Breed-Related Number and Size of Muscle Fibres and Their Response to Carcass Quality in Chickens

In ovo feeding of l-arginine and selenium nanoparticles influences post-hatch growth, muscle development, antioxidant status, and meat quality in slow-growing chickens

This study investigated the effects of in ovo feeding (IOF) of l-arginine (L-Arg), selenium nanoparticles (SeNP), and a combination of L-Arg and SeNP on the hatchability, post-hatch growth, muscle development, antioxidant status, and meat quality of slow-growing chickens. On day 18 of incubation, a total of 960 fertilized eggs with similar weights were randomly assigned to 4 treatment groups with 4 replicates of 60 eggs each: (1) non-injected control group (Control), (2) injected with 1% of L-Arg (IOF_L-Arg), (3) injected with 0.3 µg/egg of SeNP (IOF_SeNP), and (4), injected with 1% of L-Arg and 0.3 µg/egg of SeNP (IOF_L-Arg + SeNP). A completely randomized design was used. After hatching, 640 mixed-sex chicks were allocated to 4 treatment groups and split into 4 replicate pens (40 birds per pen). All groups of chicks were fed with commercial feed ad libitum until they reached 63 d of age and were subsequently weighed and slaughtered. The results of the present study showed that hatchability was similar among treatments. Final BW or breast muscle yield was not affected (P > 0.05) by IOF treatment. Chickens treated with IOF_L-Arg + SeNP exhibited decreased feed conversion ratio, drip loss, and increased protein content in breast meat (P < 0.05). The IOF_L-Arg + SeNP group exhibited a higher density of breast muscle fibers than the control group (P < 0.05). Overall, in ovo feeding of L-Arg combined with SeNP resulted in improved feed efficiency and enhanced antioxidant capacity at hatch without any adverse effects on chicken hatchability, health, or subsequent growth. Furthermore, meat from chickens in the IOF_L-Arg + SeNP group exhibited a preferable texture with a higher protein content.

Transcriptome sequencing to explore the effect of miR-214 on chicken primary myoblasts

MicroRNAs are involved in a series of biological processes, such as proliferation, differentiation and apoptosis of primary myoblasts. The research group found that miR-214 is highly expressed in chicken primary myoblasts (CPMs), so we used miR-214 as a starting point to explore the biological function of miR-214 in skeletal muscle growth and development. In this experiment, CPMs were cultured in vitro; miR-214 was overexpressed in CPMs; and cell samples were collected for subsequent transcriptome sequencing (RNA-seq). After miR-214 overexpression, we identified 97 differentially expressed genes (DEGs), of which 21 DEGs were up-regulated and 76 DEGs were down-regulated. After bioinformatics analysis, these DEGs were found to be significantly enriched in myofibrils, muscle system processes, myofibril assembly and other biological processes related to muscle development. The significantly enriched KEGGs include focal adhesion and type II diabetes mellitus. The protein network of DEGs was drawn by STRING and Cytoscape software, and 5 DEGs were randomly selected to verify the sequencing results by real-time fluorescence quantification. CAV3 is not only an important node protein in the protein network but also a member of the focal adhesion signaling pathway. It is speculated that miR-214 may regulate muscle development through the focal adhesion signaling pathway.

The hypoxia-inducible factor 1 pathway plays a critical role in the development of breast muscle myopathies in broiler chickens: a comprehensive review

In light of the increased worldwide demand for poultry meat, genetic selection efforts have intensified to produce broiler strains that grow at a higher rate, have greater breast meat yield (BMY), and convert feed to meat more efficiently. The increased selection pressure for these traits, BMY in particular, has produced multiple breast meat quality defects collectively known as breast muscle myopathies (BMM). Hypoxia has been proposed as one of the major mechanisms triggering the onset and occurrence of these myopathies. In this review, the relevant literature on the causes and consequences of hypoxia in broiler breast muscles is reviewed and discussed, with a special focus on the hypoxia-inducible factor 1 (HIF-1) pathway. Muscle fiber hypertrophy induced by selective breeding for greater BMY reduces the space available in the perimysium and endomysium for blood vessels and capillaries. The hypoxic state that results from the lack of circulation in muscle tissue activates the HIF-1 pathway. This pathway alters energy metabolism by promoting anaerobic glycolysis, suppressing the tricarboxylic acid cycle and damaging mitochondrial function. These changes lead to oxidative stress that further exacerbate the progression of BMM. In addition, activating the HIF-1 pathway promotes fatty acid synthesis, lipogenesis, and lipid accumulation in myopathic muscle tissue, and interacts with profibrotic growth factors leading to increased deposition of matrix proteins in muscle tissue. By promoting lipidosis and fibrosis, the HIF-1 pathway contributes to the development of the distinctive phenotypes of BMM, including white striations in white striping-affected muscles and the increased hardness of wooden breast-affected muscles.

Effect of in ovo creatine monohydrate on hatchability, post-hatch performance, breast muscle yield and fiber size in chicks from young breeder flocks

Younger broiler breeder flocks produce smaller eggs containing smaller yolks, with potentially lower energy reserves for the developing chick. Creatine is a naturally occurring energy source and is abundant in metabolically active tissues; providing this to chicks in ovo should provide additional energy to improve hatchability and post-hatch growth. Thus, post-hatch performance of male and female chicks hatched from younger breeder flocks supplemented with creatine monohydrate (CrM) in ovo was investigated. Four hundred eggs from Ross 308 breeder hens aged 27 to 29 wk were collected and at d 14 assigned to a treatment group and received 1) no injection, 2) 0.75% saline injection, or 3) 8.16 mg creatine monohydrate in 0.75% saline. At hatch 72 birds (24/treatment) were euthanized and BW, breast muscle, heart and liver weight were obtained, and breast muscle tissue was placed in 10% buffered formalin. Birds were then placed in raised metal pens (24 pens; 10-11 birds/pen; 8 replicates/treatment) and grown to d 42 with BW and pen feed intake measured once a week. At d 42, ninty-six birds were euthanized (2 male and 2 female/pen) and the process occurred as at hatch. Body composition was obtained for 48 birds (2/pen; 1 male,1 female) with a dual energy X-ray absorptiometry (DXA) scanner. Breast muscle tissue was processed for histological analysis and breast muscle fiber parameters were analyzed by ImageJ. While not statistically significant, the CrM treatment group saw an improved hatch rate (CrM: 93.5%, Saline: 88.6%, Control: 88.8%) and reduced early post hatch mortality. Chicks given in ovo CrM had significantly increased creatine concentrations in both liver and heart tissue at hatch compared to those in the saline and control groups. BW, BW gain, and final body composition parameters were not statistically different between treatments and in ovo CrM did not affect breast muscle fiber number or area. The creatine injection likely improved the energy status of the growing embryo resulting in the improved hatch rate but leaving little reserves for post-hatch growth.

Decoding the Effect of Age on the Taste Perception of Chicken Breast Soup Based on LC-QTOF-MS/MS Combined with a Chemometric Approach

A nontargeted fingerprinting approach combined with the chemometrics method and sensory analysis was used to assess the differences in taste-chemical compositions of chicken breast soup with different ages and their sensory qualities. The sensory evaluation results showed that the overall taste as well as the sourness, saltiness, and umami scores of the soup were increased with the age of chicken. Fifty-nine compounds were identified from four soup samples by liquid chromatography-tandem quadrupole time-of-flight mass spectrometry (LC-QTOF-MS/MS), and their total content was the highest in the 90 wk soup samples. Six upregulated compounds (carnosine, hypoxanthine, inosine, inosine 5'-monophosphate (5'-IMP), adenosine 5'-monophosphate (5'-AMP), and lactic acid) were identified as potential contributors to the taste characteristics of the 90 wk soup samples by orthogonal projections to latent structures-discriminant analysis (OPLS-DA). Additional experiments showed that 5'-AMP particularly contributed to the sourness of the soup, while carnosine contributed to the saltiness and umami of the soup.

A 2-bp deletion in intron 1 of TMEM182 is associated with TMEM182 mRNA expression and chicken body weight

1. Searching for molecular markers related to growth and carcase traits plays a critical role in improvement of the production performance of broilers. Previous studies found that transmembrane protein 182 (TMEM182) inhibits skeletal muscle development, growth, and regeneration, implying that the TMEM182 gene plays an important role during the development process of skeletal muscle.2. A novel 2-bp indel in intron 1 of TMEM182 was detected in a yellow chicken population derived from the cross of White Recessive Rock chickens with Xinghua chickens, and three genotypes II (inserted homozygote), ID (inserted and deleted heterozygote) and DD (deleted homozygote) were observed. Association analyses indicated that the indel was significantly associated with the body weight, muscle fibre area, breast muscle weight and wing weight in the F2 population.3. The expression of TMEM182 in leg muscle of chickens with II genotype was higher than that with DD genotype, with the 2-bp indel located in one of the putative PAX4 binding sites. Further research through luciferase assays revealed that the PAX4 could bind to the putative binding site and increase the TMEM182 transcription, with the 2-bp deletion disrupting the binding of PAX4.4. The present study provides evidence for the association of the novel 2-bp indel in intron 1 of TMEM182 with the growth and carcase traits of chickens. This 2-bp indel could be used as a genetic marker in broiler breeding.

Data Mining as a Tool to Infer Chicken Carcass and Meat Cut Quality from Autochthonous Genotypes

The present research aims to develop a carcass quality characterization methodology for minority chicken populations. The clustering patterns described across local chicken genotypes by the meat cuts from the carcass were evaluated via a comprehensive meta-analysis of ninety-one research documents published over the last 20 years. These documents characterized the meat quality of native chicken breeds. After the evaluation of their contents, thirty-nine variables were identified. Variables were sorted into eight clusters as follows; weight-related traits, water-holding capacity, colour-related traits, histological properties, texture-related traits, pH, content of flavour-related nucleotides, and gross nutrients. Multicollinearity analyses (VIF ≤ 5) were run to discard redundancies. Chicken sex, firmness, chewiness, L* meat 72 h post-mortem, a* meat 72 h post-mortem, b* meat 72 h post-mortem, and pH 72 h post-mortem were deemed redundant and discarded from the study. Data-mining chi-squared automatic interaction detection (CHAID)-based algorithms were used to develop a decision-tree-validated tool. Certain variables such as carcass/cut weight, pH, carcass yield, slaughter age, protein, cold weight, and L* meat reported a high explanatory potential. These outcomes act as a reference guide to be followed when designing studies of carcass quality-related traits in local native breeds and market commercialization strategies.

Variability of Meat and Carcass Quality from Worldwide Native Chicken Breeds

The present research aimed to determine the differential clustering patterns of carcass and meat quality traits in local chicken breeds from around the world and to develop a method to productively characterize minority bird populations. For this, a comprehensive meta-analysis of 91 research documents that dealt with the study of chicken local breeds through the last 20 years was performed. Thirty-nine traits were sorted into the following clusters: weight-related traits, histological properties, pH, color traits, water-holding capacity, texture-related traits, flavor content-related nucleotides, and gross nutrients. Multicollinearity problems reported for pH 72 h post mortem, L* meat 72 h post mortem, a* meat 72 h post mortem, sex, firmness, and chewiness, were thus discarded from further analyses (VIF < 5). Data-mining cross-validation and chi-squared automatic interaction detection (CHAID) decision tree development allowed us to detect similarities across genotypes. Easily collectable trait, such as shear force, muscle fiber diameter, carcass/pieces weight, and pH, presented high explanatory potential of breed variability. Hence, the aforementioned variables must be considered in the experimental methodology of characterization of carcass and meat from native genotypes. This research enables the characterization of local chicken populations to satisfy the needs of specific commercial niches for poultry meat consumers.

A comparative study of meat quality and vibrational spectroscopic properties of different chicken breeds

Chicken breed is one of the key factors that influence meat quality. The quality attributes of breast meat from commercial broiler (CB), Thai native chicken (NC, Leung Hang Khao), and the crossbred Korat chicken (KC) were investigated via synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy, Fourier transform Raman (FT-Raman) spectroscopy, and physicochemical analysis. The protein and carbonyl contents of KC and NC meats were higher than that of CB meat, but the lipid content was lower (P < 0.05). CB meat was characterized by high moisture, lightness (L*), and presence of taste-active nucleotides, namely, inosine 5′-monophosphate (IMP) and guanosine 5′-monophosphate (GMP). Moreover, NC meat had the highest insoluble collagen and inosine contents (P < 0.05). The predominant protein secondary structures of KC and NC meats were β-turns and random coils, whereas α-helices were mainly found in CB meat. Based on principal component analysis, the meat quality and spectra were clearly separated by breeds. The high moisture and lipid content of meat corresponded to O–H stretching (3,203 cm⁻¹) and C–H stretching (2,854 cm⁻¹) in the FT-Raman spectra, whereas PO₂⁻ stretching (1,240 cm⁻¹), measured via SR-FTIR, was well correlated with the IMP content. In addition, the FT-Raman wavenumber of 934 cm⁻¹, indicating C–C stretching, was correlated with high water-holding capacity (WHC) in KC meat. The quality of meat from slow- and fast-growing chickens significantly varies. Vibrational spectroscopy is a powerful technique that provides insightful molecular information correlated with various meat attributes.

Transcriptome Analysis Reveals the Differentially Expressed Genes Associated with Growth in Guangxi Partridge Chickens

The Guangxi Partridge chicken is a well-known chicken breed in southern China with good meat quality, which has been bred as a meat breed to satisfy the increased demand of consumers. Compared with line D whose body weight is maintained at the average of the unselected group, the growth rate and weight of the selected chicken group (line S) increased significantly after breeding for four generations. Herein, transcriptome analysis was performed to identify pivotal genes and signal pathways of selective breeding that contributed to potential mechanisms of growth and development under artificial selection pressure. The average body weight of line S chickens was 1.724 kg at 90 d of age, which showed a significant increase at 90 d of age than line D chickens (1.509 kg), although only the internal organ ratios of lung and kidney changed after standardizing by body weight. The myofiber area and myofiber density of thigh muscles were affected by selection to a greater extent than that of breast muscle. We identified 51, 210, 31, 388, and 100 differentially expressed genes (DEGs) in the hypothalamus, pituitary, breast muscle, thigh muscle, and liver between the two lines, respectively. Several key genes were identified in the hypothalamus-pituitary-muscle axis, such as FST, THSB, PTPRJ, CD36, PITX1, PITX2, AMPD1, PRKAB1, PRKAB2, and related genes for muscle development, which were attached to the cytokine–cytokine receptor interaction signaling pathway, the PPAR signaling pathway, and lipid metabolism. However, signaling molecular pathways and the cell community showed that elevated activity in the liver of line S fowl was mainly involved in focal adhesion, ECM-receptor interaction, cell adhesion molecules, and signal transduction. Collectively, muscle development, lipid metabolism, and several signaling pathways played crucial roles in the improving growth performance of Guangxi Partridge chickens under artificial selection for growth rate. These results support further study of the adaptation of birds under selective pressure.

Influence of Post Mortem Muscle Activity on Turkey Meat Quality

Wing flapping and body movement can occur during the slaughter of poultry. Wing movement and flapping are driven primarily by the breast muscles (Pectoralis major and minor), and this muscle activity may have implications for meat quality. The objective of this study was to evaluate turkey post mortem activity during slaughter at a commercial poultry processing plant. Post mortem activity (during bleeding) was scored on 5,441 male turkeys, from six different genetic lines, using a 1–4 scale from none to severe wing flapping. Meat quality was measured on these birds in terms of pH (initial, ultimate, delta or change), color (L^*, a^*, b^*), and physiochemical traits (drip loss, cooking loss, shear force). Linear mixed models were used to analyze the effect of activity (score 1–4), genetic line (A–F), and season (summer vs. autumn) on the nine meat quality traits. Post mortem activity influenced a^*, drip loss, and shear force although the magnitude of the effects was small. There was an effect (P < 0.05) of genetic line on all the meat quality traits except for L^*, cooking loss, and shear force. In general, larger, faster-growing lines had higher pH, but the relationship between the lines for the other traits is not as clear. Season affected all the meat quality traits, except for pH_delta, with meat having a higher pH, L^*, b^*, drip loss, cooking loss, and shear force in the summer. This study provides an exploratory assessment of post mortem activity in turkeys and identifies meat quality traits which are most affected while also accounting for the effects of genetic line and season. Although identified effect sizes are small, the cumulative effect on turkey meat quality may be more substantial.

SAP30 Gene Is a Probable Regulator of Muscle Hypertrophy in Chickens

Animals with muscle hypertrophy phenotype are targeted by the broiler industry to increase the meat production and the quality of the final product. Studies characterizing the molecular machinery involved with these processes, such as quantitative trait loci studies, have been carried out identifying several candidate genes related to this trait; however, validation studies of these candidate genes in cell culture is scarce. The aim of this study was to evaluate SAP30 as a candidate gene for muscle development and to validate its function in cell culture in vitro. The SAP30 gene was downregulated in C2C12 muscle cell culture using siRNA technology to evaluate its impact on morphometric traits and gene expression by RNA-seq analysis. Modulation of SAP30 expression increased C2C12 myotube area, indicating a role in muscle hypertrophy. RNA-seq analysis identified several upregulated genes annotated in muscle development in treated cells (SAP30-knockdown), corroborating the role of SAP30 gene in muscle development regulation. Here, we provide experimental evidence of the involvement of SAP30 gene as a regulator of muscle cell hypertrophy.

Evaluation of Meat from Native Chickens: Analysis of Biochemical Components, Fatty Acids, Antioxidant Dipeptides, and Microstructure at Two Slaughter Ages

This study examined biochemical components, fatty acids, antioxidant dipeptides, and muscle fiber density of breast and thigh muscles from Korean new native chicken strains (A and B) at two slaughter ages, compared with white semi-broiler (W) or broilers. The pH values were different by chicken breed. The new native strains had the lowest fat content in the breast at 12 wk (p<0.05). Regardless of the muscles, A and B at 12 wk had higher levels of arachidonic acid (ARA; C20:4), docosahexaenoic acid (DHA; C22:6), and nervonic acid (C24:1) than broilers (p<0.05). A similar result was observed for the polyunsaturated fatty acids (PUFAs) and polyunsaturated and saturated fatty acids ratio (P/S) content in the breast. Irrespective of the muscles, A and B enriched with omega-3 fatty acids had a lower ω-6/ω-3 PUFA ratio than broilers (p<0.05) at 12 wk. Of the antioxidant di-peptides, the anserine contents were highest in A and B than in the W or broilers (p<0.05), regardless of the muscles and slaughter ages. Furthermore, the breast meat from A and B contained a higher muscle fiber density for both slaughter ages than the W and broilers (p<0.05). Based on these findings, even if the commercial birds (broilers or W) are raised under the similar environmental conditions as A and B, the new native chicken strains have distinct meat quality attributes, particularly higher ARA and DHA levels, lower ω-6/ω-3 PUFA ratio, and higher anserine contents.

Correlations between first order echotextural characteristics and chemical composition of pectoralis major muscles in broiler chickens receiving different dietary fat supplements

This study examined the quantitative relationships among ultrasonographic image attributes and chemical composition of the pectoralis major muscles in broiler chickens that received four different dietary fat supplements (Group SO: soybean oil; Group FO: flaxseed oil; Group SO+FO: soybean oil+flaxseed oil; and Group BT: beef tallow; n=10 birds/group). Ultrasonograms of birds’ pectoral muscles, in a transverse (T) and longitudinal (L) plane, were obtained just before slaughter at 6 weeks of age and were subjected to digital image analyses to determine mean pixel intensity (MPI) and pixel heterogeneity values (standard deviation of numerical pixel values; MPH; a.k.a first order echotextural characteristics). Thirty-eight chemical characteristics of the muscles were determined post-mortem (crude fat, protein, and dry matter as well as fatty acid profiles) and were analyzed for correlations with the echotextural variables. A total of 12 (L-MPI: 7; L-MPH: 4; and T-MPH: 1 correlation), 5 (L-MPI: 2; L-MPH: 2; and T-MPI: 1 correlation), 15 (L-MPI: 10; T-MPI: 4; and T-MPH: 1 correlation) and 8 (L-MPI: 2; L-MPH: 1; and TMPH: 5 correlations) significant correlations were recorded in Groups SO, FO, SO+FO and BT, respectively. When the data were pooled for all 40 birds studied, significant correlations with echotextural attributes were recorded for eighteen different chemical constituents, with the strongest overall correlation found between crude fat content and T-MPI (r=0.52, P=0.0005). In conclusion, there exists a potential application for ultrasonographic imaging in situ combined with computerized image analysis to estimate certain chemical constituents of pectoralis major muscles in broiler chickens. However, the existence and strength of correlations among ultrasonographic image attributes and muscle composition are affected by the source of dietary fat and relative abundance (“threshold concentrations”) of individual chemical components.

Promising Role of Growth Hormone-Boosting Peptide in Regulating the Expression of Muscle-Specific Genes and Related MicroRNAs in Broiler Chickens

Appropriate skeletal muscle development in poultry is positively related to increasing its meat production. Synthetic peptides with growth hormone-boosting properties can intensify the effects of endogenous growth hormones. However, their effects on the mRNA and miRNA expression profiles that control muscle development post-hatching in broiler chicks is unclear. Thus, we evaluated the possible effects of synthetic growth hormone-boosting peptide (GHBP) inclusion on a chicken's growth rate, skeletal muscle development-related genes and myomiRs, serum biochemical parameters, and myofiber characteristics. A total of 400 one-day-old broiler chicks were divided into four groups supplied with GHBP at the levels of 0, 100, 200 and 300 μg/kg for 7 days post-hatching. The results showed that the highest levels of serum IGF-1 and GH at d 20 and d 38 post-hatching were found in the 200 μg/kg GHBP group. Targeted gene expression analysis in skeletal muscle revealed that the GHBP effect was more prominent at d 20 post-hatching. The maximum muscle development in the 200 μg/kg GHBP group was fostered by the upregulation of IGF-1, mTOR, myoD, and myogenin and the downregulation of myostatin and the Pax-3 and -7 genes compared to the control group. In parallel, muscle-specific myomiR analysis described upregulation of miR-27b and miR-499 and down-regulation of miR-1a, miR-133a, miR-133b, and miR-206 in both the 200 and 300 μg/kg GHBP groups. This was reflected in the weight gain of birds, which was increased by 17.3 and 11.2% in the 200 and 300 μg/kg GHBP groups, respectively, when compared with the control group. Moreover, the maximum improvement in the feed conversion ratio was achieved in the 200 μg/kg GHBP group. The myogenic effects of GHBP were also confirmed via studying myofiber characteristics, wherein the largest myofiber sizes and areas were achieved in the 200 μg/kg GHBP group. Overall, our findings indicated that administration of 200 μg/kg GHBP for broiler chicks could accelerate their muscle development by positively regulating muscle-specific mRNA and myomiR expression and reinforcing myofiber growth.

Effect of housing system and feed restriction on meat quality of medium-growing chickens

The aim of the study was to evaluate the differences in meat quality of 420 Hubbard JA757 cockerels in relation to the housing system (litter and mobile box) and level of mixed feed (ad libitum [AL], reducing the level by 20% [R20] and 30% [R30]). Three groups of chickens were housed in litter boxes for the entire fattening period (stocking density: 0.094 m²/bird). The other 3 groups were housed in litter boxes until 28 d of age and then relocated into mobile boxes (stocking density: 0.154 m²/bird) on pasture until the end of the experiment at 57 d of age. Restricted groups received a reduced diet level from 29th to 57th d of age. Feed mixture restriction increased the pasture vegetation intake of chickens from 2.63 to 3.50 (R20) and 3.94 g of dry matter/bird/d (R30). Restriction adversely affected the dressing percentage (P < 0.001) and breast yield (P < 0.001), while the leg yield (P < 0.001) was increased with increasing restriction levels. Meat of chickens housed in mobile boxes on a pasture showed lower cooking loss (P < 0.001) and higher redness and yellowness values in the skin (P = 0.030 and P = 0.026; respectively) and meat (P = 0.008 and P < 0.001; respectively). The fragile meat after cooking was observed in chickens reared on litter (P = 0.001). As the level of restriction increased, the number of muscle fibres (P = 0.001) increased, and their cross-sectional area (P = 0.001) and diameter (P = 0.002) decreased. The highest contents of lutein (P = 0.002) and zeaxanthin (P = 0.006) in breast muscle were found in chickens housed in mobile boxes and fed 80% and 70% AL. However, the concentrations of α- and γ-tocopherol (P = 0.006 and P = 0.003) were negatively affected by feed restriction. A 30% reduction in feed level in outdoor housed chickens led to a decrease in oxidative stability (P = 0.024). Feed restriction (R20) in chickens housed in mobile boxes significantly increased the n3 fatty acids content (P = 0.002) and h/H index (P = 0.005) and reduced the n6/n3 ratio (P < 0.001) and atherogenic (P < 0.001) and thrombogenic index (P = 0.003), which possess a health benefits for human. In addition, restriction of mixed feed decreased cholesterol content in breast meat (P = 0.042). It might be concluded that, in terms of meat quality, cereal diet restriction of 20% in medium-growing cockerels housed in mobile boxes on a pasture is beneficial. The higher level of restriction does not lead to further improvement in meat quality indicators.

Effects of maternal dietary energy restriction on breast muscle fibre development in the offspring of broiler breeders

Objective

The effects of maternal dietary energy levels on breast muscle fibre development in offspring of broiler breeders were investigated.

Methods

A total of 480 20-week-old Arbor Acres (AA) healthy female broiler breeders, with an average body weight of 2.33±0.01 kg, were randomly divided into 4 treatment groups with 6 replicates and 20 broiler breeders for each replicate and fed a corn and soybean meal diet with 100%, 80%, 70%, and 50% energy levels, respectively. Approximately 300 eggs per treatment were collected for incubation for 6 days. Then, 120 0-day-old female broilers at each energy level were randomly selected and divided into 6 replicates with 20 broilers for each replicate, with this experimental phase with the offspring lasting for 49 days.

Results

Compared with the 100% energy group, the breast muscle fibre diameter at embryonic day 21 in the 80% energy group was significantly reduced (p<0.05). In the 80% energy group, the muscle fibre density of the breast increased significantly (p<0.05) at embryonic days 15 and 21. The breast muscle fibre diameter of the offspring in each group was significantly decreased (p<0.05) on the 1st day. The breast muscle sarcomere length of the embryos in the 80% energy group was significantly higher (p<0.05) than those in the 70% and 50% energy groups. Compared with the 100% energy group, the expression of the myostatin gene in the offspring was significantly decreased (p<0.05).

Conclusion

In conclusion, the effects of a maternal dietary energy level of 80% in this study were found to be optimal for breast muscle fibre development in offspring, which indicated that the metabolic energy level of AA broilers of 9.36 MJ/kg for the mid-term diet for laying eggs has a more practical significance.

MicroRNA-214 Inhibits Chicken Myoblasts Proliferation, Promotes Their Differentiation, and Targets the TRMT61A Gene

The proliferation and differentiation of myoblasts is an important process of skeletal muscle development. In this process, microRNAs (miRNAs) play an important role in the proliferation and differentiation of chicken primary myoblasts (CPMs). Our previous study found that miR-214 and the tRNA methyltransferase 61A (TRMT61A) gene were differentially expressed in different stages of proliferation and differentiation. Therefore, this study aimed to explore the effect of miR-214 on the proliferation and differentiation of CPMs and the functional relationship between miR-214 and TRMT61A. In this study, we detected the effect of miR-214 on the proliferation of CPMs by qPCR, flow cytometry, CCK-8, and EdU after the overexpression and interference of miR-214. qPCR, Western blotting, and indirect immunofluorescence were used to detect the effect of miR-214 on the differentiation of the CPMs. The expression patterns of miR-214 and TRMT61A were observed at different time points of differentiation induced by the CPMs. The results show that miR-214 inhibited the proliferation of the CPMs and promoted the differentiation of the CPMs. The Dual-Luciferase Reporter assay and the expression pattern of miR-214 and TRMT61A suggested that they had a negative regulatory target relationship. This study revealed the function and regulatory mechanism of miR-214 in the proliferation and differentiation of CPMs.

Machine assisted classification of chicken, beef and mutton tissues using optical polarimetry and Bagging model

Optical polarimetry has been used to characterize muscle tissue samples of chicken, beef and mutton, exhibiting statistically significant (p <  0.01) differences in total depolarization and retardance of three tissue groups. Herein, the total depolarization and retardance were utilized to differentiate and classify the three tissue groups. Specifically, the Bagging classification algorithm was employed for this multi-class differentiation. The performance of the optical polarimetry in tandem with the Bagging model for machine-assisted classification of the three tissue groups was assessed in terms of a comprehensive set of evaluation metrics. The Bagging model correctly classified 47/48, 19/20 and 15/18, whereas the sensitivity (Sn = 97.9 %, 82.6 %, 100 %), specificity (Sp = 97.4 %, 98.4 %, 95.8 %), positive predictive values (PPV = 0.97, 0.95, 0.83) and negative predictive values (NPV = 0.97, 0.94, 1.0) were calculated for the chicken, beef and mutton tissue samples, respectively. This automatic classification of the three tissue samples indicates a novel application of the optical polarimetry in the meat industry.

Quality, composition, and consumer evaluation of meat from slow-growing broilers relative to commercial broilers

During the last few years, slow-growing broiler market share is steadily increasing. Hence, new strains of slow-growing broilers are being introduced to meet the demand. Indbro broiler is such one strain developed to cater the demand for slow-growing broiler meat. Therefore, it is necessary to understand the meat quality of this new variety of slow-growing broiler meat. In this context, the present study was undertaken to compare the meat quality, composition, and consumer preference of slow-growing and commercial white broiler chicken meats. Commercial white broilers (vencobb strain) used in this study weighed approximately 2.0 kg and are 36 days old. The slow-growing birds were from Indbro strain which is multicolored and costing about 30 to 50% higher price in local markets. The dressing percentage, breast meat yield, meat bone ratio, and muscle fiber diameter were higher (P < 0.05) in commercial broilers. However, the cooking yield of drumstick and breast meat did not differ significantly between 2 genotypes. Shear force value and protein content of thigh meat were higher (P < 0.05) in slow-growing broiler as compared to the commercial broiler. Slow-growing boiler breast meat contains significantly (P < 0.05) lower total fatty acid and saturated fatty acid content. A significant (P < 0.05) percentage (67%) of consumers preferred the meat and meat products prepared from slow-growing broiler meat. During "paired comparison" test the semi-trained panelists could able to differentiate between slow-growing and fast-growing broiler meat. All the sensory attributes of meat and meat products from slow-growing broilers were similar to commercial broiler. Therefore, slow-growing broiler chicken has the potential to provide the tasty and alternate poultry meat to consumers.

Mechanism and Functions of Identified miRNAs in Poultry Skeletal Muscle Development – A Review

Development of the skeletal muscle goes through several complex processes regulated by numerous genetic factors. Although much efforts have been made to understand the mechanisms involved in increased muscle yield, little work is done about the miRNAs and candidate genes that are involved in the skeletal muscle development in poultry. Comprehensive research of candidate genes and single nucleotide related to poultry muscle growth is yet to be experimentally unraveled. However, over a few periods, studies in miRNA have disclosed that they actively participate in muscle formation, differentiation, and determination in poultry. Specifically, miR-1, miR-133, and miR-206 influence tissue development, and they are highly expressed in the skeletal muscles. Candidate genes such as CEBPB, MUSTN1, MSTN, IGF1, FOXO3, mTOR, and NFKB1, have also been identified to express in the poultry skeletal muscles development. However, further researches, analysis, and comprehensive studies should be made on the various miRNAs and gene regulatory factors that influence the skeletal muscle development in poultry. The objective of this review is to summarize recent knowledge in miRNAs and their mode of action as well as transcription and candidate genes identified to regulate poultry skeletal muscle development.

Dissection of Myogenic Differentiation Signatures in Chickens by RNA-Seq Analysis

A series of elaborately regulated and orchestrated changes in gene expression profiles leads to muscle growth and development. In this study, RNA sequencing was used to profile embryonic chicken myoblasts and fused myotube transcriptomes, long non-coding RNAs (lncRNAs), and messenger RNAs (mRNAs) at four stages of myoblast differentiation. Of a total of 2484 lncRNA transcripts, 2288 were long intergenic non-coding RNAs (lincRNAs) and 198 were antisense lncRNAs. Additionally, 1530 lncRNAs were neighboring 2041 protein-coding genes (<10 kb upstream and downstream) and functionally enriched in several pathways related to skeletal muscle development that have been extensively studied, indicating that these genes may be in cis-regulatory relationships. In addition, Pearson’s correlation coefficients demonstrated that 990 lncRNAs and 7436 mRNAs were possibly in trans-regulatory relationships. These co-expressed mRNAs were enriched in various developmentally-related biological processes, such as myocyte proliferation and differentiation, myoblast differentiation, and myoblast fusion. The number of transcripts (906 lncRNAs and 4422 mRNAs) differentially expressed across various stages declined with the progression of differentiation. Then, 4422 differentially expressed genes were assigned to four clusters according to K-means analysis. Genes in the K1 cluster likely play important roles in myoblast proliferation and those in the K4 cluster were likely associated with the initiation of myoblast differentiation, while genes in the K2 and K3 clusters were likely related to myoblast fusion. This study provides a catalog of chicken lncRNAs and mRNAs for further experimental investigations and facilitates a better understanding of skeletal muscle development.

Combined effect of divergent selection for breast muscle ultimate pH and dietary amino acids on chicken performance, physical activity and meat quality

Responses to changes in dietary Lys and other essential amino acid (AA) concentrations were evaluated in 480 male and female broilers originating from two lines divergently selected for high (pHu+) or low (pHu-) ultimate pH (pHu) of breast muscle. The two genetic lines were fed with two grower isoenergetic diets differing in both true digestible Lys (control=10.2 g/kg and experimental=7.0 g/kg) and amounts of other essential AA calculated in relation to Lys, which were sufficient for the control diet or in excess for the experimental diet. There were six repetitions per treatment. Birds were weighed individually at days 0, 21, 28 and 43. Feed consumption was recorded per pen and feed conversion was calculated over the growing period. The physical activity and walking ability of broilers were recorded during the whole rearing period. Breast and leg yield, and abdominal fat percentage were measured at 43 days of age, as were pHu, color, drip and cooking loss, Warner-Bratzler shear force, and curing-cooking yield of the breast Pectoralis major and pHu of the thigh Sartorius muscle. Divergent selection greatly affected most breast meat quality traits without significantly changing growth rate or feed efficiency. When subjected to a variation in dietary intake of AA, birds from the two genotypes responded in a similar way in terms of animal's growth, feed efficiency, body composition and meat quality traits. Although line and diet did not affect physical or feeding activities of the broilers, a significant effect of line-by-diet interaction was observed on gait score. Contrary to the pHu- birds, the walking ability of pHu+ birds was impaired when fed the control diet that favored growth and breast muscle development and limited storage of carbohydrate in muscle.