How Muscle Structure and Composition Influence Meat and Flesh Quality

Age-Dependent Expression of MyHC Isoforms and Lipid Metabolism-Related Genes in the Longissimus Dorsi Muscle of Wild and Domestic Pigs

This study aimed to compare age-dependent changes in the relative expression of genes encoding myosin heavy chain (MyHC) isoforms and selected lipid metabolism-related genes in the longissimus dorsi muscle of wild pigs (WPs) and domestic pigs (DPs). Muscles sampled from postnatal day one as well as three-week-old and two-year-old animals were used in quantitative polymerase chain reaction (qPCR) assays, histological evaluations of succinate dehydrogenase (SDH) activity, and intra-myofiber lipid (IMFL) assessment. Expression of the MyHC isoforms displayed the most extensive age- and breed-dependent changes within the first three postnatal weeks. The MyHC_embry level decreased significantly faster in the WPs than in the DPs. The relative MyHC-I and -IIa expression was significantly higher in the WPs, and MyHC-IIb was substantially higher in the DPs. The differences in MyHC expression corroborated the number of SDH-positive myofibers and IMFLs. Expression of the peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α), peroxisome proliferator-activated receptor gamma (PPARγ) and lipoprotein lipase (LPL) genes displayed only age-related variations. In summary, the evidence is provided for accelerated postnatal myofiber transformation directed towards oxidative myofibers in WPs. The SDH activity/staining intensity largely reflected the expression of MyHCs, and not genes involved in lipid uptake and utilization.

The first comprehensive description of the expression profile of genes involved in differential body growth and the immune system of the Jeju Native Pig and miniature pig

Sus scrofa provides a major source of animal protein for humans as well as being an excellent biomedical model. This study was carried out to understand, in detail, the genetic and functional variants of Jeju Native Pigs and miniature pigs through differential expression profiling of the genes controlling their immune response, growth performance, and meat quality. The Illumina HiSeq 2000 platform was used for generating 1.3 billion 90 bp paired-end reads, which were mapped to the S. scrofa genome using TopHat2. A total of 2481 and 2768 genes were differentially expressed with 8-log changes in muscle and liver samples, respectively. Five hundred forty-eight genes in muscle and 642 genes in liver samples had BLAST matches within the non-redundant database. GO process and pathway analyses showed enhanced biological processes related to the extracellular structural organization and skeletal muscle cell differentiation in muscle tissue, whereas the liver tissue shares functions related to the inflammatory response. Herein, we identify inflammatory regulatory genes in miniature pigs and growth response genes in Jeju Native Pigs, information which can provide a stronger base for the selection of breeding stock and facilitate further in vitro and in vivo studies for therapeutic purposes.

Methods for Extraction of Muscle Proteins from Meat and Fish Using Denaturing and Nondenaturing Solutions

The objective of the present study was to test two extraction methods including solutions with different ionic strengths on the extraction and separation of the myofibrillar proteins from meat and fish muscles of different species. Meat samples from longissimus thoracis muscle of beef and lamb, pectoralis major muscle of chicken, and dorsal white muscle of fish from sole (Solea solea), European hake (Merluccius merluccius), and sea bass (Dicentrarchus labrax) were analyzed. The extraction method using nondenaturing solution led to a major extraction of high molecular-weight proteins as myosin heavy chain, α-actinin, and desmin; on the contrary, the denaturing method provided a good protein extractability of proteins and fragments with low molecular-weight as actin, troponin-T, tropomyosin, and myosin light chain 1 and 2 proteins for the most meat and fish samples. The nondenaturing extraction method showed several advantages resulting in time and labour saving and in minimizing the use of toxic and polluting agents.

Metabolomics investigation of dietary effects on flesh quality in grass carp (Ctenopharyngodon idellus)

Background

The ultrahigh density intensive farming model of grass carp (Ctenopharyngodon idellus) may elicit growth inhibition, decrease flesh quality, and increase disease susceptibility of fish. The degradation in quality and excessive fat accumulation in cultured C. idellus have long been attributed to possible alterations in the lipid metabolism of fish muscle tissues as a result of overnutrition from artificial diets. To investigate the effects of different diets on fish muscle quality, a large-scale metabolomics study was performed on 250 tails of C. idellus.

Findings

The experimental fish were divided into four groups based on sex and diet—female artificial feed (FAF), female grass feed, male artificial feed (MAF), and male grass feed (MGF). After a 113-day rearing period, the artificial feed (AF) group showed a significantly higher total mass of muscle fat (P < 0.01), with the FAF group being the highest. Metabolomics profiling based on liquid chromatography-mass spectrometry revealed distinctive patterns of clustering according to the four groups. Overall, artificial feeding was associated with higher concentrations of docosapentaenoic acid, dihomo-gamma-linolenic acid, and arachidonic acid, whereas grass feeding was associated with elevated n-3 unsaturated fatty acids (UFAs) such as eicosapentaenoic acid, alpha-linolenic acid, and gamma-linolenic acid. Artificial feeding also resulted in significant increased docosahexaenoic acid in MAF muscle than in MGF fish, whereas there was no significance in the comparison of female samples. Metabolic pathway analyses using both targeted and untargeted approaches consistently revealed that arachidonic acid metabolism and steroid hormone biosynthesis pathways were significantly different between AF and grass fed groups.

Conclusions

Our results suggest that grass is a better source of dietary fatty acid and protein when compared to artificial feed. Grass feeding could effectively lower triglycerides in serum, reduce fat accumulation, and alter lipid compositions in fish muscle by increasing the concentrations of n-3 UFAs, leading to better nutrition and health.

Ectopic Overexpression of Porcine Myh1 Increased in Slow Muscle Fibers and Enhanced Endurance Exercise in Transgenic Mice

Myosin heavy chain (MyHC) isoforms consist of Myh7, Myh2, Myh1, and Myh4, which are expressed in skeletal muscle tissues during postnatal development. These genes influence the contraction–relaxation activity in skeletal muscles and are involved in determining muscle composition such as the proportion of fast-to-slow and/or slow-to-fast fiber types. Among them, Myh1 is associated with skeletal muscle contraction and is involved in both slow-to-fast and fast-to-slow transition. However, the muscle transition mechanism is not well understood. For this study, we first produced porcine Myh1 transgenic (TG) mice to study whether the ectopic expressed porcine Myh1 gene had any effects on muscle composition, especially on slow-type muscle components. Our results showed that the factors associated with slow muscles, such as Myh7, Myoglobin, Troponin (slow-type units), and cytochrome C, were highly expressed in the quadriceps muscles of Myh1 transgenic mice. Furthermore, the ectopic porcine MYH1 protein was located only in the slow-type muscle fibers of the quadriceps muscles in Myh1 transgenic mice. In physical endurance tests, Myh1 transgenic mice ran longer and further on a treadmill than wild-type (WT) mice. These data fully supported our hypothesis that Myh1 is associated with slow muscle composition, with overexpression of Myh1 in muscle tissues possibly being a new key in modulating muscle fiber types. Our study provides a better understanding of muscle composition metabolism, physical mobility, and genetic factors in muscle fatigue.

Mechanical texture profile of Hanwoo muscles as a function of heating temperatures

Background

Cooking temperature and consequently doneness of beef muscles are most important for the palatability and consumer acceptability. Current study assessed the response of mechanical texture of Hanwoo muscles as a function of cooking temperature at different ageing days. Six muscles (Psoas major (PM), Longissimus thoracics (LT), Gluteus medius (GM), Semimembranosus (SM), Biceps femoris (BF) and Triceps brachii (TB)) were collected from each 10 Hanwoo steers. Warner-Bratzler WB-shear force (WBSF) and texture profile analysis (TPA) texture profiles were determined after 3 or 21 days of chiller, and randomly assigned to four groups; non-cooked, cooked at 55, 70 or 85 °C.

Results

Toughness of WBSF and TPA hardness of Hanwoo muscles were presence in the order of LT = PM = GM = SM < BF = TB (p < 0.001) for non-cooked raw muscle, and PM < LT = GM = SM < TB=BF (p < 0.001) for cooked meat aged for 3 days. WBSF linearly increased in 3 days aged meats after cooked at a higher temperature (P < 0.05). On the other hand, toughening of the muscles were significantly (P < 0.05) differed at various temperature when muscles were aged for 21 days. WBSF of PM and LT muscles were significantly increased at a higher cooking temperature, while other muscles (i.e., GM, SM, BF, TB) showed the lowest values at 70 °C. In the case of TPA hardness, the effect of cooking temperature was very less in the toughness of the muscle (P > 0.05).

Conclusion

Taken together, these findings clearly showed that the toughness of the muscle highly depends and varies upon the temperature and ageing of the muscle. Moreover, the effect of cooking temperature was very limited on aged muscles. The results mirror the importance of cooking temperature for objective measurements which ultimately estimate sensory tenderness and other quality traits.

Effect of Freezing on the Shelf Life of Salmon

Food shelf-life extension is important not only to food manufacturers, but also to home refrigeration/freezing appliance companies, whose products affect food quality and food waste. While freezing and refrigerating both extend the shelf life of foods, food quality deterioration continues regardless of the preservation method. This review article discusses the global fish market, the composition of fish meat, and the effects of freezing and thawing on salmon quality.

Physicochemical and sensory characterization of three different portions from commercial pirarucu (Arapaima gigas) fillets

Abstract The objective of the present study was to investigate the relevant physicochemical and sensory parameters of three different Arapaima gigas muscle portions. Cranial, medial and caudal portions were analysed regarding their proximate compositions, instrumental colour and texture parameters, and sensory evaluations. The medial and caudal portions exhibited the greatest (P < 0.05) lipid contents and energy values and the lowest (P < 0.05) moisture and carbohydrate levels. The protein contents were similar (P > 0.05) for the different muscle portions. Before cooking, the medial and caudal portions displayed the greatest (P < 0.05) values for lightness, redness, hardness and chewiness. After cooking, no differences ( P > 0.05) were observed between the different muscle portions for the instrumental colour parameters, while the medial portion exhibited lower (P < 0.05) values for hardness and chewiness as compared to the caudal portion. The cranial portion received the lowest (P < 0.05) scores for flavour and overall liking. Thus the Arapaima gigas medial and caudal muscle portions presented the greatest potentials to satisfy the consumer requirements.

Identification of putative regulatory regions and transcription factors associated with intramuscular fat content traits

Background

Integration of high throughput DNA genotyping and RNA-sequencing data allows for the identification of genomic regions that control gene expression, known as expression quantitative trait loci (eQTL), on a whole genome scale. Intramuscular fat (IMF) content and carcass composition play important roles in metabolic and physiological processes in mammals because they influence insulin sensitivity and consequently prevalence of metabolic diseases such as obesity and type 2 diabetes. However, limited information is available on the genetic variants and mechanisms associated with IMF deposition in mammals. Thus, our hypothesis was that eQTL analyses could identify putative regulatory regions and transcription factors (TFs) associated with intramuscular fat (IMF) content traits.

Results

We performed an integrative eQTL study in skeletal muscle to identify putative regulatory regions and factors associated with intramuscular fat content traits. Data obtained from skeletal muscle samples of 192 animals was used for association analysis between 461,466 SNPs and the transcription level of 11,808 genes. This yielded 1268 cis- and 10,334 trans-eQTLs, among which we identified nine hotspot regions that each affected the expression of > 119 genes. These putative regulatory regions overlapped with previously identified QTLs for IMF content. Three of the hotspots respectively harbored the transcription factors USF1, EGR4 and RUNX1T1, which are known to play important roles in lipid metabolism. From co-expression network analysis, we further identified modules significantly correlated with IMF content and associated with relevant processes such as fatty acid metabolism, carbohydrate metabolism and lipid metabolism.

Conclusion

This study provides novel insights into the link between genotype and IMF content as evident from the expression level. It thereby identifies genomic regions of particular importance and associated regulatory factors. These new findings provide new knowledge about the biological processes associated with genetic variants and mechanisms associated with IMF deposition in mammals.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4871-y) contains supplementary material, which is available to authorized users.

Effect of Meat Type, Animal Fatty Acid Composition, and Isothermal Temperature on the Viscoelastic Properties of Meat Batters

The aim of this research was to simultaneously study the effect of meat type (chicken breast and leg meat), animal fatty acid composition (selected pork backfats having a low and high degree of saturation, respectively), and isothermal temperature (50, 60, 70, and 80 °C) on the viscoelastic properties of meat batters during and after application of different time-temperature profiles. Gelation of meat proteins contributed most to the viscoelastic properties of meat batters during heating, whereas crystallization of the lipids especially contributed to the viscoelastic properties during the cooling phase. Although the meat type had little effect on the final viscoelastic properties of the meat product, the fatty acid composition had a clear impact on the melting peak area (and therefore solid fat content) of lard, and subsequently on the final viscoelastic properties of meat batters prepared with different types of fats, with higher G' (elastic modulus) values for the most saturated animal fat. The crystallization of the fat clearly transcended the effect of the meat type with regard to G' at the end of the process. With increasing (isothermal) temperature, G' of meat batters increased. Therefore, it could be concluded that the structural properties of heated meat batters mainly depend on the heating temperature and the fatty acid composition, rather than the meat type.

PRACTICAL APPLICATION

Quality characteristics of cooked sausages depend on multiple factors such as the meat and fat type, non-meat ingredients and processing conditions. From this study it could be concluded that the structural properties of cooked sausage batters mainly depend on the heating temperature and the fatty acid composition, rather than the meat type. Because the fatty acid composition of different animal fats differs widely, these results may be a concern for all manufactures of cooked sausages products with regard to the product structure and final texture, keeping in mind that rendered fat was used in this study, which is not common in sausage making.

Effects of trypsinization and of a combined trypsin, collagenase, and DNase digestion on liberation and in vitro function of satellite cells isolated from juvenile porcine muscles

Muscle stem cells, termed satellite cells (SC), and SC-derived myogenic progenitor cells (MPC) are involved in postnatal muscle growth, regeneration, and muscle adaptability. They can be released from their natural environment by mechanical disruption and tissue digestion. The literature contains several isolation protocols for porcine SC/MPC including various digestion procedures, but comparative studies are missing. In this report, classic trypsinization and a more complex trypsin, collagenase, and DNase (TCD) digestion were performed with skeletal muscle tissue from 4- to 5-d-old piglets. The two digestion procedures were compared regarding cell yield, viability, myogenic purity, and in vitro cell function. The TCD digestion tended to result in higher cell yields than digestion with solely trypsin (statistical trend p = 0.096), whereas cell size and viability did not differ. Isolated myogenic cells from both digestion procedures showed comparable proliferation rates, expressed the myogenic marker Desmin, and initiated myogenic differentiation in vitro at similar levels. Thus, TCD digestion tended to liberate slightly more cells without changes in the tested in vitro properties of the isolated cells. Both procedures are adequate for the isolation of SC/MPC from juvenile porcine muscles but the developmental state of the animal should always be considered.

Meat quality traits in the Greater rhea (Rhea americana) as influenced by muscle, sex and age

Meat from the Greater rhea (Rhea americana) could compete with traditional red meats, diversifying the market of protein products of animal origin. The meat from 32 rheas was used to study quality aspects and this included ultimate pH (pHu), color, water-holding capacity (WHC%), cooking loss (CL%) and tenderness. The muscles sampled were the Gastrocnemius pars externa, Iliofibularis and Obturatorius medialis from both sexes at multiple ages (10, 12, 14, 16 months). Age at slaughter affected WHC%, CL%, and color in raw meat and tenderness in cooked meat. Muscles under study showed differences in terms of pHu, raw meat color, and tenderness of cooked meat. Sex did not have a significant effect on any of the variables studied. According to our results, rhea meat from younger animals, between 10 to 14 months old, was tender and moderately juicy and the visual color was appreciated by the consumers.

Diet Affects Muscle Quality and Growth Traits of Grass Carp (Ctenopharyngodon idellus): A Comparison Between Grass and Artificial Feed

Fish muscle, the main edible parts with high protein level and low fat level, is consumed worldwide. Diet contributes greatly to fish growth performance and muscle quality. In order to elucidate the correlation between diet and muscle quality, the same batch of juvenile grass carp (Ctenopharyngodon idellus) were divided into two groups and fed with either grass (Lolium perenne, Euphrasia pectinata and Sorghum sudanense) or artificial feed, respectively. However, the different two diets didn't result in significant differences in all the detected water quality parameters (e.g., Tm, pH, DO, NH3/[Formula: see text]-N, [Formula: see text]-N, [Formula: see text], TN, TP, and TOC) between the two experimental groups. After a 4-month culture period, various indexes and expression of myogenic regulatory factor (MRFs) and their related genes were tested. The weight gain of the fish fed with artificial feed (AFG) was nearly 40% higher than the fish fed with grass (GFG). Significantly higher alkaline phosphatase, total cholestrol, high density cholestrol and total protein were detected in GFG as compared to AFG. GFG also showed increased hardness, resilience and shear force in texture profile analysis, with significantly bigger and compact muscle fibers in histologic slices. The fat accumulation was most serious in the abdomen muscle of AFG. Additionally, the expression levels of MyoG, MyoD, IGF-1, and MSTNs were higher, whereas Myf-5, MRF4, and IGF-2 were lower in most positional muscles of GFG as compared to AFG. Overall, these results suggested that feeding grass could promote muscle growth and development by stimulating muscle fiber hypertrophy, as well as significantly enhance the expression of CoL1As. Feeding C. idellus with grass could also improve flesh quality by improving muscle characteristics, enhancing the production of collagen, meanthile, reducing fat accumulation and moisture in muscle, but at the cost of a slower growth.

Study on the transcriptional regulatory mechanism of the MyoD1 gene in Guanling bovine

The MyoD1 gene plays a key role in regulating the myoblast differentiation process in the early stage of skeletal muscle development. To understand the functional elements of the promoter region and transcriptional regulation of the bovine MyoD1 gene, we cloned eight fragments from the sequence region of the MyoD1 gene promoter and inserted them into eukaryotic expression vectors for cotransfection with the mouse myoblast cell line C2C12 and Madin-Darby bovine kidney (MDBK) line. A variety of transcription factor binding sites in the longest 5'-flanking fragment from Guanling cattle MyoD1-P1 were predicted by using the online software TFSEARCH and ALGGEN PROMO as well as validated by the promoter-binding TF profiling assay II and yeast one-hybrid (Y1H) assay, including MyoD, VDR, MEF1, MEF2, SF1, and Myf6. Myf6 strongly activated the MyoD1 promoter, while MyoD1 was also capable of efficiently activating the expression of its own promoter. The transcription factors MEF2A, SF1, and VDR were further confirmed to be capable of binding to MyoD1 by Y1H system experiments. The effects of the Guanling cattle MyoD1 gene on the mRNA expression of the MEF2A, SF1, and VDR genes were determined by using a lentivirus-mediated overexpression technique, confirming that overexpression of the MyoD1 gene upregulated the mRNA expression of MEF2A as well as downregulated the expression of SF1 and VDR in the process of muscle myogenesis. Our study revealed the effects of transcription factors including MEF2A, SF1 and VDR on regulatory aspects of MyoD1, providing abundant information for transcriptional regulation of MyoD1 in muscle differentiation.

Comparisons of meat quality and muscle fibre characteristics on multiple pig breeds and sexes using principal component analysis

Comprehensive understanding of the effect of pig breed and sex on meat quality and post-mortem muscle conditions will be necessary to estimate meat quality post mortem. In this study, we applied multiple regression and principal component analysis (PCA) using conventional meat quality traits and muscle fibre characteristics on six pig breeds and different sexes. A total of 1374 pigs from six breeds [Berkshire, Duroc, Landrace, Meishan, Yorkshire, and LYD (Landrace × Yorkshire sows with Duroc as terminal sires) crossbreed] belonging to three sexes (male, castrated male and female) were used in this study. Most of the muscle fibre characteristics showed moderate to high significant correlations with conventional meat quality traits. In particularly, the cross-sectional area (CSAF) of muscle fibres was strongly correlated with muscle pH values, water-holding capacity values and lightness (0.10 < |r| <0.26 and P < 0.01). Multiple regression analysis by general linear model revealed that the effects of breed were significant on muscle pH24h, lightness, drip loss, and marbling score (P < 0.01), whereas sex had no significant effect on meat quality. In the muscle fibre characteristics, the effects of breed and sex were significant on composition of area and density of muscle fibres (P < 0.05). We observed that the Meishan breed was clearly inferior to other breeds, whereas the LYD or Berkshire breeds showed better meat quality and muscle fibre properties. Moreover, we observed clear separations between pig breeds based on the PCA, whereas the sexes in each breed presented a continuum cluster. In summary, we suggest that muscle pH24h, lightness, and drip loss are conventional meat quality traits that can be considered as quantitative factors important in estimating ultimate meat quality of pigs along with the CSAF of muscle fibres; we conclude that Meishan pigs have low meat quality, whereas Berkshire and LYD crossbred pigs have higher quality of pork.

Effects of maternal parity on the pork quality traits of progeny

This study aimed to identify the influence of sow parity on the meat quality of progeny. A total of 656 progeny from 196 sows were categorised into three different groups based on parity: stage 1 (gilt), 2 (second to fourth parities), and 3 (over fifth parity). According to the significant differences between the parity stage groups in the multiple meat quality properties (P < 0.05), the parity stage 1 had higher muscle pH and lower drip loss in meat quality traits and showed smaller area composition of type IIb muscle fibres in muscle fibre characteristics than the other older groups. Moreover, the parity stage 1 group had significantly higher springiness, adhesiveness and chewiness (P < 0.001), whereas the stage 3 group showed relatively lower cohesiveness (P < 0.05) in the meat texture properties. The principal component analysis displayed more distance between stage 1 and other two groups than the distance between stage 2 and 3. Therefore, we suggest that maternal parity may affect pork quality in progeny and the younger stage group could have better meat quality than the older group.

Gene Effects on Body Weight, Carcass Yield, and Meat Quality of Thai Indigenous Chicken

The selection of rapidly growing animals in breeding programs has had inadvertent detrimental effects on meat quality. Thus, the aim of the present study was to investigate the relationship between body weight (BW) and meat quality traits, and the effects of genes encoding insulin-like growth factor I (IGF-I), insulin-like growth factor II (IGF-II), melanocortin-4 receptor (MC4R), and calpain 1 (CAPN1) on BW, carcass yield, and meat quality of the Thai indigenous chicken, Leung Hang Khao. Five hundred and ten chickens were used for genotyping. PCR-restriction fragment length polymorphism and PCR-single strand conformation polymorphism were used to determine the genotypes of IGF-I, IGF-II, MC4R, and CAPN1. BWs were collected from 0–16 weeks of age. The chickens were sacrificed at 16 weeks and individual carcass yields and meat qualities (drip loss, cooking loss, and shear force) were recorded. The correlations between BW and meat qualities were determined. Significant correlation between BW and cooking loss and shear force of breast meat and between BW and drip loss of thigh meat were detected (P<0.05); however, the magnitude of the association was low (−0.1–0.1). IGF-I was eliminated from the association analysis because genotype AA was lost and the frequency of occurrence of the AC genotype was low (0.04). Significant associations between IGF-II, CAPN1, and BW, and CAPN1 and meat quality were detected, while non-significant association between MC4R and BW was observed. The results indicated a low, negative relationship between BW and meat quality, and that the IGF-II and CAPN1 could be used as genetic markers in Leung Hang Khao chickens to improve growth and meat quality through breeding.

A comparison of the effects of post-mortem aging on breast meat from Cobb 500 and Hubbard ISA broilers

We compared the physical and chemical characteristics of the pectoralis major muscle from Cobb 500 and Hubbard ISA broilers and evaluated the effect of aging process for up to 7 days on meat quality. We used breast samples from male Cobb 500 (42 days of age; n = 60) and Hubbard ISA (85 days of age; n = 60) broilers. Twenty samples of each genotype were analysed 4 h post-slaughter (Control group). Another 20 samples of each genotype were aged in an incubator (2 ± 0.5°C) for 3 and for 7 days. Breast fillets were 23% heavier in the Cobb 500 group (306 g vs 248 g; P = 0.0009). Before aging, meat from Hubbard ISA broilers had higher (P < 0.001) water-holding capacity, which promotes the production of less exudate and possibly reduces nutritional losses during storage, which may be beneficial to the poultry industry. Despite being initially less tender, breast meat from Hubbard ISA broilers showed, during the aging process, a reduction (P < 0.05) of shear force (48.46–15.04 N), total collagen amount (6.0–4.8 g/kg) and myofibrillar fragmentation index (150.17–97.42) and had the same (P = 0.134) fat concentration (0.87 g/100 g) as that of breast meat from Cobb 500 broilers (0.93 g/100 g, respectively). Breast meat from Hubbard ISA broilers had a higher (P < 0.001) polyunsaturated fatty acid concentration, especially docosahexaenoic acid, which is beneficial to human health. Aging breast fillets for 3 days at 2°C is sufficient to tenderise the meat without reducing its juiciness, which suggests that the aging process can add value to free-range meat.

Poultry Meat Quality in Relation to Muscle Growth and Muscle Fiber Characteristics

Variations in the definition of poultry meat quality exist because the quality traits are not solely based on intrinsic and extrinsic factors but also consumers’ preference. Appearance quality traits (AQT), eating quality traits (EQT), and reliance quality traits (RQT) are the major factors focused by the consumer before buying good quality of poultry meat. AQT and EQT of poultry meat are controlled by physical and biochemical characteristics of muscle fibers which can be categorized into a total number of fibers (TNF), cross-sectional area of fibers (CSAF), and fiber type composition (FTC). In poultry meat, it has been shown that muscle fiber properties play a key role in meat quality because numerous studies have reported the relationships between quality traits and fiber characteristics. Despite intensive research has been carried out to manipulate the muscle fiber to improve poultry meat quality, demand in a rapid growth of poultry muscle has correlated to the deterioration in the meat quality. The present paper reviews the definition of poultry meat quality, meat quality traits, and variations of meat quality. Also, this review presents recent knowledge underlying the relationship between poultry meat quality traits and muscle fiber characteristics.

Programming Merino lambs by early feed restriction reduces growth rates and increases fat accretion during the fattening period with no effect on meat quality traits

The objective of the study was to determine the effect of early feed restriction on carcass and meat quality traits in Merino lambs. Twenty-four male Merino lambs (4.81±0.256kg) were assigned to two groups (12 animals in each group). The first group (ad libitum, ADL) was kept permanently with the dams. The second group (restricted, RES) was milk-restricted. After weaning (15kg), daily feed intake of all lambs was identical, but a lower gain: feed ratio was recorded in the RES group (0.320 vs. 0.261; P<0.001). After animals were slaughtered (27kg), lower ultimate pH and reduced yellow colouration of subcutaneous fat was recorded in meat from the RES lambs when compared to ADL group, whereas a trend towards a significant increment of intramuscular fat content and no effect on meat quality traits was observed in the RES lambs. Early feed restriction may be useful to increase intramuscular fat accretion in Merino lambs during the fattening period.

Invited review: Measurable biomarkers linked to meat quality from different pig production systems

Abstract. Biological processes underlie all livestock traits, including post-mortem meat quality traits. Biomarkers are molecular components of the biological processes showing differential expression associated with the phenotype of the trait. The phenotypes of the meat quality traits are determined by the animal's genotype interacting with the environment affecting the expression of the genome. The omics technologies enable measuring the expression of the genome at all levels: transcriptome, proteome, and metabolome. Associations between the phenotype of the traits and expressions measured with the omics techniques are a first step in developing biomarkers. Biomarkers enable the monitoring, diagnosis, and prediction of changes in meat quality related to external (environmental, e.g. feed and animal management conditions) stimuli and interactions with the genotype. In this paper we review the development of biomarkers for meat quality of pigs in diverse pig breeds, environments, and pork production chains.

Global transcriptome analysis identifies differentially expressed genes related to lipid metabolism in Wagyu and Holstein cattle

Fat deposition of beef cattle varies between breeds. However, the regulation mechanism is still not elucidated completely at molecular level. In the present study, we comparatively analyzed transcriptome of subcutaneous adipose tissue between Wagyu and Holstein cattle with a significant difference in fat deposition to identify key genes associated with fat metabolism and adipogenesis by high-throughput RNA-seq technology. A total of 59,149,852 and 69,947,982 high quality reads were generated, respectively. With further analysis, 662 differentially expressed genes were identified. Gene Ontology and KEGG pathway analysis revealed that many differentially expressed genes were enriched in several biological processes and pathways relevant to adipogenesis and lipid metabolism, in which PPAR and fatty acid metabolism signaling pathways with related genes such as PPARγ, PLIN2 and ELOVL6 et al. play a critical role. Protein-protein interaction network analysis showed EGR1, FOS, SERPINE1, AGT, MMP2 may have great impact on adipocyte differentiation and adipogenesis. Moreover, potential alternative splicing events and single nucleotide polymorphisms (SNPs) were also identified. In summary, we comprehensively analyzed and discussed the transcriptome of subcutaneous adipose tissue of Wagyu and Holstein cattle, which might provide a theoretical basis for better understanding molecular mechanism of fat metabolism and deposition in beef cattle.

Adiposity and adipogenic gene expression in four different muscles in beef cattle

Anatomical site and divergent functionalities of muscles can be related to differences in IMF content, metabolism and adipogenic gene expression. Then, potential differences in different muscles in beef cattle were studied. As a second objective, the main sources of experimental variability associated to RT-qPCR results were analyzed following a nested design in order to implement appropriate experimental designs minimizing gene expression variability. To perform the study Longissimus thoracis (LT), Semitendinosus (SM), Masseter (MS), Sternomandibularis (ST) and subcutaneous adipose tissue (SAT) samples of Pirenaica young bulls (n = 4) were collected for IMF, collagen and protein quantification, analysis of adipocyte size distribution and gene expression (PPARG, CEBPA, FAPB4 and WNT10B). A greater IMF content was observed in MS and SM muscles, which had a bimodal adipocyte size distribution while it was unimodal in the muscles LT and ST. This suggest that the different IMF accretion in the muscles studied might be related to different rates of hyperplasia and hypertrophy and that IMF might develop later in LT and ST muscles. The former differences were not mirrored by the expression of the genes analyzed, which might be related to the different contribution of mature and non-mature adipocytes to the total gene expression. When comparing IMF and SAT gene expression, late and early developing tissues respectively, expression of PPARG, CEBPA and FABP4 was higher in the SAT, in agreement with bigger cell size and numbers. The variability study indicates that the analytical factors that add higher variability to the gene expression are the sampling and RT and therefore, it would be appropriate to include those replicates in the design of future experiments. Based on the results, the use of MS and SM muscles could allow less expensive experimental designs and bigger sample size that could permit the detection of lower relevant differences in gene expression.

Principal component analysis of sensory properties of chicken breast muscle supplemented with different feed additives

The objective of the present study was to examine the effect of different dietary supplements (bee pollen, propolis, and probiotic) on sensory quality of chicken breast muscle. The experiment was performed with 180 one day-old Ross 308 broiler chicks of mixed sex. The dietary treatments were as follows: 1. basal diet with no supplementation as control (C); 2. basal diet plus 400 mg bee pollen extract per 1 kg of feed mixture (E1); 3. basal diet plus 400 mg propolis extract per 1 kg of feed mixture (E2); 4. basal diet plus 3.3 g probiotic preparation based on Lactobacillus fermentum added to drinking water (E3). Sensory properties of chicken breast muscle were assessed by a five-member panel that rated the meat for aroma, taste, juiciness, tenderness and overall acceptability. The ANOVA results for each attribute showed that at least one mean score for any group differs significantly (p ≤0.05). Subsequent Tukey's HSD revealed that only C group had significantly higher mean score (p ≤0.05) for each attribute compared with E2 group. As regards the E1 and E3 groups, there were not significant differences (p >0.05) in aroma, taste and tenderness when compared to C group, with the significantly lowest juiciness value (p ≤0.05) found in E3 group and significantly lower values of overall acceptability in both groups (p ≤0.05). In addition, it is noteworthy that control group received the highest raking scores for each sensory attribute, i.e. the supplements did not influence positively the sensory quality of chicken breast meat. Principal component analysis (PCA) of the sensory data showed that the first 3 principal components (PCs) explained 69.82% of the total variation in 5 variables. Visualisation of extracted PCs has shown that groups were very well represented, with E2 group clearly distinguished from the others.

Analysis of Differentially Expressed Genes in Gastrocnemius Muscle between DGAT1 Transgenic Mice and Wild-Type Mice

Adipose tissue was the major energy deposition site of the mammals and provided the energy for the body and released the external pressure to the internal organs. In animal production, fat deposition in muscle can affect the meat quality, especially the intramuscular fat (IMF) content. Diacylglycerol acyltransferase-1 (DGAT1) was the key enzyme to control the synthesis of the triacylglycerol in adipose tissue. In order to better understand the regulation mechanism of the DGAT1 in the intramuscular fat deposition, the global gene expression profiling was performed in gastrocnemius muscle between DGAT1 transgenic mice and wild-type mice by microarray. 281 differentially expressed transcripts were identified with at least 1.5-fold change and the p value < 0.05. 169 transcripts were upregulated and 112 transcripts were downregulated. Ten genes (SREBF1, DUSP1, PLAGL1, FKBP5, ZBTB16, PPP1R3C, CDC14A, GLUL, PDK4, and UCP3) were selected to validate the reliability of the chip's results by the real-time PCR. The finding of RT-PCR was consistent with the gene chip. Seventeen signal pathways were analyzed using KEGG pathway database and the pathways concentrated mainly on the G-protein coupled receptor protein signaling pathway, signal transduction, oxidation-reduction reaction, olfactory receptor activity, protein binding, and zinc ion binding. This study implied a function role of DGAT1 in the synthesis of TAG, insulin resistance, and IMF deposition.

Effect of divergent selection for intramuscular fat on sensory traits and instrumental texture in rabbit meat

Intramuscular fat (IMF) is one of the main parameters affecting meat quality. This work analyzes the effect of selection for IMF on sensory attributes and instrumental texture parameters in rabbit meat. A total of 115 rabbits after 6 generations of divergent selection for IMF were slaughtered at 9 or 13 wk (57 and 58 animals, respectively). For each animal, the left longissimus dorsi muscle (LD) was analyzed by near-infrared spectroscopy to measure IMF whereas the right LD was used for the sensory or instrumental texture analysis. Sensory attributes measured were rabbit odor, liver odor, rabbit flavor, liver flavor, aniseed flavor, hardness, juiciness, and fibrousness. The instrumental texture parameters maximum shear force, shear firmness, and total work to cut the sample were measured by a Warner-Bratzler shear test. The line selected for high IMF showed 58% greater IMF than the line selected for low IMF. This divergence affected firmness that was 9.9% greater in the low-IMF line, although no effect was found for the other instrumental texture traits. No effect of selection was observed in any odor or flavor, except for aniseed flavor, which was greater in the high-IMF line than in the low-IMF line. Age had an effect on IMF, instrumental texture parameters, and sensory attributes. Rabbits at 13 wk showed greater IMF and instrumental and sensory hardness and more intense odor and flavor and lower juiciness than rabbits at 9 wk.