Marbling Traits Research Articles

Identification of several lncRNA-mRNA pairs associated with marbling trait between Nanyang and Angus cattle

BackgroundThe marbling trait of cattle muscles, being a key indicator, played an important role in evaluating beef quality. Two breeds of cattle, namely a high-marbling (Angus) and a low-marbling (Nanyang) one, with their cattle muscles selected as our samples for transcriptome sequencing, were aimed to identify differentially expressed long non-coding RNAs (lncRNAs) and their targets associated with the marbling trait.ResultsTranscriptome sequencing identified 487 and 283 differentially expressed mRNAs and lncRNAs respectively between the high-marbling (Angus) and low-marbling (Nanyang) cattle muscles. Twenty-seven pairs of differentially expressed lncRNAs-mRNAs, including eighteen lncRNAs and eleven target genes, were found to be involved in fat deposition and lipid metabolism. We established a positive correlation between fourteen up-regulated (NONBTAT000849.2, MSTRG.9591.1, NONBTAT031089.1, MSTRG.3720.1, NONBTAT029718.1, NONBTAT004228.2, NONBTAT007494.2, NONBTAT011094.2, NONBTAT015080.2, NONBTAT030943.1, NONBTAT021005.2, NONBTAT021004.2, NONBTAT025985.2, and NONBTAT023845.2) and four down-regulated (NONBTAT000850.2, MSTRG.22188.3, MSTRG.22188.4, and MSTRG.22188.5) lncRNAs and eleven genes related to adiponectin family protein (ADIPOQ), cytochrome P450 family (CYP4V2), 3-hydroxyacyl-CoA dehydratase family (HACD4), kinesin family (KIF5C), lipin family (LPIN2), perilipin family (PLIN1), prostaglandin family (PTGIS), solute carrier family (SLC16A7, SLC2213, and SLCO4C1), and containing a transmembrane domain protein family (VSTM1).ConclusionsThese candidate genes and lncRNAs can be regarded as being responsible for regulating the marbling trait of cattle. lncRNAs along with the variations in intramuscular fat marbling established a foundation for elucidating the genetic basis of high marbling in cattle.

Comparing algorithms to approximate accuracies for single-step genomic best linear unbiased predictor.

The exact accuracy of estimated breeding values can be calculated based on the prediction error variances obtained from the diagonal of the inverse of the left-hand side (LHS) of the mixed model equations (MME). However, inverting the LHS is not computationally feasible for large datasets, especially if genomic information is available. Thus, different algorithms have been proposed to approximate accuracies. This study aimed to: 1) compare the approximated accuracies from 2 algorithms implemented in the BLUPF90 suite of programs, 2) compare the approximated accuracies from the 2 algorithms against the exact accuracy based on the inversion of the LHS of MME, and 3) evaluate the impact of adding genotyped animals with and without phenotypes on the exact and approximated accuracies. Algorithm 1 approximates accuracies based on the diagonal of the genomic relationship matrix (G). In turn, algorithm 2 combines accuracies with and without genomic information through effective record contributions. The data were provided by the American Angus Association and included 3 datasets of growth, carcass, and marbling traits. The genotype file contained 1,235,930 animals, and the pedigree file contained 12,492,581 animals. For the genomic evaluation, a multi-trait model was applied to the datasets. To ensure the feasibility of inverting the LHS of the MME, a subset of data under single-trait models was used to compare approximated and exact accuracies. The correlations between exact and approximated accuracies from algorithms 1 and 2 of genotyped animals ranged from 0.87 to 0.90 and 0.98 to 0.99, respectively. The intercept and slope of the regression of exact on approximated accuracies from algorithm 2 ranged from 0.00 to 0.01 and 0.82 to 0.87, respectively. However, the intercept and the slope for algorithm 1 ranged from -0.10 to 0.05 and 0.98 to 1.10, respectively. In more than 80% of the traits, algorithm 2 exhibited a smaller mean square error than algorithm 1. The correlation between the approximated accuracies obtained from algorithms 1 and 2 ranged from 0.56 to 0.74, 0.38 to 0.71, and 0.71 to 0.97 in the groups of genotyped animals, genotyped animals without phenotype, and proven genotyped sires, respectively. The approximated accuracy from algorithm 2 showed a closer behavior to the exact accuracy when including genotyped animals in the analysis. According to the results, algorithm 2 is recommended for genetic evaluations since it proved more precise.

233 Feeding and Managing Dairy Cattle Genetics for Beef

Abstract The contribution of dairy steers to the U.S. fed beef supply has increased over the last 2 decades. In part, due to declining beef cow numbers and increased use of sexed dairy semen to produce genetically superior replacement heifers from the best dairy cows in the herd. Raising dairy cattle for beef production offers unique opportunities and challenges when compared with feeding native beef cattle. Dairy steers offer predictable and uniform feedlot performance (ADG, DMI, G:F) as a group, and improved quality grades compared with their native beef counterparts. However, dairy steers yield less red meat compared with native beef cattle due to a greater ratio of bone to muscle, internal fat, organ size, and gastrointestinal tract weight. Dairy steers present carcass size problems in the beef packing industry, with Holstein carcasses being too long and Jersey carcasses being light weight. Beef × dairy crossbreeding strategies are being implemented on some dairy farms to increase the income generated from bull calves and to improve the feed efficiency and yield of beef produced from the U.S. dairy herd. This new model of beef production from the dairy herd is not without its challenges. Early beef × dairy crossbreeding efforts have demonstrated variable results. Successful adoption of beef × dairy crossbreeding in the cattle industry will depend on the proper selection of beef sires that excel in calving ease, growth, muscling, and marbling traits to complement the challenges realized with dairy genetics involved in beef production.

Characterization of novel lncRNA muscle expression profiles associated with meat quality in beef cattle.

The aim of this study was to identify novel lncRNA differentially expressed (DE) between divergent animals for beef tenderness and marbling traits in Nellore cattle. Longissimus thoracis muscle samples from the 20 most extreme bulls (of 80 bulls set) for tenderness, tender (n = 10) and tough (n = 10) groups, and marbling trait, high (n = 10) and low (n = 10) groups were used to perform transcriptomic analysis using RNA‐Sequencing. For tenderness, 29 lncRNA were DE (p‐value ≤ 0.01) in tough beef animals in relation to tender beef animals. We observed that genic lncRNAs, for example, lncRNA_595.1, were overlapping exonic part of the PICK gene, while lncRNA_3097.2 and lncRNA_3129.5 overlapped intronic part of the genes GADL1 and PSMD6. The lncRNA associated with PICK1, GADL1, and PMD6 genes were enriched in the pathways associated with the ionotropic glutamate receptor, gamma‐aminobutyric acid synthesis, and the ubiquitin–proteasome pathway. For marbling, 50 lncRNA were DE (p‐value ≤ 0.01) in high marbling group compared with low marbling animals. The genic lncRNAs, such as lncRNA_3191.1, were overlapped exonic part of the ITGAL gene, and the lncRNA_512.1, lncRNA_3721.1, and lncRNA_41.4 overlapped intronic parts of the KRAS and MASP1 genes. The KRAS and ITGAL genes were enriched in pathways associated with integrin signaling, which is involved in intracellular signals in response to the extracellular matrix, including cell form, mobility, and mediates progression through the cell cycle. In addition, the lincRNAs identified to marbling trait were associated with several genes related to calcium binding, muscle hypertrophy, skeletal muscle, lipase, and oxidative stress response pathways that seem to play a role important in the physiological processes related to meat quality. These findings bring new insights to better understand the biology mechanisms involved in the gene regulation of these traits, which will be valuable for a further investigation of the interactions between lncRNA and mRNAs, and of how these interactions may affect meat quality traits.

Comparison of two live-animal ultrasound systems for genetic evaluation of carcass traits in Angus cattle.

The improvement of carcass traits is an important breeding objective in beef cattle breeding programs. The most common way of selecting for improvement in carcass traits is via indirect selection using ultrasound scanning of selection candidates which are submitted to genetic evaluation programs. Two systems used to analyze ultrasound images to predict carcass traits are the Pie Medical Esaote Aquila (PIE) and Central Ultrasound Processing (CUP). This study compared the ability of the two systems to predict carcass traits for genetic evaluation in Australian Angus cattle. Genetic and phenotypic parameters were estimated using data from 1,648 Angus steers which were ultrasound scanned twice with both systems, first at feedlot entry and then following 100 d in the feedlot. The traits interpreted from ultrasound scanning included eye muscle area (EMA), rib fat (RIB) rump fat (RUMP), and intramuscular fat (IMF). Abattoir carcass data were collected on all steers following the full feedlot feeding period of 285 d. For all ultrasound scan traits, CUP resulted in higher phenotypic and genetic variances compared to the PIE. For IMF, CUP had higher heritability at feedlot intake (0.51 for CUP compared to 0.37 for PIE) and after 100 d feeding (0.54 for CUP compared to 0.45 PIE). CUP predicted IMF also tended to have stronger correlations with the breeding objective traits of carcass IMF and marbling traits, both genetically (ranging from 0.59 to 0.75 for CUP compared to 0.45–0.63 for PIE) and phenotypically (ranging from 0.27 to 0.43 for CUP compared to 0.19–0.28 for PIE). Ultrasound scan EMA was the only group of traits in which the heritabilities were higher for PIE (0.52 for PIE compared to 0.40 for CUP at feedlot intake and 0.46 for PIE compared to 0.43 for CUP at 100 d of feeding), however with similar relationships to the breeding objective carcass EMA observed. For subcutaneous fat traits of ultrasound RIB and RUMP, the heritabilites and genetic correlations to the related carcass traits were similar, with the exception being the higher heritability observed for CUP predicted RUMP at feedlot intake at 0.52 compared to 0.38 for PIE. The results from this study indicates that the CUP system, compared to PIE, provides an advantage for genetic evaluation of carcass traits in Angus cattle, particularly for the IMF and associated marbling traits.

Prediction of consumer palatability in beef using visual marbling scores and chemical intramuscular fat percentage

With development of objective technologies that can predict chemical intramuscular fat percentage (IMF%), there is a need to understand the relationships between existing marbling traits, IMF% and eating quality. This study utilised historical carcass data (n = 9641 observations) from the Meat Standards Australia (MSA) industry research dataset and included MSA grading data, chemical IMF% data and weighted composite eating quality scores (MQ4). Several analyses were performed to assess the prediction of MQ4 by MSA marbling, M. longissimus thoracis et lumborum (striploin) IMF% and cut specific IMF%. Results demonstrated that there was similar precision between chemical IMF% (R2 = 0.32, RSE = 11.8) and MSA marbling (R2 = 0.28, RSE = 11.9) in the prediction of grilled 14 day aged striploin MQ4, with similar results across other cut by cook by days aged combinations. These results support the development of objective technologies that predict chemical IMF% in parallel with MSA marbling for carcass grading and the prediction of eating quality.

Promoter CpG methylation status affects ADRP gene expression level and intramuscular fat content in pigs

Adipose differentiation-related protein (ADRP) is a lipid droplet-associated protein that is expressed early during adipose differentiation. However, the underlying mechanism is still unclear. In this study, the porcine ADRP (pADRP) gene regulatory mechanism and its relationship to intramuscular fat (IMF) content are analysed. We investigated the characteristics of the pADRP gene prompter as well as its transcription level, core promoter and epigenetic modification status using real-time PCR, Dual-luciferase reporter assays and bisulphite sequencing. The results showed that pADRP mRNA expression in Longissimus Dorsi (LD) muscle of the low IMF (LEAN) group was lower than that in the high IMF (FAT) group (p<.01). Maximum promoter activity was found in the −926 bp to −235 bp region. The methylation level of the pADRP of this region (mainly 7th, 10th, 12th CpG sites) in the low IMF group (86.67%) was significantly higher than that in the high IMF group (46.7%) (p<.01). Our result plays an important role in pADRP transcriptional regulation and provides a good prospect for the marbling traits improvement. Highlights pADRP expression differs in divergent IMF content pigs. Promoter region located −929 to −235 bp, and its methylation contributes to gene expression.

Genome wide association and gene enrichment analysis reveal membrane anchoring and structural proteins associated with meat quality in beef

BackgroundMeat quality related phenotypes are difficult and expensive to measure and predict but are ideal candidates for genomic selection if genetic markers that account for a worthwhile proportion of the phenotypic variation can be identified. The objectives of this study were: 1) to perform genome wide association analyses for Warner-Bratzler Shear Force (WBSF), marbling, cooking loss, tenderness, juiciness, connective tissue and flavor; 2) to determine enriched pathways present in each genome wide association analysis; and 3) to identify potential candidate genes with multiple quantitative trait loci (QTL) associated with meat quality.ResultsThe WBSF, marbling and cooking loss traits were measured in longissimus dorsi muscle from 672 steers. Out of these, 495 animals were used to measure tenderness, juiciness, connective tissue and flavor by a sensory panel. All animals were genotyped for 221,077 markers and included in a genome wide association analysis. A total number of 68 genomic regions covering 52 genes were identified using the whole genome association approach; 48% of these genes encode transmembrane proteins or membrane associated molecules. Two enrichment analysis were performed: a tissue restricted gene enrichment applying a correlation analysis between raw associated single nucleotide polymorphisms (SNPs) by trait, and a functional classification analysis performed using the DAVID Bioinformatic Resources 6.8 server. The tissue restricted gene enrichment approach identified eleven pathways including “Endoplasmic reticulum membrane” that influenced multiple traits simultaneously. The DAVID functional classification analysis uncovered eleven clusters related to transmembrane or structural proteins. A gene network was constructed where the number of raw associated uncorrelated SNPs for each gene across all traits was used as a weight. A multiple SNP association analysis was performed for the top five most connected genes in the gene-trait network. The gene network identified the EVC2, ANXA10 and PKHD1 genes as potentially harboring multiple QTLs. Polymorphisms identified in structural proteins can modulate two different processes with direct effect on meat quality: in vivo myocyte cytoskeletal organization and postmortem proteolysis.ConclusionThe main result from the present analysis is the uncovering of several candidate genes associated with meat quality that have structural function in the skeletal muscle.

Transcriptome analysis to characterize genes related to the marbling trait on meat quality of Aberdeen Angus

Transcriptome analysis to characterize genes related to the marbling trait on meat quality of Aberdeen Angus

Comparison of Marbling Fleck Characteristics and Objective Tenderness Parameters with Different Marbling Coarseness within Longissimus thoracis Muscle of High-marbled Hanwoo Steer.

It is important to understand how marbling traits and tenderness differ among beef steaks from the carcass grading site and other regions within the longissimus thoracis (LT) muscle, as these characteristics are closely associated with consumer acceptability and willingness to purchase. Thus, the aim of this study was to compare the marbling fleck traits and objective tenderness parameters in the groups classified by the coarseness index (CI) of marbling fleck (high and low groups) at the carcass grading site (13th thoracic vertebra; 13T) and three different locations (13T, 9T, and 6T) within the LT muscle from well-marbled (marbling score 7 to 9) Hanwoo steer. Image analysis showed that the longitudinal locations had a significant effect on marbling fleck traits. The total area of large marbling fleck divided by the total marbling area (coarseness) was higher at the central region (13T to 12T) compared to the front thoracic region (6T to 5T) in the high CI group (0.23 vs. 0.17, p<0.05), whereas no significant differences were observed in the total number of marbling fleck within the LT muscle in the high or low CI groups (p>0.05). Location effect on objective tenderness parameters within the LT muscle was somewhat limited, although the high CI group had a lower Warner-Bratzler shear force (WBS) value than did the low group (p<0.05). Taken together, the degree of coarseness of marbling fleck decreased from the carcass grading site to the front thoracic site, whereas the objective tenderness parameters, including WBS and hardness, of the grading site did not differ from the other regions within the LT muscle.

X-Ray computed tomography evaluation of intramuscular fat content in Hungarian simmental cattle

Intramuscular fat content (marbling) is an economically important factor in many beef carcass classification systems. The aim of this study was to evaluate marbling of longissimus muscle with different methods (USDA marbling score, image analysis of X-ray computed tomography scans, and conventional method), moreover it was aimed to establish the relationship between marbling traits and SEUROP conformation and fat score. Bulls (n=46) were slaughtered at an average weight of 536±126 kg and an average age of 646±437 days. The average growth rate of bulls was 955 g day–1, the average chemical fat content of longissimus varied between 2.3 to 5.0% in fat classes. The intramuscular fat content on CT-scans closely correlated with chemical fat content (r=0.9). The highest frequency of USDA marbling score was “small” (55.2%), followed by “slight” (25.5%), “modest” (17%), and “moderate” (2.1%). Bulls with higher growth rate had lower CT-measured marbling traits in longissimus muscle (r = –0.4 – –0.5). The CT scans of longissimus muscle can be used for the evaluation of marbling in Hungarian Simmental cattle. The SEUROP conformation and fat score have no relationship with marbling traits.

Evaluation of marbling traits by X-ray computed tomography in Hungarian Simmental bulls

Marbling is an economically important factor in many beef carcass grading schemes. This study aimed to evaluate marbling traits of longissimus thoracis muscle (LT) with different methods: USDA marbling score, intramuscular fat (IMF) content by image analysis of X-ray computed tomography (CT) scans and by conventional analytical method. Bulls (n=46) were slaughtered at an average weight of 536 kg and an average age of 646 days. Mean values of EUROP fat scores varied from 2− to 2+, whereas mean values of EUROP conformation grade from O0 to R0. Average growth rate of bulls was 955 g/day. Average chemical fat content of LT varied from 2.2% to 3.1% across conformation classes, and from 2.3% to 5.0% across fat classes. Intramuscular fat content in the 12th rib and in LT on CT-scans closely correlated with chemical fat content (r=0.81 and 0.85, respectively). The highest frequency of USDA marbling score was ‘small’ (55.2%), followed by ‘slight’ (25.5%), ‘modest’ (17%) and ‘moderate’ (2.1%). Computed tomography scans of LT can be used for the evaluation of marbling in Hungarian Simmental cattle. Bulls with higher growth rate had lower marbling level in LT (r=−0.4 to −0.5). EUROP conformation and fat scores have no relationship with marbling traits in this specific cattle population.

Identification of microRNA and target gene associated with marbling score in Korean cattle (Hanwoo)

Marbling is a crucial characteristic in meat quality assessment. In the search for a genetic basis of meat quality, a large number of gene analyses seeking to find loci for a marbling trait have already been reported. However, the influence of microRNA (miRNA) on expression patterns and their ultimate influence on marbling is poorly understood. To better understand post-transcriptional influences on marbling, we applied a microarray analysis to measure the relationship between marbling scores and miRNA and messenger RNA expression in Hanwoo longissimus muscle tissue. Our results build correlations between miRNAs and differentially expressed genes and pathways. Our microarray analysis identified 763 genes and 11 miRNAs that are differentially expressed relative to marbling score. Overall, upregulated miRNAs were associated with downregulated genes. Fifteen genes targeted by miRNAs including insulin-like growth factor 1 (IGF-1) and kruppel-like factor 11 (KLF11), which regulate fatty acid synthase and lipid metabolism. And the expression levels of KLF11 and bta-miR-494 were validated. The results show that downregulated bta-miR-494 was associated with the upregulation of KLF11 gene. Among the differentially expressed genes found to be associated with the marbling score, we identified 15 genes targeted by miRNAs. Furthermore, the expression patterns of the genes KLF11, and bta-miR-494, may influence marbling in Hanwoo.

Allele Frequency Distribution of the &amp;lt;i&amp;gt;NCAPG c&amp;lt;/i&amp;gt;.1326&amp;lt;i&amp;gt;T&amp;lt;/i&amp;gt;&amp;gt;&amp;lt;i&amp;gt;G&amp;lt;/i&amp;gt; SNP Associated with Growth-Related Traits in Niigata Population of Japanese Black Beef Cattle

Growth performance as well as marbling is the main breeding objectives in Japanese Black cattle, the major beef breed in Japan. A previous study has identified the c.1326T>G single nucleotide polymorphism (SNP) in the NCAPG (non-SMC condensin I complex, subunit G) gene that leads to the amino acid change p.Ile442Met in the NCAPG protein, which is a candidate causative variation for a bovine carcass weight (CWT) quantitative trait locus (QTL). In this study, we first confirmed the association of the c.1326T>G SNP with the growth-related traits, CWT, rib eye area (REA) and rib thickness (RT), and showed significant effect of the SNP genotypes on the marbling trait, beef marbling score (BMS), in the Japanese Black beef cattle population of the Niigata prefecture, with the G allele being associated with a favorable phenotype of these traits. Thus, we concluded that the c.1326T>G SNP is useful for effective marker-assisted selection to increase meat quality and meat productivity in Japanese Black beef cattle of the Niigata prefecture. Furthermore the frequency of the favorable G allele of the c.1326T>G SNP in the Niigata prefecture population was significantly lower than the frequency of this allele in Japanese Black cattle population of the Kagoshima prefecture. However, no statistically significant difference was detected between the allele frequencies estimated by maternal alleles in the half-sib progeny steers in the Niigata prefecture population and obtained in Japanese Black cattle population of the Kagoshima prefecture.

Association of the Expression Level of the MYBPC1 Gene in Skeletal Muscle With Marbling Trait in Japanese Black Beef Cattle

Abstract Marbling characterized by the amount and distribution of intramuscular fat (IMF) in longissimus muscle (LM) and measured as beef marbling score (BMS), is an economically important trait of beef cattle in Japan. The myosin binding protein C, slow type (MYBPC1) gene, involved in efficient energy metabolism and homeostasis during muscle contraction in slow skeletal muscle, has been previously shown to be expressed at different levels in the LM between high-marbled and lowmarbled steer groups using differential-display PCR (ddPCR). In this study, we found that IMF area (%) in the sacrococcygeus muscle (SM) was positively correlated with BMS in the LM in Japanese Black steers (n=22, r=0.941, P&lt;0.0001). This suggested that the IMF area (%) in the SM tends to equate marbling level in the LM. Furthermore, we showed that the MYBPC1 expression level in SM was significantly higher in the Japanese Black steers (n=5) with high BMS than in the Japanese Black steers (n=5) with low BMS (P&lt;0.001). Moreover, correlation analyses showed that the expression level of the MYBPC1 gene was positively correlated with IMF area (%) (n=22, r=0.858, P&lt;0.0001) and BMS (n=22, r=0.769, P&lt;0.0001), indicating the association of MYBPC1 expression level with marbling trait. These results, together with the previous ddPCR result, suggested that high level of MYBPC1 expression may be associated with the development of marbling in Japanese Black beef cattle.

Genetic diversity analysis of the thyroglobulin gene promoter in buffalo and other bovines

In total 937bp of the thyroglobulin (TG) gene, including promoter, exon1 and partial intron1 were characterized and compared across four livestock species, cattle, buffalo, yak and mithun. Identity was more than 98% and transcription factor binding sites analysis revealed the presence of variable numbers of potential binding sites in cattle, riverine buffalo, swamp buffalo, yak and mithun. The putative TTF-1 binding sites appeared to be conserved across all the investigated species except for a single C>T variation observed in TG promoter of Indicus cattle. A total of 15 polymorphic sites were observed in cattle and 8 in buffalo, out of which 2 were already reported in cattle and 4 polymorphic sites were common among cattle and buffaloes. The Principal component analysis results based on identified SNPs, revealed a close relationship between Crossbred and Indian Tharparkar breed of cattle as well as between Murrah and Banni breeds of buffalo. Analysis of the previously reported SNP, PsuI (g.−422C>T) marker (378C>T in our studies), associated with low marbling trait of meat in cattle, revealed an average frequency of 95% for the favourable C allele in Indian cattle, while it was fixed in the Indian swamp and riverine buffalo breeds. The study indicates, identification of genetic variation in the promoter region that could potentially affect the TG expression however, the association of the T allele with the fat deposition in Indian cattle and buffalo breeds needs to be verified.

Genetic dissection of marbling trait through integration of mapping and expression profiling

Marbling traits, defined by the amount of intramuscular fat, has a heritable component and are quantitative in nature, being influenced by many genes of variable individual effects. The identification of the genetic variation associated with marbling is an important step toward the improvement of beef quality through breeding programs and the understanding of the biological network of marbling. A lot of genomic studies based on functional candidate gene approach and quantitative trait locus (QTL) mapping and many transcriptome studies based on expression profiling, respectively, provide information on variation in genomic regions and individual genes associated with marbling and of genes with marbling-associated expression changes. Further, the integrative approach combining mapping and expression profiling data is proving useful for identifying the causal genes for marbling QTLs. Application of this integrative approach to our marbling study using a rat model, Otsuka Long-Evans Tokushima Fatty (OLETF) rat and Japanese Black beef cattle is introduced finally in this review.

Gene Co-expression Analysis to Characterize Genes Related to Marbling Trait in Hanwoo (Korean) Cattle.

Marbling (intramuscular fat) is an important trait that affects meat quality and is a casual factor determining the price of beef in the Korean beef market. It is a complex trait and has many biological pathways related to muscle and fat. There is a need to identify functional modules or genes related to marbling traits and investigate their relationships through a weighted gene co-expression network analysis based on the system level. Therefore, we investigated the co-expression relationships of genes related to the ‘marbling score’ trait and systemically analyzed the network topology in Hanwoo (Korean cattle). As a result, we determined 3 modules (gene groups) that showed statistically significant results for marbling score. In particular, one module (denoted as red) has a statistically significant result for marbling score (p = 0.008) and intramuscular fat (p = 0.02) and water capacity (p = 0.006). From functional enrichment and relationship analysis of the red module, the pathway hub genes (IL6, CHRNE, RB1, INHBA and NPPA) have a direct interaction relationship and share the biological functions related to fat or muscle, such as adipogenesis or muscle growth. This is the first gene network study with m.logissimus in Hanwoo to observe co-expression patterns in divergent marbling phenotypes. It may provide insights into the functional mechanisms of the marbling trait.

Meat quality traits and muscle composition of cows differing in lactation performance

Abstract. Beef and dairy cows differ in the way in which they utilise nutrients and in accretion or mobilisation of body reserves during lactation. Thus far, little is known about the impact of lactation performance on body composition, meat quality, and the related muscle structure of cows with a defined, combined beef and dairy genetic background. In the described experiment, 50 F2 cows, originating from mating Charolais bulls to German Holstein cows and a following intercross of F1 individuals, were slaughtered during the second lactation, 30 days after calving. Cows were assigned to 3 groups, each containing representatives of 3 families, according to lactation performance. Standard carcass and meat quality traits were determined. Additionally, samples from longissimus muscle were investigated by histology and computer image analysis for muscle fibre profile, intramuscular fat cell size, and marbling traits. Subcutaneous fat cell size was measured to estimate the impact of lactation on body fat reserves. The results suggest no influence of the duration of the first lactation on body composition, meat quality or muscle structure. However, the amount of milk per day influenced body weight, body composition, and marbling traits. Relationships between traits were low, but showed consistently that increasing milk yield was negatively correlated with tissue accretion. Changes of muscle fibre and fat cell profile, indicating protein or fat mobilisation by lactation, could not be detected. In the presented study, lactation had only minor consequences for meat quality.

Identification of Candidate Genes Associated with Beef Marbling Using QTL and Pathway Analysis in Hanwoo (Korean Cattle).

Marbling from intramuscular fat is an important trait of meat quality and has an economic benefit for the beef industry. Quantitative trait loci (QTL) fine mapping was performed to identify the marbling trait in 266 Hanwoo steers using a 10K single nucleotide polymorphism panel with the combined linkage and linkage disequilibrium method. As a result, we found nine putative QTL regions for marbling: three on BTA6, two on BTA17, two on BTA22, and two on BTA29. We detected candidate genes for marbling within 1 cM of either side of the putative QTL regions. Additionally, to understand the functions of these candidate genes at the molecular level, we conducted a functional categorization using gene ontology and pathway analyses for those genes involved in lipid metabolism or fat deposition. In these putative QTL regions, we found 95 candidate genes for marbling. Using these candidate genes, we found five genes that had a direct interaction with the candidate genes. We also found SCARB1 as a putative candidate gene for marbling that involves fat deposition related to cholesterol transport.