPβ, C/EBPα, AP2, SREBP1, FASN, ACC, HSL, and ATGL. Consistently, the knockdown of FOS, facilitated by two distinct siRNAs, significantly promoted intramuscular adipocyte lipid accumulation. Moreover, our analysis revealed multiple potential binding sites for FOS on the promoters of PPARγ, C/EBPβ, and C/EBPα. The expression changes in PPARγ, C/EBPβ, and C/EBPα during intramuscular adipogenesis were opposite to that of FOS. In summary, FOS inhibits intramuscular lipogenesis in goats and potentially negatively regulates the expressions of PPARγ, C/EBPβ, and C/EBPα genes. Our research will provide valuable data for the underlying molecular mechanism of the FOS regulation network of intramuscular lipogenesis.

Identification of key genes related to intramuscular fat deposition in Beijing-You chicken by mRNA and miRNA transcriptome analysis

Intramuscular fat (IMF) is an important factor affecting chicken quality. However, the age-related mechanism of IMF deposition has not yet been elucidated. In this study, the IMF, phospholipids (PL), triglycerides (TG), and fatty acid (FA) content in the breast muscle of Beijing-You chicken (BJY) at 1, 56, 98, and 120 d of age was measured, and mRNA and miRNA sequencing was integrated to explore the regulatory genes of IMF deposition. The results showed that the IMF content of BJY at 1 d of age was significantly higher than that at later stage of birth (P < 0.05). The transcriptome sequencing results showed that 7, 225 differentially expressed genes (DEGs) and 243 differentially expressed miRNAs (DE-miRNAs) were identified. The cluster analysis showed that the expression of DEGs and DE-miRNAs at 1 d of age was significantly different from that at later stages of birth. Furthermore, a potential mRNA-miRNA regulatory network related to IMF deposition was established by weighted gene co-expression network analysis (WGCNA); gga-miR-29c-3p-PIK3R1, gga-miR-6701-3p-PTEN, gga-miR-363-3p-PTEN, gga-miR-1563-WWP1, gga-miR-449c/d-5p-TRAF6, and gga-miR-6701-3p-BMPR1B were identified as key mRNA-miRNA pairs for the regulation of IMF deposition. These results will help elucidate the mechanism of IMF formation mediated by miRNAs in chickens, and provide a theoretical foundation for the genetic improvement of broiler meat quality.