Comparison of muscle fiber characteristics and glycolytic potential between slow- and fast-growing broilers

Effects of the early incubation temperature on the muscle physiology, meat quality, bone strength and gait score in Ross broilers

1. Modern broiler chickens are among the most efficient livestock in terms of resource requirements and production time. To maintain and improve production efficiency and meat quality and account for welfare problems, early interventions, such as incubation temperature, require investigation2. In this study, Ross 308 broiler eggs were incubated at either 36.5°C or 38.5°C on embryonic days (ED) 4-7. The control group eggs were incubated at a constant temperature of 37.5°C. Musculus pectoralis and musculus gastrocnemius samples were taken for the investigation of muscle physiology, and the tibia was sampled for bone strength analysis from chickens aged 35 and 36 d. In addition, meat quality was analysed and gait scoring was performed.3. The performance of chickens in the 36.5°C group was inferior to those in the other groups up to d 10 post-hatch, but compensatory growth was seen by d 35 of age. Meat quality was unaffected, but significant differences between sexes were observed. Males had lighter meat colour than females. Muscle glycogen and intramuscular fat were unaffected by the incubation temperature, but the muscularis pectoralis and gastrocnemius intramuscular fat contents were greater in males than in females, accompanied by the increased expression of enzymes involved in lipolysis. In the 38.5°C group, males had less bone elasticity than females, and the inverse was observed in the other groups. Gait scores were affected by sex but not incubation temperature.4. The results of this study showed a stronger effect of sex than incubation temperature on broiler muscle physiology, bone strength, performance and meat quality.

Age-related morphometry, typology and spatial distribution of anterior latissimus dorsi muscle fibre in broiler chicken

The acquisition and processing of muscle tissue images through optical microscopy, along with manual and semi-automatic software techniques, present significant constraints on comprehensive research of a muscle's entire cross-sectional area. To address this limitation, we focused on the anterior latissimus dorsi (ALD) muscle, enabling us to analyse its complete cross-section on a single slide throughout all study stages. This allowed for a detailed assessment, incorporating age-related variations, of histoenzymatic activity across the entire cross-sectional area, along with fibre typology and spatial distribution, and to encourage comparative research across vertebrates to examine species-specific, genetic, ecological and functional influences on histo-enzymomorphometric changes. Leveraging advancements in image acquisition and processing technologies, including slide scanning and automated software, we conducted a comprehensive study on broiler chickens (Gallus gallus Domesticus) at post-hatch ages (D0, D7, D14, D21, D28, D35, D42, D49 and D56), with 10 subjects per age group. The myofibrillar network was visualized using Azorubin staining, while identification of different fibre types in the ALD muscle was achieved through co-revelation of ATPase activity at acidic pH (4.10). Our investigation revealed a progressive decline in the total number of muscle fibres with age. The ALD muscle demonstrated variability in intramuscular distribution, with type IIIa fibres dispersed across the entire muscle surface, showing a consistent increase in percentage with age. Conversely, type IIIb fibres were initially well distributed across the muscle surface during early growth stages but exhibited a gradual decrease with age, particularly in the caudal half of the muscle, reaching minimal values in adulthood. Type IIa fibres were scarce in early ages but appeared in later stages, with percentages not exceeding 5%. The coefficient of variability of type IIa fibres was notably high, indicating the presence of multiple fibre types sharing a common negative reaction to ATPase revelation at acidic pH. This phenomenon suggests a potential conversion of type IIIb fibres into type IIa and IIb fibres. In conclusion, our histoenzymatic study of the entire cross-sectional area of the ALD muscle has provided novel insights into fibre typology and spatial distribution within muscle bundles. Further research to unravel the mechanisms of fibre-type distribution leading to explore the genetic effects of domestication and ecological pressures across species.

Main lipid sources affecting key aroma volatile compounds in Chinese native chicken

There are hundreds of local chicken breeds in China, which have a large consumer market due to their excellent flavor. In this study, Beijing You chicken and Wenchang chicken, were used to analyze the relationship between lipid and meat aroma through volatolomics and full-spectrum metabonomics. Multivariate statistical analysis identified 15 key meat aroma volatile organic compounds (VOCs) and their closely related metabolites, mainly including triglycerides (TGs), glycerophospholipids (GPs) and small peptides. Correlation network analysis of lipid metabolites revealed that GPs and TGs were highly positively correlated with unsaturated fatty acids, such as C20:5 and C16:1, which were involved in the formation of aldehydes. In chicken, phospholipid markers, mainly lysophosphatidylethanolamines and lysophosphatidylcholines, contributed significantly to the formation of meat flavor VOCs. Overall, this study revealed the relationship between different lipids and characteristic VOCs in chicken, providing a new understanding of the formation of VOCs and a theoretical basis for flavor regulation.

Distinct roles of the circMKNK2/miR-15a Axis in regulating chicken skeletal muscle development and glucose metabolism

Circular RNAs (circRNAs) have emerged as critical regulators of biological processes, but their roles in avian muscle development remain less explored. Here we characterize circMKNK2, a novel circRNA derived from the MKNK2 gene, which is highly expressed in slow-growing Silky chickens compared to fast-growing broilers. Functional studies demonstrate that circMKNK2 acts as a sponge for miR-15a, with overexpression inhibiting myoblast proliferation, differentiation, apoptosis, and glucose metabolism, while miR-15a knockdown produces similar effects except for enhanced glucose uptake. RNA-seq analysis identified 2189 differentially expressed genes regulated by circMKNK2 in chicken primary myoblasts, including key targets of the circMKNK2/miR-15a axis such as PIK3R1 (a core node regulating PI3K-Akt signaling), BHLHE41, KANK1, and ARHGAP20. Pathway analysis revealed modulation of myogenesis through Calcium signaling pathway, ECM-receptor interaction, Neuroactive ligand-receptor interaction and immune-related pathways (Toll-like receptor, cytokine-cytokine receptor interactions). Further analysis highlighted the circMKNK2/miR-15a axis's role in suppressing myogenesis through transcriptional regulation of key factors (e.g., SOX7, MAF) and metabolic reprogramming. Unlike pro-myogenic circRNAs, circMKNK2 uniquely inhibited muscle development and glucose metabolism, suggesting its involvement in breed-specific phenotypic differences. This study provides insights into circRNA-mediated regulation of muscle biology and offers potential targets for improving poultry production through genetic and metabolic modulation.

The m6A modification regulates the composition of myofiber types in chicken skeletal muscle

As a widespread epigenetic RNA modification, N6-methyladenosine (m6A) plays essential regulatory roles in multiple biological processes. However, its function in maintaining and modulating myofiber-type properties remains largely unknown. To investigate the post-transcriptional modification underlying the myofiber type diversity in chicken skeletal muscle, we evaluated the m6A methylation levels of chicken skeletal muscles with different phenotypic traits, and profiled a transcriptome-wide m6A map in the oxidative and glycolytic skeletal muscles by methylated RNA immunoprecipitation sequencing (MeRIP-seq). Our results showed that the levels of m6A methylation in chicken skeletal muscles were closely related to the composition of myofiber types. The m6A methylation level of anterior latissimus dorsi (ALD, typical oxidative skeletal muscle) was the highest among the three muscles and significantly higher than that of the pectoralis major (PM, typical glycolytic skeletal muscle) (P<0.05). We found that about 24.77 % and 33.50 % of genes were modified by m6A methylation in the PM and ALD, respectively, and identified 6,530 and 9,965 m6A peaks, which were mainly located in the coding sequence (CDS) and stop codon. About 3.14 % of m6A modified genes showed significantly differential methylation levels between these two muscles. Intriguingly, the myofiber type-related genes, such as MYOT, TPM3, TPM1, PDK1, MBNL1, and MYH1G, showed differences in m6A methylation and mRNA expression. Further analysis revealed that the m6A methylation was positively correlated with gene expression homeostasis. It is exciting we found that the expression level of ALKBH5 mRNA and protein, was closely related to the composition of myofiber types. ALKBH5 over-expression could regulate the expression levels of genes related to muscle contraction and metabolism, including MYH1E, MYH1G, MYH7B, PDK1, and TPM1, suggesting the effect of ALKBH5 on the formation of myofiber-type properties in chicken skeletal muscle. Our results contribute to a better understanding of epigenetic factors involved in forming chicken myofiber-type properties and provide new targets for further investigation into chicken's growth development and meat quality.

Muscle fiber types switched during the development of experimental autoimmune myasthenia gravis via the PI3K/Akt signaling pathway

As one of the largest organs of our human body, skeletal muscle has good research prospects in myasthenia gravis (MG), the symptoms of which include systemic skeletal muscle weakness. Skeletal muscle is composed of two types of muscle fibers. Different fiber subtypes can be converted into each other; however, the underlying mechanism is not yet clear. In this paper, we firstly established an experimental autoimmune myasthenia gravis (EAMG) rat model and found that the skeletal muscle fibers of the EAMG group were atrophied, with a change in the proportion of fiber subtypes, which switched from type IIa to type I in the EAMG group at the peak stage, as verified by histological and molecular analyses. Second-generation sequencing results predicted that the PI3K-Akt signaling pathway might be involved in the switch, and the mRNA expression levels of the PI3K-Akt pathway-related genesNr4a1, IL2rb, Col1A1 and Ddit4 were significantly different. In conclusion, this study indicates that the switch of muscle fiber subtypes in MG via the PI3K-Akt signaling pathway may be a potential target for the treatment of MG-related skeletal muscle atrophy in the future.

Temperature manipulation during incubation: effect on embryo development and incidence of white striping and expression of related genes in broiler chickens from two commercial breeds

1. This study evaluated the effects of cyclic eggshell temperature between 10 and 14 d of embryogenesis on traits viz. the expression of MYOZ2, PPARγ and GPx7 in breast muscle, meat quality and incidence of white striping at slaughter age.2. Eggs were obtained from Cobb and Ross broiler breeders to investigate the response of breeds to eggshell temperature, which regulated air temperature. A total of 784 eggs were incubated at either the control eggshell temperature (37.8°C) from 0 to 18 d or exposed to cyclic high eggshell temperature (CHT) at 38.8°C for 6 h/d between 10 and 14 d of incubation. The temperature was 36.8°C between 18 and 21 d. Hatched chicks were reared under optimum rearing conditions. The birds were sampled at 19 d of incubation, at hatch and at 42 d post-hatch.3. There was no effect of eggshell temperature on yolk-free body weight and residual yolk sac weight. The CHT chicks had wider breasts on the day of hatching.4. At hatch and 42d post-hatch, PPARγ expression in Cobb-CHT was upregulated 4.78-fold and downregulated 3.28-fold, respectively, compared to the Cobb-control. At slaughter age, chickens from Ross-CHT had 1.98- and 2.33-fold upregulated PPARγ and GPX7 expressions, respectively, compared to Ross-control. The CHT increased GPx7 expression in the Cobb-CHT day-old chicks compared to the Cobb-control. On ED19, MYOZ2 expression was upregulated in Cobb and downregulated in Ross by CHT.5. The effects of breed and eggshell temperature on pH15, L*, a*, expressible juice and cooking loss were not significant. The CHT increased the incidence of severe white striping lesions in Ross chickens.6. It was concluded eggshell temperature modulated embryo development, incidence of white striping and expression of related genes differently in the two commercial breeds.

Effect of fructo-oligosaccharides on growth performance and meat quality in broilers

This study investigated the fructo-oligosaccharides (FOS) on growth performance and meat quality in broilers. Total 160 Xianghuang broilers aged 2 months were randomly assigned into 2 groups, CON (control), FOS (supplemented 0.5% fructo-oligosaccharides in diet). After 38 days, the breast, thigh muscle and liver samples were collected for further analysis. Results showed that no significant effect of 0.5% FOS on growth performance such as average daily gain (ADG), average daily feed intake (ADFI) or feed-to-gain ratio (F:G) were observed (P > 0.05). Broilers in FOS group had a yellower breast than that in CON group (P < 0.05). Breast pH45min and thigh pH24h value of FOS group were greater than that in CON group (P < 0.05). Max shear force and work of shear of cooked breast (pectoralis major) muscle was lower in FOS group compared with CON group (P < 0.05). Hardness (P = 0.065), fracturability (P = 0.063), gumminess (P = 0.079), chewiness (P = 0.080) of cooked thigh meat tended to be higher in FOS group compared to the CON group. Addition of 0.5% FOS resulted in lower thigh total superoxide dismutase (T-SOD) activity compared to CON group (P < 0.05). The malonaldehyde (MDA) concentration (P = 0.066) of breast muscle tended to be lower in FOS group compared with CON group. There was an increasing trend for total antioxidant capacity (T-AOC) activity of thigh muscle in FOS group compared to CON group (P = 0.053). Relative mRNA expression of breast catalase (CAT), superoxide dismutase 1 (SOD1), thioredoxin reductase 1 (TXNRD) were up-regulated by FOS supplementation compared with CON group (P < 0.05). In conclusion, FOS can be utilized at 0.5 % to improve meat quality such as elevating pH value, yellowness and decreasing max shear force of muscle through enhancing the antioxidant activity in broilers.

Genome-wide association study of myofiber type composition traits in a yellow-feather broiler population

Meat quality is a key factor determining the economic viability of the broiler industry, particularly in native broiler breeds. Skeletal muscles contain a mixture of muscle fibers, each possessing unique physicochemical properties; the composition of myofiber types within these muscles is closely linked to meat quality. However, comprehension of the regulatory mechanisms governing this trait remains limited. Therefore, we conducted a genome-wide association study (GWAS) with a population of 400 yellow-feather broilers to explore genetic variations associated with myofiber-type composition at the genomic level. Whole-genome resequencing was employed to detect genetic variations and immunohistochemistry was used for muscle fiber typing in the sartorius muscle. We identified 1 and 18 single-nucleotide polymorphisms (SNPs) significantly and potentially associated with the proportion of slow muscle fibers, respectively, and 1 and 12 SNPs significantly and potentially associated with the area proportion of slow muscle fibers, respectively. We annotated several candidate genes, including DMD, KLF7, CREB1, EFCAB11, GADD45A, GSTT1, and GSTT1L, which are related to myofiber type composition. We also demonstrated that myofiber composition traits exhibit low-to-medium heritability, indicating potential for enhancement through genetic selection. These findings provide a crucial reference for further studies on the regulatory mechanisms of poultry meat quality and for advancing the breeding of superior-quality broiler chickens.

Comparative Analysis of Myofiber Characteristics, Shear Force, and Amino Acid Contents in Slow- and Fast-Growing Broilers

Skeletal muscle fiber characteristics are pivotal in assessing meat quality. However, there is currently a lack of research precisely quantifying the total number of myofibers (TNM) of skeletal muscles. This study used Arbor Acres (AA) broilers and Wenchang (WC) chickens to determine the TNM of several skeletal muscles and the meat quality of the pectoralis major muscle (PM). The results showed that the TNMs of the PM in AA males and females were 935,363.64 ± 92,529.28 and 873,983.72 ± 84,511.28, respectively, significantly higher than those in WC (511,468.97 ± 73,460.81 and 475,371.93 ± 70,187.83) at 7 days of age (p < 0.01). In terms of gastrocnemius medialis in AA males and females, we recorded values of 207,551.43 ± 31,639.97 and 177,203.23 ± 28,764.01, showing a significant difference compared to the values observed in WC (146,313.03 ± 29,633.21 and 124,238.9 ± 20,136.95) (p < 0.01). Similarly, the levels of gastrocnemius lateralis exhibited a significant difference between AA and WC (p < 0.01). Furthermore, the essential, umami, and sweet amino acids were found to be significantly higher in WC compared to AA (p < 0.01). These findings offer valuable data and insights for accurately quantifying the TNM in livestock and for the development of further genetic breeding strategies for meat quality.

METTL16 inhibits differentiation and promotes proliferation and slow myofibers formation in chicken myoblasts

N6-methyladenosine (m6A) plays a crucial regulatory role in muscle growth and development. In our previous studies, we identified a m6A methyltransferase, Methyltransferase like 16 (METTL16), which is associated with chicken muscle development and muscle fiber type conversion. To further understand the regulatory role of METTL16 in chicken muscle function, we analyzed its expression in muscle tissues with different myofiber type compositions and in chicken primary myoblasts (CPMs) at various stages. We also manipulated METTL16 expression in CPMs to examine its effects on cell proliferation, differentiation, muscle fiber type formation, and global m6A RNA methylation status. Our results showed that METTL16 expression increased during myoblast proliferation and gradually decreased in the late differentiation stage. Furthermore, METTL16 exhibited specific expression in slow-twitch muscles. Cell Counting Kit-8 assays, 5-Ethynyl-2'-deoxyuridine staining, RT-qPCR, Western blot, and immunofluorescence analyses showed that METTL16 promotes myoblast proliferation while inhibiting myoblast differentiation. We also observed that METTL16 induces the upregulation of slow-twitch myosin heavy chain (MyHC) and slow-twitch-specific genes in myotubes, while downregulating fast-twitch MyHC and fast-twitch-specific genes. Furthermore, both interference and overexpression of METTL16 led to changes in overall cellular m6A modification levels and Methyltransferase like 3 (METTL3) expression levels. These findings confirm that METTL16 plays a key role in myoblast proliferation, differentiation, and muscle fiber type formation in chickens. Considering the role of myoblasts in chicken muscle growth and meat quality regulation, METTL16 may serve as a key target for molecular selection in chicken meat traits.

Dietary Bacillus subtilis benefits meat quality by regulating the muscle fiber type and antioxidant capacity of broilers

The effects of dietary Bacillus subtilis (BS) on the meat quality of broilers were evaluated, with an emphasis on the regulation of muscle fiber types and antioxidant capabilities. One hundred and forty-four Arbor Acres male broilers were divided into 3 treatment groups (0, 300 mg/kg and 500 mg/kg dietary BS) and raised for 35 d. The results suggested that BS improved meat quality by improving the muscular pH, meat color, water holding capacity and shear force. Immunofluorescence staining revealed a positive impact of BS on the muscle fiber transformation in thigh muscles, and the gene/protein expression data from specific muscle fiber types confirmed this finding. BS activated AMP-activated protein kinase (AMPK), silent information regulator 1 and peroxisome proliferator-activated receptor gamma coactivator 1alpha. The postmortem analysis revealed that BS increased the activity of glutathione peroxidase and total antioxidant capacity while decreasing the malondialdehyde content. Additionally, BS increased the gene and protein expression of nuclear factor-like 2 (Nrf2) and activated the Nrf2 signaling pathway, including its downstream factors, such as heme oxygenase-1, catalase, superoxide dismutase and glutathione peroxidase. In conclusion, dietary BS improved meat quality by modifying muscle fiber types and enhancing the antioxidant capacity in broilers.

Metabolomic profiles and compositional differences involved in flavor characteristics of raw breast meat from slow- and fast-growing chickens in Thailand

This study aimed to differentiate the flavor characteristics of raw chicken breast meat from Thai slow-growing breeds (NC: native chicken, and KC: Korat/crossbred chicken) and fast-growing broilers (BR: broiler chicken) by using NMR-based metabolomic approaches along with multivariate data analysis. Chemical compounds related to chicken's flavor including free amino acids (FAA), ATP and its related compounds, sugars, as well as volatile compounds (VOC), were also investigated. BR had the highest total FAAs, followed by NC and KC (P < 0.05). In contrast, the accumulations of ATP degradation products, particularly ADP and IMP, were found at higher levels in the NC and KC (P < 0.05), while the highest total reducing sugars were noted in the KC (P < 0.05). Most VOCs found in the fresh breasts were products from the degradation of lipids, especially through lipid oxidation, which was found in varied types and proportions among samples. Not only chemical compounds but varying amounts of metabolites among samples were also detected. Apart from 21 identified metabolites, Glu, Gln, and betaine were the most prevalent in all samples with VIP > 1.00. Among 19 metabolic pathways, the most important pathways (P-value < 0.05, FDR < 0.05, impact > 0.05) were discovered to differentiate the flavor of raw chicken breast meat from various breeds. These metabolic pathways included (1) Ala, Asp and Glu metabolism; (2) D-Gln and D-Glu metabolism; (3) Purine metabolism; (4) β-Ala metabolism; (5) Aminoacyl-tRNA biosynthesis; (6) Nicotinate and nicotinamide metabolism; (7) Pyrimidine metabolism. Interestingly, based on the principal component analysis plot and partial least square-discriminant analysis (R2 = 0.9804; Q2 = 0.9782), NC and KC were clustered in the same area and discriminated from BR, indicating their similar flavor characteristics and metabolic profiles. Therefore, the findings could comprehend and distinguish the flavor of chicken breast meat of slow- from fast-growing chicken breeds based on their chemical characteristics and metabolite profiles.

Skeletal muscle metabolic characteristics and fresh meat quality defects associated with wooden breast

Wooden breast (WB) is a myopathy that occurs in pectoralis major (PM) muscles, predominately affecting large, fast-growing broilers. Severe myodegeneration, increased hypoxia, reduced blood flow, and increased collagen deposition are hallmark characteristics of WB that culminate in unsatisfactory fresh meat quality attributes, such as poor water-holding capacity, tenderness, and processing characteristics. Therefore, WB meat is often downgraded resulting in economic losses for the United States poultry industry. Although WB has been well characterized, its etiology remains undefined. As the scientific community continues to resolve mechanisms responsible for WB onset, understanding biochemical changes associated with WB may facilitate solutions to negate its poor meat quality attributes. Given changes in metabolism of living muscle can alter biochemical processes during the conversion of muscle to meat, this review aims to summarize and discuss the current knowledge of WB muscle and meat biochemistry. For example, it appears metabolic pathways that support combating stress are upregulated in WB muscle at the expense of glycolytic flux, which presumably contributes to the high ultimate pH of WB meat. Further, perturbed function of WB mitochondria, such as altered calcium handling, impacts aspects of postmortem metabolism and proteolysis. Collectively, metabolic dysfunction of WB muscle alters the biochemical processes that occur during the conversion of muscle to meat, and thus contributes to the poor WB meat quality.

Evaluation of the Growth Performance and Meat Quality of Different F1 Crosses of Tengchong Snow and Xichou Black Bone Chicken Breeds

Unlike other chicken breeds, Xichuan Black Bone (XBB) chickens are an established breed in China with excellent production performance and unique characteristics, including black meat, beaks, skin, bones, and legs, and they produce blue-shelled eggs. The Tengchong Snow (TS) chicken breed has relatively lower growth performance than commercial breeds but is considered one of the main genetic treasures of black meat in China. To improve the production and meat quality traits of the TS chickens by hybridization, the current study aimed to investigate the growth performance, carcass indices, meat quality physical properties, and muscle fiber traits of fiber traits of F1 crosses of TS with XBB chickens. Three groups of crossbreeding combinations were produced: (1) XT group (XBB × TS ), (2) TX group (TS × XBB ), and (3) TT group (TS × TS ), with the TT group used as a control. A total of 725 healthy chicks (XT group: 247, TX group: 180, TT group: 298) were reared up to 20 weeks of age to estimate the growth performance and associated meat parameters. The results showed that the XT and TX groups had higher body weight and body size compared with the TT group (p < 0.05). Similarly, breast width, breast length, width of body, and carcass weights were also greater (p < 0.05) in the XT and TX groups compared with the TT group. Meat physical properties, including color, water-holding capacity, and tenderness, were improved (p < 0.05) for the XT and TX group compared to the TT group. The XT group had the better color of the leg muscles with the unique orientation of muscle fibers. Based on the results, the XT group is more in line with the future breeding direction as they have greater body weight, larger size, and lower abdominal fat. This study is a baseline technical reference for the protection, evaluation, and utilization of germplasm resources of Tengchong Snow chicken for screening the best matching lines and combinations with local chickens.

Effect of myristic acid supplementation on triglyceride synthesis and related genes in the pectoral muscles of broiler chickens

Fatty acids (FAs) can serve as energy for poultry, maintain normal cell structure and function, and support a healthy immune system. Although the addition of polyunsaturated fatty acids (PUFAs) to the diet has been extensively studied and reported, the mechanism of action of saturated fatty acids (SFAs) remains to be elucidated. We investigated the effect of 0.04% dietary myristic acid (MA) on slaughter performance, lipid components, tissue FAs, and the transcriptome profile in chickens. The results showed that dietary MA had no effect on slaughter performance (body weight, carcass weight, eviscerated weight, and pectoral muscle weight) (P > 0.05). Dietary MA enrichment increased MA (P < 0.001) and triglycerides (TGs) (P < 0.01) levels in the pectoral muscle. The levels of palmitic acid, linoleic acid (LA), arachidonic acid (AA), SFAs, monounsaturated fatty acids (MUFAs), and PUFAs were significantly higher (P < 0.01) in the MA supplementation group compared to the control group. However, there were no significant differences in the ratios of PUFA/SFA and n6/omega-3 (n3) between the two groups. The MA content was positively correlated with the contents of palmitic acid, LA, linolenic acid (ALA), n3, n6, SFAs, and unsaturated fatty acids (UFA). DHCR24, which is known to be involved in steroid metabolism and cholesterol biosynthesis pathways, was found to be a significantly lower in the MA supplementation group compared to the control group (P < 0.05, log2(fold change) = -0.85). Five overlapping co-expressed genes were identified at the intersection between the differential expressed genes and Weighted Gene Co‑expression Network Analysis-derived hub genes associated with MA phenotype, namely BHLHE40, MSL1, PLAGL1, SRSF4, and ENSGALG00000026875. For the TG phenotype, a total of 28 genes were identified, including CHKA, KLF5, TGIF1, etc. Both sets included the gene PLAGL1, which has a negative correlation with the levels of MA and TG. This study provides valuable information to further understand the regulation of gene expression patterns by dietary supplementation with MA and examines at the molecular level the phenotypic changes induced by supplementation with MA.

Insights into the evaluation, influential factors and improvement strategies for poultry meat quality: a review

Poultry meat, an essential source of animal protein, requires stringent safety and quality measures to address public health concerns and growing international attention. This review examines both direct and indirect factors that compromise poultry meat quality in intensive farming systems. It highlights the integration of rapid and micro-testing with traditional methods to assess meat safety. The paper advocates for adopting probiotics, prebiotics, and plant extracts to improve poultry meat quality.

Research progress on regulating factors of muscle fiber heterogeneity in poultry: a review

Control of meat quality traits is an important goal of any farm animal production, including poultry. A better understanding of the biochemical properties of muscle fiber properties that drive muscle development and ultimately meat quality constitutes one of the major challenging topics in animal production and meat science. In this paper, the existing classification methods of skeletal muscle fibers in poultry were reviewed and the relationship between contractile and metabolic characteristics of muscle fibers and poultry meat quality was described. Finally, a comprehensive review of multiple potential factors affecting muscle fiber distribution and conversion is presented, including breed, sex, hormones, growth performance, diet, muscle position, exercise, and ambient temperature. We emphasize that knowledge of muscle fiber typing is essential to better understand how to control muscle characteristics throughout the life cycle of animals to better manage the final quality of poultry meat.

Effect of Early Ciprofloxacin Administration on Growth Performance, Meat Quality, Food Safety, and Metabolomic Profiles in Xueshan Chickens

To investigate the effects of early administration of ciprofloxacin (CIP) on Xueshan chickens, in this study Xueshan chickens were measured for growth performance, tested for drug residues, evaluated for meat quality, and muscle metabolism changes were explored using a non-target metabolomics approach. Experimental findings revealed that early CIP use did not significantly impact the overall growth rate of Xueshan chickens (p > 0.05). However, notable alterations in meat quality were observed: the CIP-treated group exhibited a significant decrease in muscle pH (pH1 and pH24) and a marked increase in drip loss and moisture content (p > 0.05). No CIP residues were detected in muscle tissue. Untargeted metabolomics analyses unveiled significant alterations in the metabolic profile of market-age chickens following CIP treatment. Both functional enrichment and metabolic network analyses indicated significant effects on the ko01120 (microbial metabolism in diverse environments) and ko00350 (tyrosine metabolism) pathways, implying that CIP treatment may influence chicken meat quality by modulating microbial communities and amino acid metabolism. This study provides a crucial foundation for understanding the impact of antibiotics on meat quality and metabolism in poultry production, offering scientific insights for optimizing antibiotic-use strategies and safeguarding poultry product quality.

Transcriptome analysis reveals the synergistic involvement of MGLL and LPIN1 in fatty acid synthesis in broiler pectoral muscles

Fatty acids (FAs) are one of the most important bioactive compounds affecting the quality of meat. In this study, we compared the expression profiles of genes involved in FA production in the breast muscle of Jingxing Yellow chickens at different days of age determined by transcriptomic analysis to identify key genes and pathways regulating the FA composition of the breast muscle. Through clustering analysis of gene expression data, the growth process of broiler chickens can be divided into two stages, namely the growth and development stage at the 35th and 63rd days of age (D35, D63), and the mature stage at the 119th day of age (D119). The content of some important unsaturated fatty acids (UFAs), such as C18:2n6c, C20:4n6, and C22:6n3, in the pectoral muscles, differed significantly between these two stages (p < 0.05). Therefore, we compared the gene expression profiles at D35 and D63 with those at D119, and identified differentially expressed genes (DEGs). The gene modules related to the five UFAs with significant changes were identified by weighted gene co-expression network analysis (WGCNA), and then 150 crossover genes were identified by crossover analysis of the detected DEGs and WGCNA. The results of the pathway enrichment analysis revealed the glycerolipid metabolism pathway related to lipid metabolism, in which the MGLL and LPIN1 genes were particularly enriched. In this study, the expression levels of MGLL and LPIN1 showed an increasing trend during the growth process of broilers, with a negative regulatory effect on the significantly reduced content of C18:2n6c in the pectoral muscle, and a positive regulatory effect on the significantly increased content of C20:4n6. These findings indicated that MGLL and LPIN1 synergistically promote the deposition of FAs, which may further promote the conversion of linoleic acid (C18:2n6c) to arachidonic acid (C20:4n6). Therefore, screening and identifying FA production-related functional genes are key to elucidate the regulatory molecular mechanism of production of FAs in chicken muscle, aiming to provide a theoretical basis for improving chicken meat quality.

Identification of relevant differential genes to the divergent development of pectoral muscle in ducks by transcriptomic analysis

OBJECTIVE

The objective of this study was to identify candidate genes that play important roles in skeletal muscle development in ducks.

METHODS

In this study, we investigated the transcriptional sequencing of embryonic pectoral muscles from two specialized lines: Liancheng white ducks (female) and Cherry valley ducks (male) hybrid Line A (LCA) and Line C (LCC) ducks. In addition, prediction of target genes for the differentially expressed mRNAs was conducted and the enriched gene ontology (GO) terms and Kyoto encyclopedia of genes and genomes signaling pathways were further analyzed. Finally, a protein-to-protein interaction network was analyzed by using the target genes to gain insights into their potential functional association.

RESULTS

A total of 1,428 differentially expressed genes (DEGs) with 762 being up-regulated genes and 666 being down-regulated genes in pectoral muscle of LCA and LCC ducks identified by RNA-seq (p<0.05). Meanwhile, 23 GO terms in the down-regulated genes and 75 GO terms in up-regulated genes were significantly enriched (p<0.05). Furthermore, the top 5 most enriched pathways were ECM-receptor interaction, fatty acid degradation, pyruvate degradation, PPAR signaling pathway, and glycolysis/gluconeogenesis. Finally, the candidate genes including integrin b3 (Itgb3), pyruvate kinase M1/2 (Pkm), insulinlike growth factor 1 (Igf1), glucose-6-phosphate isomerase (Gpi), GABA type A receptorassociated protein-like 1 (Gabarapl1), and thyroid hormone receptor beta (Thrb) showed the most expression difference, and then were selected to verification by quantitative realtime polymerase chain reaction (qRT-PCR). The result of qRT-PCR was consistent with that of transcriptome sequencing.

CONCLUSION

This study provided information of molecular mechanisms underlying the developmental differences in skeletal muscles between specialized duck lines.

Nano-Se exhibits limited protective effect against heat stress induced poor breast muscle meat quality of broilers compared with other selenium sources

BACKGROUND

At present, heat stress (HS) has become a key factor that impairs broiler breeding industry, which causes growth restriction and poor meat quality of broilers. Selenium (Se) is an excellent antioxidant and plays a unique role in meat quality improvement. Recent years, nano-selenium (NanoSe) has received tremendous attention in livestock production, due to its characteristic and good antibacterial performance in vitro. Here, we developed the heat stressed-broiler model to investigate the protective effects of NanoSe on growth performance and meat quality of broilers and compare whether there are differences with that of other Se sources (Sodium selenite, SS; Selenoyeast, SeY; Selenomethionine, SeMet).

RESULTS

HS jeopardized the growth performance and caused poor meat quality of breast muscle in broilers, which were accompanied by lowered antioxidant capacity, increased glycolysis, increased anaerobic metabolism of pyruvate, mitochondrial stress and abnormal mitochondrial tricarboxylic acid (TCA) cycle. All Se sources supplementation exhibited protective effects, which increased the Se concentration and promoted the expression of selenoproteins, improved the mitochondrial homeostasis and the antioxidant capacity, and promoted the TCA cycle and the aerobic metabolism of pyruvate, thus improved the breast muscle meat quality of broilers exposed to HS. However, unlike the other three Se sources, the protective effect of NanoSe on meat quality of heat stressed-broilers was not ideal, which exhibited limited impact on the pH value, drip loss and cooking loss of the breast muscle. Compared with the other Se sources, broilers received NanoSe showed the lowest levels of slow MyHC, the highest levels of fast MyHC and glycogen, the highest mRNA levels of glycolysis-related genes (PFKM and PKM), the highest protein expression of HSP60 and CLPP, and the lowest enzyme activities of GSH-Px, citroyl synthetase (CS) and isocitrate dehydrogenase (ICD) in breast muscle. Consistent with the SS, the Se deposition in breast muscle of broilers received NanoSe was lower than that of broilers received SeY or SeMet. Besides, the regulatory efficiency of NanoSe on the expression of key selenoproteins (such as SELENOS) in breast muscle of heat stressed-broilers was also worse than that of other Se sources.

CONCLUSION

Through comparing the meat quality, Se deposition, muscle fiber type conversion, glycolysis, mitochondrial homeostasis, and mitochondrial TCA cycle-related indicators of breast muscle in heat stressed broilers, we found that the protective effects of organic Se (SeY and SeMet) are better than that of inorganic Se (SS) and NanoSe. As a new Se source, though NanoSe showed some protective effect on breast muscle meat quality of heat stressed broilers, the protective effect of NanoSe is not ideal, compared with other Se sources.

Transcriptomic and epigenomic landscapes of muscle growth during the postnatal period of broilers

BACKGROUND

Broilers stand out as one of the fastest-growing livestock globally, making a substantial contribution to animal meat production. However, the molecular and epigenetic mechanisms underlying the rapid growth and development of broiler chickens are still unclear. This study aims to explore muscle development patterns and regulatory networks during the postnatal rapid growth phase of fast-growing broilers. We measured the growth performance of Cornish (CC) and White Plymouth Rock (RR) over a 42-d period. Pectoral muscle samples from both CC and RR were randomly collected at day 21 after hatching (D21) and D42 for RNA-seq and ATAC-seq library construction.

RESULTS

The consistent increase in body weight and pectoral muscle weight across both breeds was observed as they matured, with CC outpacing RR in terms of weight at each stage of development. Differential expression analysis identified 398 and 1,129 genes in the two dimensions of breeds and ages, respectively. A total of 75,149 ATAC-seq peaks were annotated in promoter, exon, intron and intergenic regions, with a higher number of peaks in the promoter and intronic regions. The age-biased genes and breed-biased genes of RNA-seq were combined with the ATAC-seq data for subsequent analysis. The results spotlighted the upregulation of ACTC1 and FDPS at D21, which were primarily associated with muscle structure development by gene cluster enrichment. Additionally, a noteworthy upregulation of MUSTN1, FOS and TGFB3 was spotted in broiler chickens at D42, which were involved in cell differentiation and muscle regeneration after injury, suggesting a regulatory role of muscle growth and repair.

CONCLUSIONS

This work provided a regulatory network of postnatal broiler chickens and revealed ACTC1 and MUSTN1 as the key responsible for muscle development and regeneration. Our findings highlight that rapid growth in broiler chickens triggers ongoing muscle damage and subsequent regeneration. These findings provide a foundation for future research to investigate the functional aspects of muscle development.

Skeletal Muscle Metabolism Is Dynamic during Porcine Postnatal Growth

Skeletal muscle metabolism has implications for swine feed efficiency (FE); however, it remains unclear if the metabolic profile of skeletal muscle changes during postnatal growth. To assess the metabolic changes, samples were collected from the longissimus dorsi (LD, glycolytic muscle), latissimus dorsi (LAT, mixed muscle), and masseter (MS, oxidative muscle) at 20, 53, 87, 120, and 180 days of age from barrows. Muscles were assessed to determine the abundance of several metabolic enzymes. Lactate dehydrogenase (LDHα) decreased in all muscles from 20 to 87 d (p < 0.01), which may be attributed to the muscles being more glycolytic at weaning from a milk-based diet. Pyruvate carboxylase (PC) increased in all muscles at 53 d compared to the other time points (p < 0.01), while pyruvate dehydrogenase α 1 (PDHα1) increased at 87 and 180 d in MS compared to LD (p < 0.05), indicating that potential changes occur in pyruvate entry into the tricarboxylic acid (TCA) cycle during growth. Isolated mitochondria from each muscle were incubated with 13C-labeled metabolites to assess isotopomer enrichment patterns of TCA intermediates. Citrate M + 2 and M + 4 derived from [13C3]-pyruvate increased at 87 d in LAT and MS mitochondria compared to LD mitochondria (p < 0.05). Regardless of the muscle, citrate M+3 increased at 87 d compared to 20, 53, and 120 d, while 180 d showed intermediate values (p < 0.01). These data support the notion that pyruvate metabolism is dynamic during growth. Our findings establish a metabolic fingerprint associated with postnatal muscle hypertrophy.

Effects of Sex on Growth Performance, Carcass Traits, Blood Biochemical Parameters, and Meat Quality of XueShan Chickens

The demand for high-quality chilled chicken has continued to increase in China. Chickens are sexually dimorphic, and to better understand the specific differences in chicken production based on sex, we examined how sex affects growth performance, carcass traits, and meat quality of yellow-feathered chickens. Male and female Xueshan chickens were used as the experimental model. Although males exhibited better growth performance, including body weight (BW), body slope, keel, shank length, and shank girth (p < 0.05), as well as carcass traits, such as dressed weight, leg muscle, and lean meat, females had higher carcass and breast muscle yields (p < 0.05). Males had higher follicle density and yellowness (b*) of the skin and better skin than females (p < 0.05). Among blood biochemical parameters, the serum content of corticosterone (CORT) was higher in males, while those of superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), total antioxidant capacity (T-AOC), and catalase (CAT) were lower in males than in females (p < 0.05). The pH levels, shear force, and moisture content quality were better in male breast meat, while the intramuscular fat content (IMF) was lower in males than in females (p < 0.05). The redness (a*) and moisture content were higher in male leg meat, while the pH, water-loss rate (WLR), lightness (L*), and IMF were lower (p < 0.05). The muscle fiber diameter and cross-sectional area were also higher in males (p < 0.05). Consumers felt that soup of male chicken was better than female (p < 0.05), while mouthfeel and tenderness acceptance of breast meat were different between the sexes. These results indicate that female chickens can be marketed as a whole carcass, while males are more suitable for processed carcass products. This study provides significant insights into the production and processing methodologies of yellow-feathered chickens.

Neurophysiology of the Superior Laryngeal Nerve in an In Vivo Rat Model

OBJECTIVE

The superior laryngeal nerve (SLN) is fundamental in laryngeal sensation, cough reflex, and pitch control. SLN injury has substantial consequences including altered sensation, aspiration, and dysphonia. To date, in vivo measurement of the SLN remains elusive. The purpose of this study was to assess the feasibility of recording motor and sensory evoked potentials in a rat SLN model.

METHODS

Twenty-two rat hemi-laryngeal preparations (n = 11) were obtained from 4-month-old Sprague-Dawley rats and included in this study. Compound motor action potentials (CMAPs) and motor unit number estimation (MUNE) were calculated by stimulating the SLN at the point of medial extension near the carotid artery and by placing a recording electrode on the cricothyroid muscle. Sensory response was determined through stimulation of the SLN and laryngoscopic visualization of a laryngeal adductor reflex (LAR). SLN and cricothyroid muscle cross-sections were stained and histologic morphometrics were quantified.

RESULTS

Laryngeal evoked potentials were successfully obtained in all trials. Mean CMAP latency and negative durations were 0.99 ± 0.57 ms and 1.49 ± 0.57 ms, respectively. The median MUNE was 2.06 (IQR 1.88, 3.51). LAR was induced with a mean intensity of 0.69 ± 0.20 mV. Mean axon count, myelin thickness, and g-ratio were 681 ± 192.2, 1.72 ± 0.26, and 0.45 ± 0.04, respectively.

CONCLUSIONS

This study demonstrates the feasibility of recording evoked response potentials following SLN stimulation. We hypothesize that this work will provide a tractable animal model to study changes in laryngeal sensation and cricothyroid motor function with aging, neurodegenerative disease, aspiration, or nerve injury.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:1778-1784, 2024.

Transcriptome Data Revealed the circRNA-miRNA-mRNA Regulatory Network during the Proliferation and Differentiation of Myoblasts in Shitou Goose

CircRNA, a recently characterized non-coding RNA (ncRNA) variant, functions as a molecular sponge, exerting regulatory control by binding to microRNA (miRNA) and modulating the expression of downstream proteins, either promoting or inhibiting their expression. Among poultry species, geese hold significant importance, prized by consumers for their delectable taste and rich nutritional content. Despite the prominence of geese, research on the growth and development of goose muscle, particularly the regulatory role of circRNAs in goose muscle formation, remains insufficiently explored. In this study, we constructed comprehensive expression profiles of circRNAs and messenger RNAs (mRNAs) within the myoblasts and myotubes of Shitou geese. We identified a total of 96 differentially expressed circRNAs (DEcircRNAs) and 880 differentially expressed mRNAs (DEmRNAs). Notably, the parental genes of DEcircRNAs and DEmRNAs exhibited enrichment in the Wnt signaling pathway, highlighting its potential impact on the proliferation and differentiation of goose myoblasts. Employing RNAhybrid and miRDB, we identified circRNA-miRNA pairs and mRNA-miRNA pairs that may play a role in regulating myogenic differentiation or muscle growth. Subsequently, utilizing Cytoscape, we constructed a circRNA-miRNA-mRNA interaction network aimed at unraveling the intricate regulatory mechanisms involved in goose muscle growth and development, which comprises 93 circRNAs, 351 miRNAs, and 305 mRNAs. Moreover, the identification of 10 hub genes (ACTB, ACTN1, BDNF, PDGFRA, MYL1, EFNA5, MYSM1, THBS1, ITGA8, and ELN) potentially linked to myogenesis, along with the exploration of their circRNA-miRNA-hub gene regulatory axis, was also conducted. These competitive endogenous RNA (ceRNA) regulatory networks elucidate the molecular regulatory mechanisms associated with muscle growth in Shitou geese, providing deeper insights into the reciprocal regulation of circRNA, miRNA, and mRNA in the context of goose muscle formation.

Enhancing skeletal muscle fiber characteristics, intramuscular fat deposition, and fatty acid composition in broilers under heat stress through combined selenomethionine and Bacillus subtilis supplementation in the diet

Heat stress is the most common environmental stressor in poultry production, negatively affecting growth performance, meat quality, and welfare. Therefore, the aim of this study was to compare the nutritional effects of dietary supplementation with selenomethionine, Bacillus subtilis (BS), and a combination of selenomethionine and BS on broilers challenged with heat stress. A total of 300 21-day-old male broilers (Ross 308) were randomly assigned to 5 groups with 6 replicates of 10 broilers per each: control group (CON, broilers raised at 22 ± 2 °C), heat stress exposure group (HS, broilers raised at 32 ± 2 °C for 8 h/d), HSS group (HS group supplemented with 0.3 mg/kg selenomethionine), HSB group (HS group supplemented with 1 × 109 cfu/kg BS), and HSBS group (HS group supplemented with 0.3 mg/kg selenomethionine and × 109 cfu/kg BS). The experiment lasted for 21 d. The results indicated that, compared to the CON group, heat stress reduces (P < 0.05) broiler growth performance and damages the meat quality in breast and thigh muscles. Dietary supplementation with selenomethionine and BS did not improve the growth performance of broilers under heat stress. However, compared to the HS group, the HSS, HSB, and HSBS groups showed significantly increased (P < 0.05) pH45 min, redness (a*) and yellowness (b*), muscle fiber density, intramuscular fat, triglyceride content, and expression levels of Myf5, CAPN 2, FM, SLC27A1, A-FABP, H-FABP, APOB-100, and ACC in breast and thigh muscles. Meanwhile, these groups showed reduced (P < 0.05) lightness (L*), drip loss, shear force, muscle fiber cross-sectional area, and FM gene expression level. The HSBS group showed greater improvement in the physicochemical quality of muscle and volatile substances compared to the HSS and HSB groups. In conclusion, selenomethionine and BS improved meat quality and flavor in broilers under heat stress by modulating muscle fiber composition and characteristics, as well as increasing intramuscular fat deposition.

Comparison of muscle fiber characteristics and meat quality between newborn and adult Haimen goats

Goat meat is popular with consumers for its rich nutritional content. Muscle fiber characteristics have been shown to play a crucial role in determining the quantity and quality of meat. However, little is known about the temporal changes in muscle fiber characteristics and meat quality during growth in goats. In this study, muscle fiber type, fiber diameter, fiber cross-sectional area (CSA), glycolytic potential (GP), meat pH, and meat color were analyzed in the gastrocnemius (GAS), gluteus medius (GM), biceps brachii (BB), longissimus lumborum (LL) muscles from newborn (NHMG) and adult (AHMG) Haimen goats. The distribution of type I and type Π fiber in goats is not consistent across the four muscles and undergoes alterations with age. The diameter and CSA of the muscle fibers were similar among the four NHMG muscles. However, in AHMG, the LL muscle had the largest fiber in terms of both diameter and CSA, followed by BB, GM, and GAS muscles. Moreover, the CSA of type Π fibers was higher than that of type I fibers in both NHMG and AHMG. GP values ranged from 90 to 140 umol/g across the muscle and no significant differences were observed. AHMG had a higher pH level and a* value, but lower L* and b* values than NHMG. Overall, our findings enhance our understanding of the changes in muscle fiber type and meat quality during the growth in Haimen goats and provide a basis for future research on the development and transformation of muscle fibers in goats.

Effects of genetic selection for fast growth on the development of wooden breast myopathy in broilers

1. This study investigated the physiological and molecular mechanisms leading to wooden breast (WB) by comparing growth parameters, oxygen consumption rate, thyroid hormone and gene expression patterns in fast- versus slow-growing broiler lines (Cobb500 and L1986, respectively).2. WB was observed in Cobb500 broilers only and was first diagnosed on d 21 post-hatch. Compared to the slow-growing L1986, Cobb500 showed a significantly higher growth rate, relative breast weight, breast thickness, meat pH and water-retention capacity (drip loss). Correspondingly, there was significantly lower relative heart weight, relative right ventricular weight, triiodothyronine and thyroxine concentrations and oxygen consumption rate.3. Compared to No-WB Cobb500, the WB-affected samples exhibited higher relative breast weight, breast thickness and drip loss and lower plasma total thyroxine (T4) concentrations.4. Selection for fast growth was associated with differential expression of genes involved in hypoxia (PLOD2), energy metabolism (FABP3, FABP4, CD36, and LPL), endoplasmic reticulum stress, muscle regeneration (CSRP3) and fibre-type switching (ANKRD1). WB-affected samples exhibited an upregulation of CSRP3, PLOD2 and ANKRD1, while CD36 was downregulated. Taken together, selection for fast growth and muscle gain is not matched by adequate cardiac and metabolic support systems.

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.

Developmental Characteristics of Skeletal Muscle during the Embryonic Stage in Chinese Yellow Quail (Coturnix japonica)

The quail is an important research model, and the demand for quail meat has been increasing in recent years; therefore, it is worthwhile investigating the development of embryonic skeletal muscle and the expression patterns of regulatory genes. In this study, the expression of MyoD and Pax7 in the breast muscle (m. pectoralis major) and leg muscle (m. biceps femoris) of quail embryos on days 10 through 17 were determined using qRT-PCR. Paraffin sections of embryonic muscle were analyzed to characterize changes over time. Results showed that MyoD and Pax7 were expressed in both breast and leg muscles and played a significant role in embryonic muscle development. Compared to breast muscle, leg muscle grew faster and had greater weight and myofiber size. The findings suggested that embryonic day 12 (E12) may be a key point for muscle development. Correlation analysis showed that MyoD expression was significantly negatively correlated with muscle and embryo weight, whereas Pax7 gene expression had no significant correlation with these characteristics. These fundamental results provide a theoretical basis for understanding the characteristics and transition points of skeletal muscle development in quail embryos and an important reference for farmers raising quail from eggs.

The Energy and Nutritional Value of Meat of Broiler Chickens Fed with Various Addition of Wheat Germ Expeller

The study concerns the effect of wheat germ expeller (WGE) as a feed additive given to male Ross-308 broiler chickens on their meat's energy and nutritional value, and coverage of nutrient reference values-requirements (NRV-R) of consumers for particular minerals. The chickens in the control group (CT-Control Treatment) were fed a standard complete mix. The experimental groups (EX5, EX10, EX15) were given a feed in which wheat middling was replaced with 5, 10, and 15% WGE. The breast and thigh muscles of 32 randomly selected chickens (8 in each group) were analyzed. More water, crude protein, P, Mg, Fe, Cu, and Mn were determined in the breast muscles, and more crude fat, crude ash, Ca, and Zn in the thigh muscles. Chickens from the CT group consumed significantly (p ≤ 0.01) less feed per body weight than those from groups EX5 to EX15, but achieved the highest body weight per 100 g of consumed feed. A higher (p ≤ 0.01) feed, energy, crude protein, and crude fat intake was observed in groups EX5 to EX15 compared to CT. The higher (p ≤ 0.01) value of protein efficiency ratios was indicated in the CT group. The WGE additive did not impact the muscles' energy values but affected the nutritional value. The daily consumption of 100 g of breast muscles to a large extent covers the consumer NRV-R for P, Mg Fe, Cu, and Mn. However, thigh muscles cover the NRV-R to a greater extent for Ca and Zn. The EX15, EX5, and EX10 muscles covered most of the NRV-R for P, Ca, and Mg, while the CT muscles did the same for Zn and Mn. Adding 5% WGE to broiler feed is optimal as it does not impair the nutritional value of the muscles.

Comparison of meat quality and glycolysis potential of two hybrid pigs in three-way hybrid model

With the improvement of consumers' requirements for pork quality, the method of crossbreeding with excellent local pig breeds to improve meat quality is popular. Saba pig has high reproduction rate, good meat quality and high utilization rate of roughage, but its excellent characteristics have not been fully developed and utilized. To promote the development and utilization of Saba pigs and production of high-quality pork, the meat quality traits and glycolysis potential of Duroc × (Landrace × Yorkshire) (DLY), Berkshire × (Duroc × Saba) (BDS), and Duroc × (Berkshire × Saba) (DBS) three-way crossbred pigs were compared. The results showed that DLY had the highest live weight, carcass weight, lean meat percentage, drip loss, glycolysis potential, muscle diameter, and relative mRNA expression levels of type IIb muscle fibers as well as the lowest ultimate pH (p < 0.05). The lightness value of DBS was the highest (p < 0.05). Among the three crossbred pigs, myristic, arachidic, palmitoleic, and eicosenoic acids were the highest in BDS. These results indicated that the carcass traits of local crossbred pigs were worse than those of DLY pigs, but meat quality was markedly higher, with BDS showing the best meat quality.

Low-protein diets supplemented with isoleucine alleviate lipid deposition in broilers through activating 5' adenosine monophosphate-activated protein kinase and janus kinase 2/signal transducer and activator of transcription 3 signaling pathways

This study aimed to evaluate the effect of isoleucine (Ile) on growth performance, meat quality and lipid metabolism of broilers fed a low-protein diet (LPD). The 396 one-day-old male Cobb broilers were allocated to 4 treatment groups as follows: control diet (CON), LPD, LPD + 0.13% Ile (LPD-LI) and LPD + 0.26% Ile (LPD-HI), with nine replicates of 11 broilers each for 42 d. The Ile increased average daily gain, average daily feed intake, fiber density and the mRNA level of myosin heavy chain (MyHC)-I in breast muscle, and decreased feed to gain ratio, shear force, fiber diameter and the mRNA level of MyHC-IIb in breast muscle, which were impaired by the LPD. Compared to the LPD group, broilers in LPD-LI and LPD-HI groups had lower serum lipid levels, liver fat content, abdominal adipose percentage and mRNA levels of peroxisome proliferator-activated receptor-γ, CCAAT/enhancer binding protein-α, ki-67, topoisomerase II alpha (TOP2A) and thioredoxin-dependent peroxidase 2 in abdominal adipose and liver X receptors-α, sterol regulatory element binding protein 1 (SREBP1), acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) in liver, and higher mRNA levels of peroxisome proliferator activated receptor-α, carnitine palmitoyl-transferase 1 (CPT-1), and acyl-CoA oxidase 1 (ACOX1) in liver, which were equal to the CON levels. A LPD supplemented with Ile decreased enzyme activities of ACC and FAS in liver and glycerol-3-phosphate dehydrogenase and TOP2A in abdominal adipose, and increased enzyme activities of CPT-1 and ACOX1 in liver. Furthermore, Ile supplementation enhanced the mRNA level of leptin receptor and protein levels of phospho-5' adenosine monophosphate-activated protein kinase (AMPK), mechanistic target of rapamycin, ribosomal protein 70 S6 kinase, janus kinase 2 (JAK2), and signal transducer and activator of transcription 3 (STAT3), and decreased the protein level of SREBP1 in the liver of broilers in LPD group. In conclusion, dietary supplementation with Ile to 0.83% could improve growth performance and meat quality and alleviate lipid deposition of broilers fed a LPD through activating AMPK and JAK2/STAT3 signaling pathways.

Hyperpigmentation Inhibits Early Skeletal Muscle Development in Tengchong Snow Chicken Breed

Tengchong snow, which has white feathers and black meat, is one of the most important black-bone chicken breeds and a genetic treasure of black food in China. Although the black meat traits are dominant, there are some chickens with white meat traits born in the process of folk selection and breeding. The purpose of this study was to compare the differences in skeletal muscle development between Tengchong snow black meat chickens (BS) and white meat chickens (WS), as well as whether excessive melanin deposition has an effect on skeletal muscle development. The BS and WS groups were selected to determine their muscle development difference at stages of 1, 7, 14, 21, and 42 days, using histological stain methods to analyze the development and composing type of breast and leg muscle fibers, as well as the count of melanin in BS muscle fibers. Finally, we were validated key candidate genes associated with muscle development and melanin synthesis. The results showed that BS breast muscle development was inhibited at 7, 14, and 21 days, while the leg muscle was inhibited at 7, 14, 21, and 42 days, compared to WS. Melanin deposition was present in a temporal migration pattern and was greater in the leg muscles than in the breast muscles, and it focused around blood vessels, as well as the epithelium, perimysium, endomysium, and connective tissue. Additionally, melanin produced an inhibitory effect similar to MSTN during skeletal muscle fiber development, and the inhibition was strongest at the stage of melanin entry between muscle fibers, but the precise mechanisms need to be confirmed. This study revealed that melanin has an inhibitory effect on the early development of skeletal muscle, which will provide new insights into the role of melanin in the black-boned chicken and theoretical references for the future conservation and utilization of black-boned chicken.

Sox6 Differentially Regulates Inherited Myogenic Abilities and Muscle Fiber Types of Satellite Cells Derived from Fast- and Slow-Type Muscles

Adult skeletal muscle is primarily divided into fast and slow-type muscles, which have distinct capacities for regeneration, metabolism and contractibility. Satellite cells plays an important role in adult skeletal muscle. However, the underlying mechanisms of satellite cell myogenesis are poorly understood. We previously found that Sox6 was highly expressed in adult fast-type muscle. Therefore, we aimed to validate the satellite cell myogenesis from different muscle fiber types and investigate the regulation of Sox6 on satellite cell myogenesis. First, we isolated satellite cells from fast- and slow-type muscles individually. We found that satellite cells derived from different muscle fiber types generated myotubes similar to their origin types. Further, we observed that cells derived from fast muscles had a higher efficiency to proliferate but lower potential to self-renew compared to the cells derived from slow muscles. Then we demonstrated that Sox6 facilitated the development of satellite cells-derived myotubes toward their inherent muscle fiber types. We revealed that higher expression of Nfix during the differentiation of fast-type muscle-derived myogenic cells inhibited the transcription of slow-type isoforms (MyH7B, Tnnc1) by binding to Sox6. On the other hand, Sox6 activated Mef2C to promote the slow fiber formation in slow-type muscle-derived myogenic cells with Nfix low expression, showing a different effect of Sox6 on the regulation of satellite cell development. Our findings demonstrated that satellite cells, the myogenic progenitor cells, tend to develop towards the fiber type similar to where they originated. The expression of Sox6 and Nfix partially explain the developmental differences of myogenic cells derived from fast- and slow-type muscles.

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.

Untargeted Metabolomics Reveals the Effect of Selective Breeding on the Quality of Chicken Meat

The selection for improved body weight is an effective approach in animal breeding. Guangxi Partridge chickens have differentiated into two lines under selective breeding, which include line S and line D that have shown statistically significant differences in body weight. However, the meat quality analysis in our study indicated that the quality of breast and thigh muscles in line S chickens changed, which included increased values of L*, b*, and drip loss and decreased a* value, pH, and shear force in skeletal muscles. To illuminate the effect of selection on skeletal muscles, LC-MS/MS metabolomics was performed to explore differentiated metabolites in divergent tissues from the two chicken lines. The results of principal component analysis and orthogonal projection to latent structures discriminant analysis suggested that metabolites of different groups were separated, which suggested that selective breeding certainly affected metabolism of skeletal muscles. KEGG analysis identified that valine, leucine, and isoleucine biosynthesis, glycerophospholipid metabolism, and glutathione metabolism noteworthily changed in breast muscle. Amino sugars and nucleotide sugar metabolism, ascorbate and aldarate metabolism, the pentose phosphate pathway, pentose and glucuronate interconversions, fructose and mannose metabolism, and glycerophospholipid metabolism were remarkedly identified in thigh muscle. These screened pathways suggested oxidative stress in breast and thigh muscles, which corresponded with our previous results. Therefore, this study determined that glycerophospholipid metabolism conservatively functioned in muscle flavor and development but exhibited different anti-oxidative patterns in different skeletal muscles. Overall, the present study identified several differentiated metabolites and pathways for exploring differences in meat quality between different broiler populations.