MeRIP sequencing reveals the regulation of N6-methyladenosine in muscle development between hypertrophic and leaner broilers.

Meat production performance is the most important economic trait in broilers, and skeletal muscle, as the largest organ in animals, is directly related to meat production during embryonic and postnatal growth and development. N6-Methyladenosine (m6A) is a chemical modification occurs on RNA adenosine that has been reported to participate in a variety of biological processes in all species. However, there are still few reports on the regulatory role of muscle growth and development in poultry after birth. This study aims to reveal the distribution of m6A modification sites in chicken pectoralis major muscle after birth and find out the regulatory relationship between m6A and muscle development. As representatives of leaner (Xinghua chicken [XH]) and hypertrophic (White Recessive Rock chicken [WRR]) broilers, there are significant differences in body weight, muscle fiber diameter, and muscle fiber cross-sectional area between XH and WRR chickens. RNA sequencing detected a total of 397 differentially expressed genes (DEG) in the pectoralis major muscle of XH and WRR chicken, and these DEGs were mainly enriched in catalytic activity and metabolic pathways. MeRIP sequencing results showed that among all 6,476 differentially modified m6A peaks, about 90% peaks (5,823) were differentially down regulated in XH chickens. The joint analysis of the mRNA and MeRIP sequencing data found 145 DEGs with differential m6A peak, ALKBH5 as a m6A demethylase, was also included. The highly expression of ALKBH5 in the muscle tissue of poultry and differential expression between XH and WRR chickens suggest that ALKBH5 may play a crucial role in regulating muscle development. Our results revealed that there were significant differences in growth rate, body weight, muscle fiber diameter, and fiber cross-section area between WRR and XH chicken, as well as significant differences in m6A methylation level and muscle metabolism level.

Animal protein-soybean oil-based broiler diet optimizes net profit at the expense of desirable ω-6 fatty acids from the breast muscle of the broiler chicken.

Total 288 Ross-308-day-old male broiler chicks were randomly distributed into six dietary treatment groups in a two-way ANOVA with 2 × 3 factorial arrangements (two factors, i.e., dietary protein and energy having two types of protein, e.g., plant, animal and three different sources of energy, e.g., soybean oil, rice bran oil and sunflower oil) to justify if animal protein-soybean oil based broiler diet optimizes net profit at the expense of desirable ω-6 fatty acids in the breast muscle of the broiler chicken. Average daily feed intake (ADFI), final live weight (FLW), average daily gain (ADG), feed efficiency (FE), carcass characteristics, cardio-pulmonary morphometry, fatty acid profile of the breast muscle and cost-benefit analysis were measured. Results indicated that animal protein significantly increased 4.27% FLW, 6.13% ADFI, 4.31% ADG and 2.93% wing weight. Accordingly, soybean oil increased 4.76% FLW, 3.80% ADG and 1.36% dressing percentage at the expense of 12.07% proventriculus weight compared with sunflower oil. The generalized linear model identified no interaction effects of the sources of protein and energy on overall performance of the birds. Replacement of vegetable protein by animal protein decreased 14.01% ∑ω-3, 12.16% ∑ω-6 and 12.21% sum of polyunsaturated fatty acids (∑PUFA) and concomitantly increased 10.82% sum of saturated fatty acids (∑SFAs) in the breast muscle (Pectoralis major). Accordingly, replacement of sunflower oil by soybean oil decreased 29.17% ∑ω-3, 6.71% ∑ω-6, 11.62% sum of monounsaturated fatty acids (∑MUFAs) and 7.33% ∑PUFAs and concurrently increased 18.36% ∑SFAs in the breast muscle of the broiler birds. It was concluded that animal protein-soybean oil-based broiler diet optimized net profit at the expense of desirable ω-3 and ω-6 fatty acids in the breast muscle of the broiler chicken.

The Effects of In Ovo Feeding of Selenized Glucose on Selenium Concentration and Antioxidant Capacity of Breast Muscle in Neonatal Broilers.

This study aims to investigate the impacts of in ovo feeding (IOF) of selenized glucose (SeGlu) on selenium (Se) level and antioxidant capacity of breast muscle in newborn broilers. After candling on 16 day of incubation, a total of 450 eggs were randomly divided into three treatments. On the 17.5th day of incubation, eggs in a control treatment were injected with 0.1 mL of physiological saline (0.75%), while the 2nd group and 3rd group were supplied with 0.1 mL of physiological saline containing 10 µg Se from SeGlu (SeGlu10 group) and 20 µg Se from SeGlu (SeGlu20 group). The results showed that in ovo injection in both SeGlu10 and SeGlu20 increased the Se level and reduced glutathione concentration (GSH) in pectoral muscle of hatchlings (P < 0.05). Compared with the control group, the SeGlu20-treated chicks significantly enhanced the activity of the superoxide dismutase (SOD) and mRNA expression of NAD(P)H quinone dehydrogenase 1 (NQO1) in breast muscle, while there was upregulation in mRNA expressions of glutathione peroxidase 1 (GPX-1) and thioredoxin reductase 1 (TrxR1) and higher total antioxidant capacity (T-AOC) in SeGlu10 treatment (P < 0.05). However, no significant difference on enzyme activities of glutathione peroxidase (GR), glutathione reductase, thioredoxin reductase, concentration of malondialdehyde, and free radical scavenging ability (FRSA) of superoxide radical (O2-•) and hydroxyl radical (OH•) was observed among the three treatments (P > 0.05). Therefore, IOF of SeGlu enhanced Se deposition in breast muscle of neonatal broilers. In addition, in ovo injection of SeGlu could increase the antioxidant capacity of newborn chicks possibly through upregulating the mRNA expression of GPX1, TrxR1, and NQO1, as well as the SOD activity.

Effects of high-dose folic acid on protein metabolism in breast muscle and performance of broilers.

Attaining the optimal feed conversion ratio is the unaltered goal for poultry breeding, meat yield is one of the vital reference indexes for that. Folic acid is involved in protein metabolism by acting as a transmitter of one carbon unit, and the detail mechanism for the high-dose folic acid on growth of broiler skeletal muscle is still unclarified. The present study was conducted to investigate the effect and regulatory mechanism of folic acid on deposition and metabolism of protein in broiler breast muscle. A total of 196 one-day-old AA broilers were randomly assigned to 2 treatment groups. The chicks were fed corn-soybean diet with folic acid levels of 1.3 mg/kg (CON) or 13 mg/kg (FA), respectively. The results showed that high dose of folic acid significantly increased the body weight gain, average daily gain, average daily feed intake, and feed conversion ratio of broilers during 1 to 42 d. Compared with control group, folic acid statistically augmented the breast muscle ratio of broilers at 42 d, abdominal fat percentage was also decreased in FA group. Folic acid significantly increased the gene expression of folate receptor (FR) in duodenum and jejunum at 21 d, and its relative expression in jejunum of broilers at 42 d. Furthermore, relative expression of myogenin in broiler breast muscle was upregulated in folic acid group. Folic acid supplementation significantly enhanced the protein expression of phosphorylated serine/threonine kinase (AKT) and ribosomal protein S6 kinase 1 (S6K1) in the breast muscle of broilers at 21 d and 42 d. In conclusion, the results proved that high-dose folic acid activated the AKT/mammalian target of rapamycin (mTOR) pathway and increased the activity of phosphorylation of S6K1, thereby regulating the protein deposition in breast muscle. Meanwhile, the gene expression of the myogenic determinant factor was upregulated by folic acid and then promoted the growth of breast muscle. Consequently, the growth performance, meat production and feeding efficiency were improved of broilers by adding folic acid at 13 mg/kg.

Pectoralis major muscle atrophy is associated with mitochondrial energy wasting in cachectic patients with gastrointestinal cancer.

BACKGROUND: Cancer cachexia is a multifactorial syndrome characterized by involuntary and pathological weight loss, mainly due to skeletal muscle wasting, resulting in a decrease in patients' quality of life, response to cancer treatments, and survival. Our objective was to investigate skeletal muscle alterations in cachectic cancer patients. METHODS: This is a prospective study of patients managed for pancreatic or colorectal cancer with an indication for systemic chemotherapy (METERMUCADIG - NCT02573974). One lumbar CT image was used to determine body composition. Patients were divided into three groups [8 noncachectic (NC), 18 with mild cachexia (MC), and 19 with severe cachexia (SC)] based on the severity of weight loss and muscle mass. For each patient, a pectoralis major muscle biopsy was collected at the time of implantable chamber placement. We used high-resolution oxygraphy to measure mitochondrial muscle oxygen consumption on permeabilized muscle fibres. We also performed optical and electron microscopy analyses, as well as gene and protein expression analyses. RESULTS: Forty-five patients were included. Patients were 67% male, aged 67 years (interquartile range, 59-77). Twenty-three (51%) and 22 (49%) patients were managed for pancreatic and colorectal cancer, respectively. Our results show a positive correlation between median myofibres area and skeletal muscle index (P = 0.0007). Cancer cachexia was associated with a decrease in MAFbx protein expression (P < 0.01), a marker of proteolysis through the ubiquitin-proteasome pathway. Mitochondrial oxygen consumption related to energy wasting was significantly increased (SC vs. NC, P = 0.028) and mitochondrial area tended to increase (SC vs. MC, P = 0.056) in SC patients. On the contrary, mitochondria content and networks remain unaltered in cachectic cancer patients. Finally, our results show no dysfunction in lipid storage and endoplasmic reticulum homeostasis. CONCLUSIONS: This clinical protocol brings unique data that provide new insight to mechanisms underlying muscle wasting in cancer cachexia. We report for the first time an increase in mitochondrial energy wasting in the skeletal muscle of severe cachectic cancer patients. Additional clinical studies are essential to further the exploring and understanding of these alterations.

Dietary guanidineacetic acid supplementation ameliorated meat quality and regulated muscle metabolism of broilers subjected to pre-slaughter transport stress by metabolomics analysis.

Pre-slaughter transport stress could induce multiple comprehensive variations in physiological and metabolic parameters of broilers. However, the entire metabolomics of pre-slaughter transport stress and supplementation of exogenous energy regulatory substances on broilers is still poorly understood. The metabolome characteristics of broilers subjected to 3 h pre-slaughter transport stress combined with 1,200 mg/kg guanidinoacetic acid (GAA1,200) supplementation were analyzed using gas chromatography-mass spectrometry (GC-MS) in this study. The results showed that, compared to the control group (no transport), 3 h pre-slaughter transport stress (T3h) decreased creatine (Cr), phosphocreatine (PCr) and adenosine triphosphate (ATP), and increased adenosine diphosphate (ADP), adenosine monophosphate (AMP) and the ratio of AMP to ATP in pectoralis muscle (PM) of broilers by high performance liquid chromatography (HPLC) analysis. However, GAA1,200 supplementation reversed the negative effects induced by 3 h pre-slaughter transport stress. Besides, GAA1,200 supplementation elevated mRNA expression of creatine transporter in PM. Our metabolomics approaches demonstrated that 38 and 48 significant metabolites were separately identified between the control group and T3h group, and T3h group and 3 h pre-slaughter transport stress combined with GAA1,200 supplementation group using the standard of variable importance in the projection values >1 and P < 0.05. Among these, the metabolites involved in amino acid metabolism (alanine, glycine, serine, threonine, cysteine , methionine, phenylalanine, tyrosine, and tryptophan), oxidative stress (3-methylhistidine, 1-methylhistidine and glutathione), non-protein amino acid (citrulline) metabolism, and energy metabolism (Cr, PCr, sarcosine, and glycocyamine) were confirmed through pathway enrichment analysis, which could be chosen as suitable candidate targets for further analysis of the effects of exogenous energy substances on broilers subjected to transport stress.

Oxidative stress induced by hydrogen peroxide promotes glycolysis by activating CaMKK/LKB1/AMPK pathway in broiler breast muscle.

Oxidative stress is common in the whole process of broiler production, and breast muscle is one of the target organs most vulnerable to oxidative attack. When broilers are subjected to oxidative stress, the regulation of adenosine 5-monophosphate activated protein kinase (AMPK) is a critical path to maintain the dynamic balance of intracellular energy. However, whether calcium/calmodulin-dependent protein kinase (CaMKK) and liver kinase B1 (LKB1) are involved in the regulation of AMPK activation in broiler breast muscle under oxidative stress has not been elucidated. In this study, a total of 144 one-day-old male Ross 308 chicks were selected, with an average body weight of 43.44 ± 0.04 g. The broilers were divided into 3 groups with 6 replicates of 8 broilers each (control group, intraperitoneal injection of physiological saline group, and intraperitoneal injection of hydrogen peroxide [H2O2] group), the injection time was selected on the 16th and 37th day of the experimental period, the injection volumes were 1.0 mL/kg broiler body weight. The results of this experiment showed that H2O2 exposure reduced the average daily gain (ADG) and increased the feed to gain ratio (F/G), the level of corticosterone (CORT) and the activity of lactate dehydrogenase (LDH) in serum were increased after H2O2 exposure. H2O2 exposure also increased the contents of reactive oxygen species (ROS) and protein carbonyl, but decreased the activities of catalase (CAT), total antioxidant capacity (T-AOC), total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-Px) in breast muscle. After H2O2 exposure, the activity of pyruvate dehydrogenase (PDH) was decreased, the content of glycogen was reduced, and the contents of adenosine monophosphate (AMP) and lactate were increased in breast muscle. In addition, H2O2 exposure increased the content of Ca2+, upregulated the protein expression levels of CaMKK1 and p-AMPK, and increased the activities of hexokinase (HK) and LDH in breast muscle. These findings suggested that the activation of CaMKK/LKB1/AMPK signaling pathway would be associated with the accelerated glycolysis of broiler breast muscle under oxidative stress.

Coping with extremes: High-altitude sparrows enhance metabolic and thermogenic capacities in the pectoralis muscle and suppress in the liver relative to their lowland counterparts.

Animals living at high altitudes are challenged by the extreme environmental conditions of cold temperature and hypobaric hypoxia. It is not well understood how high-altitude birds enhance the capacity of metabolic thermogenesis and allocate metabolic capacity in different organs to maximize survival in extreme conditions of a cold winter. The Qinghai-Tibet Plateau (QTP) is the largest and highest plateau globally, offering a natural laboratory for investigating coping mechanisms of organisms inhabiting extreme environments. To understand the adaptive strategies in the morphology and physiology of small songbirds on the QTP, we compared plasma triiodothyronine (T3), pectoralis muscle mitochondrial cytochrome c oxidase (COX) and state IV capacities, the expression of peroxisome proliferator-activated receptor γ coactivator α (PGC-1α), adenine nucleotide translocase (ANT), uncoupling protein (UCP), and adenosine monophosphate-dependent kinase (AMPK) α1 mRNA in the pectoralis and liver of Eurasian tree sparrows (Passer montanus) from high-altitude (3,230 m), medium-altitude (1400 m), and low-altitude (80 m) regions. Our results showed that high-altitude sparrows had greater body masses, longer wings and tarsometatarsi, but comparable bill lengths relative to medium- and low-altitude individuals. High-altitude sparrows had higher plasma T3 levels and pectoralis muscle mitochondrial COX capacities than their lowland counterparts. They also upregulated the pectoralis muscle mRNA expression of UCP, PGC-1α, and ANT proteins relative to low-altitude sparrows. Unlike pectoralis, high-altitude sparrows significantly down-regulated hepatic AMPKα1 and ANT protein expression as compared with their lowland counterparts. Our results contribute to understanding the morphological, biochemical, and molecular adaptations in free-living birds to cope with the cold seasons in the extreme environment of the QTP.

Prospect of early vascular tone and satellite cell modulations on white striping muscle myopathy.

Polyphasic myodegeneration potentially causes severe physiological and metabolic disorders in the breast muscle of fast-growing broiler chickens. To date, the etiology of recent muscle myopathies, such as the white striping (WS) phenotype, is still unknown. White striping-affected breast meats compromise the water holding capacity and predispose muscle to poor vascular tone, leading to the deterioration of meat qualities. Herein, this review article provides insight on the complexities around chicken breast myopathies: (i) the etiologies of WS occurrence in chicken; (ii) the metabolic changes that occur in WS defect in pectoralis major; and (iii) the interactions between breast muscle physiology and vascular tone. It also addressed the effects of nutritional supplements on muscle myopathies on chicken breast meats. Moreover, the review explored breast muscle biology focusing on the early preparation of satellite and vascular cells in fast-growth chicken breeds. Transcriptomics and histological analyses revealed poor vascularity in breast muscle of fast growth chickens. Thus, we suggest in ovo feeding of nutrients promoting vascularization and satellite cells replenishment as a potential strategy to enhance endothelium-derived nitric oxide availability to promote vascularization in the pectoralis major muscle region.

Effect of growth selection of broilers on breast muscle satellite cell function: Response of satellite cells to NOV, COMP, MYBP-C1, and CSRP3.

The wooden breast (WB) myopathy is characterized by the palpation of a hard pectoralis major muscle that results in the necrosis and fibrosis of muscle fibers in fast-growing heavy weight meat-type broiler chickens. Necrosis of existing muscle fibers requires the repair and replacement of these myofibers. Satellite cells are responsible for the repair and regeneration of myofibers. To address how WB affects satellite cell function, top differentially expressed genes in unaffected and WB-affected pectoralis major muscle determined by RNA-Sequencing were studied by knocking down their expression by small interfering RNA in proliferating and differentiating commercial Ross 708 and Randombred (RBch) satellite cells. RBch satellite cells are from commercial 1995 broilers before WB appeared in broilers. Genes studied were: Nephroblastoma Overexpressed (NOV); Myosin Binding Protein-C (MYBP-C1); Cysteine-Rich Protein 3 (CSRP3); and Cartilage Oligomeric Matrix Protein (COMP). Ross 708 satellite cells had greatly reduced proliferation and differentiation compared to RBch satellite cells. MYBP-C1, CSRP3, and COMP reduced late proliferation and NOV did not affect proliferation in both lines. The timing of the knockdown differentially affected differentiation. If the expression was reduced at the beginning of proliferation, the effect on differentiation was greater than if the knockdown was at the beginning of differentiation. These data suggest, appropriate gene expression levels during proliferation greatly impact multinucleated myotube formation during differentiation. The effect of slow myofiber genes MYBP-C1 and CSRP3 on proliferation and differentiation suggests the presence of aerobic Type I satellite cells in the pectoralis major muscle which contains anaerobic Type IIb cells.

Hydrogen peroxide-induced oxidative stress impairs redox status and damages aerobic metabolism of breast muscle in broilers.

Oxidative stress has always been a hot topic in poultry science. However, studies concerning the effects of redox status and glucose metabolism induced by hydrogen peroxide (H2O2) in the breast muscle of broilers have been rarely reported. This study was aimed to evaluate the impact of intraperitoneal injection of H2O2 on oxidative damage and glycolysis metabolism of breast muscle in broilers. We also explored the activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway to provide possible mechanism of the redox imbalance. Briefly, a total of 320 one-day-old Arbor Acres chicks were randomly divided into 5 treatments with 8 replicates of 8 birds each (noninjected control, 0.75% saline-injected, 2.5, 5.0, and 10.0% H2O2-injected treatments). Saline group was intraperitoneally injected with physiological saline (0.75%) and H2O2 groups received an intraperitoneal injection of H2O2. The dosage of the injection was 1.0 mL/kg BW. All birds in the saline and H2O2 groups were injected on days 16 and 37 of the experimental period. At 42 d of age, 40 birds (8 cages per group and one chicken per cage) were selected to be stunned electrically (50 V, alternating current, 400 Hz for 5 s each one), and then immediately slaughtered via exsanguination. The results showed that broilers in the H2O2 injection group linearly exhibited higher contents of reactive oxygen species, carbonyl and malondialdehyde, and lower total antioxidant capacity and glutathione peroxidase activities. With the content of H2O2 increased, the H2O2 groups linearly downregulated the mRNA expressions of GPX, CAT, HMOX1, NQO1, and Nrf2 and its downstream target genes. In addition, H2O2 increased serum activities of creatine kinase and lactate dehydrogenase. Meanwhile, in the pectoral muscle, the glycogen content was linearly decreased, and the lactate content was linearly increased in muscle of broilers injected with H2O2. In addition, the activities of glycolytic enzymes including pyruvate kinase, hexokinase, and lactate dehydrogenase were linearly increased after exposure to H2O2. In conclusion, H2O2 injection could impair antioxidant status and enhance anaerobic metabolism of breast muscle in broilers.

Morinda officinalis polysaccharides improve meat quality by reducing oxidative damage in chickens suffering from tibial dyschondroplasia.

Tibial dyschondroplasia (TD) is the common leg disease in commercial broilers. However, the effects of TD on meat quality and the protective of Morinda officinalis polysaccharide (MOP) are largely unknown. Three hundred broiler chicks (one-day-old) were equally allocated into control (CON), TD and MOP-treated groups for 15 days. The results indicated that TD influenced morphology and meat quality-related parameters of the breast muscle, and changed the activity and mRNA expression of antioxidant enzymes in plasma and breast muscles. Moreover, metabolomics profiling of breast muscle revealed that the main altered metabolites 4-guanidinobutyric acid and chenodeoxycholic acid, which are related to meat quality and oxidative stress. Additionally, 500 mg/L MOP effectively restored the content of meat metabolites and oxidative damage. These findings suggest that oxidative damage caused by TD may affect meat quality in broilers by changing the content of breast muscle metabolites and that MOP supplementation has a restorative effect.

Selenium Mitigates Cadmium-Induced Adverse Effects on Trace Elements and Amino Acids Profiles in Chicken Pectoral Muscles.

Cadmium (Cd), as one of the most toxic heavy metals, has become a widespread environmental contaminant and threats the food quality and safety. The protective effect of selenium (Se) on Cd-induced tissue lesion and cytotoxicity in chicken has been extensively reported. The objective of this study was to investigate the antagonistic effect of Se on Cd-induced damage of chicken pectoral muscles via analyzing the trace elements and amino acids profiles. Firstly, 19 trace elements contents were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that under Cd exposure, the contents of Cd, lead (Pb), mercury (Hg), aluminum (Al), and lithium (Li) were significantly elevated, and the contents of Se, iron (Fe), and chromium (Cr) were significantly reduced. However, supplementing Se significantly reversed the effects induced by Cd. Secondly, the amino acids contents were detected by L-8900 automatic amino acid analyzer. The results showed that supplementing Se increased significantly Cd-induced decrease of valine (Val), leucine (Leu), arginine (Arg), and proline (Pro). Thirdly, the results of principal component analysis (PCA) showed that cobalt (Co), manganese (Mn), silicium (Si), and Pro may play special roles in response to the process of Se antagonizes Cd-induced damage of pectoral muscles in chickens. In summary, these results indicated that different trace elements and amino acids possessed and exhibited distinct responses to suffer from Se and/or Cd in chicken pectoral muscles. Notably, Se alleviated Cd-induced adverse effects by regulating trace elements and amino acids profiles in chicken pectoral muscles.

Population Pharmacokinetics of Danofloxacin After Single Intramuscular Dose Administration in California Brown Pelicans (Pelecanus occidentalis californicus).

The pharmacokinetics of danofloxacin was investigated in rehabilitated California brown pelicans (Pelecanus occidentalis californicus) after a single intramuscular injection at a dose of 15 mg/kg body weight. The concentration of the drug in plasma was assayed by high-pressure liquid chromatography. A sparse-sampling design was used to reduce the number of samples (1-4 venipunctures) obtained from 24 brown pelicans. A population pharmacokinetic analysis with nonlinear mixed-effects modeling was used to accommodate the sparse-sampling strategy. The nonlinear mixed-effects modeling approach measured both fixed effects (typical values for the population) and random effects (between-subject variability) for this population. A 1-compartment model best represented the concentration-versus-time data after injection. After injection, the elimination half-life, peak concentration, area under the curve, and volume of distribution were 2.76 hours, 2.5 µg/mL, 13.75 µg/h/mL, and 4.35 L/kg, respectively. Rate of absorption was highly variable among the birds. The intramuscular injection of danofloxacin in pelicans at this dose produced plasma concentrations that meet therapeutic targets for bacteria with a minimum inhibitory concentration of ≤0.25 µg/mL. This dose can be used for future studies to evaluate the efficacy of danofloxacin for treating susceptible bacteria.

Increased Expression of Lipid Metabolism Genes in Early Stages of Wooden Breast Links Myopathy of Broilers to Metabolic Syndrome in Humans.

Wooden breast is a muscle disorder affecting modern commercial broiler chickens that causes a palpably firm pectoralis major muscle and severe reduction in meat quality. Most studies have focused on advanced stages of wooden breast apparent at market age, resulting in limited insights into the etiology and early pathogenesis of the myopathy. Therefore, the objective of this study was to identify early molecular signals in the wooden breast transcriptional cascade by performing gene expression analysis on the pectoralis major muscle of two-week-old birds that may later exhibit the wooden breast phenotype by market age at 7 weeks. Biopsy samples of the left pectoralis major muscle were collected from 101 birds at 14 days of age. Birds were subsequently raised to 7 weeks of age to allow sample selection based on the wooden breast phenotype at market age. RNA-sequencing was performed on 5 unaffected and 8 affected female chicken samples, selected based on wooden breast scores (0 to 4) assigned at necropsy where affected birds had scores of 2 or 3 (mildly or moderately affected) while unaffected birds had scores of 0 (no apparent gross lesions). Differential expression analysis identified 60 genes found to be significant at an FDR-adjusted p-value of 0.05. Of these, 26 were previously demonstrated to exhibit altered expression or genetic polymorphisms related to glucose tolerance or diabetes mellitus in mammals. Additionally, 9 genes have functions directly related to lipid metabolism and 11 genes are associated with adiposity traits such as intramuscular fat and body mass index. This study suggests that wooden breast disease is first and foremost a metabolic disorder characterized primarily by ectopic lipid accumulation in the pectoralis major.

Amyloid A amyloidosis secondary to avian tuberculosis in naturally infected domestic pekin ducks (Anas platyrhynchos domestica).

To investigate the correlation between avian tuberculosis and duck amyloidosis, the liver, lung, spleen, kidney, duodenum and pectoralis muscle of ducks naturally infected with Mycobacterium avium subsp. avium were used to detect amyloidosis by Congo red staining and potassium permanganate-Congo red staining. The expression level of IL-1ß, IL-6, IL-10, TNF-α and SAA2 were detected by quantitative real-time RT-PCR (qRT-PCR). The results showed that the liver, lung, spleen, kidney, duodenum and pectoralis muscle of the infected ducks exhibited amyloid proteins under ordinary light microscopy and the polarization light under polarized light microscopy. However, no amyloid deposition in potassium permanganate-Congo red staining sections indicated that the amyloidosis was AA amyloidosis. In addition, the expression level of IL-1ß, IL-6, IL-10, TNF-α and SAA2 increased from 4 to 43. This study showed that avian tuberculosis could induce secondary amyloidosis in naturally infected ducks.

Attenuating effects of guanidinoacetic acid on preslaughter transport-induced muscle energy expenditure and rapid glycolysis of broilers.

This study evaluated the effects of dietary guanidinoacetic acid (GAA) supplementation on growth performance, plasma variables, muscle energy status, glycolytic potential, and meat quality of broilers experiencing transport stress during the summer. A total of 320 28-day-old male Arbor Acres broilers were randomly allotted to 3 dietary treatments, including a GAA-free basal control diet (160 birds) and basal diet supplementation with 600 (80 birds) or 1,200 mg/kg (80 birds) GAA for 14 D. On the morning of day 42, after an 8-h fast, the birds fed basal diets were divided into 2 equal groups, and all birds in the 4 groups of 80 birds were transported according to the following protocols: 1) a 0.5-h transport of birds on basal diets (as a lower-stress control group), 2) a 3-h transport of birds on basal diets, and a 3-h transport of birds on basal diets supplemented with either 3) 600 or 4) 1,200 mg/kg GAA. The results revealed that dietary supplementation with GAA at 600 and 1,200 mg/kg for 14 D prior to slaughter did not affect growth performance, carcass traits, and most textural characteristics and chemical composition of the pectoralis major (PM) muscle (P > 0.05). In the GAA-free group, a 3-h transport increased the broiler live weight loss, elevated the plasma corticosterone concentration, decreased the plasma glucose concentration, muscle concentrations of ATP, creatine and energy charge value, increased the muscle AMP concentration and AMP/ATP ratio, and accelerated glycolysis metabolism, which resulted in inferior meat quality (lower pH and higher drip loss, P < 0.05). However, dietary addition of GAA at 1,200 mg/kg increased the mRNA expression of S-adenosyl-l-methionine: N-guanidino-acetate methyltransferase in the liver and creatine transporter in both the liver and PM muscle. It also elevated muscle concentrations of creatine and phosphocreatine (P < 0.05), which helps improve meat quality by ameliorating the 3-h transport-induced muscle energy expenditure and delaying anaerobic glycolysis of broilers.

Effects of intra-yolk-sac injection of dextrose and albumin on performance, jejunum morphology, liver and pectoral muscle glycogen and some serum metabolites of broilers.

This study carried out to investigate the effects of intra-yolk-sac injection (IYSI) of some solutions including 1 ml of distilled water, dextrose 20% and albumin 20% on hatch percentage, performance traits, jejunum morphology, glycogen content of liver and breast and serum metabolites in broilers (Ross 308). Fertile eggs were injected into the yolk sac at day 8 of incubation period. Results showed that hatchability, absolute body weight (BW), feed intake (FI) and feed conversion ratio (FCR) at day 7 and 14 of growing period were not different among treatments, but in comparison with control group, BW and FCR were numerally better by IYSI of albumin. In addition, IYSI of albumin increased jejunum villus height at hatch day, but crypt depth was not affected by any injection treatments. Also, the glycogen concentrations of liver and pectoral muscle in albumin injected group were significantly higher than control at hatch and 7th day respectively. At hatch day, serum glucose and cholesterol concentrations were, respectively, maximum and minimum statistically by IYSI of albumin which continued numerally up to 7th day of rearing period. Furthermore, liver glycogen and serum glucose concentrations were directly correlated on the day of hatch. In conclusion, the IYSI of albumin could increase performance traits, jejunum villus height, liver and breast glycogen and serum glucose in broiler chicks.

The effect of sexual maturity and egg production on skeletal muscle (pectoralis major and gastrocnemius) protein turnover in broiler breeder pure lines.

A study was conducted to evaluate the effect of sexual maturity on pectoralis major and gastrocnemius muscle protein turnover in broiler breeder pure lines. Protein turnover in skeletal muscle tissue was determined in 4 broiler breeder pure lines (Line A, Line B, Line C and Line D) at 22, 27, 33, 37, 44, and 50 wk of age. A completely randomized design with a factorial arrangement 4 × 6 (4 lines and 6 time periods (ages)) was used. There were 5 replicates per line/time and each hen represented a replicate. Five hens/line at each age were given an intravenous flooding-dose of 15N-phenylalanine (150 mM, 40 atom percent excess (APE) at a dose of 10 mL/kg. After 10 min, birds were euthanized using CO2 asphyxiation and the breast and leg muscle excised and snap frozen in liquid nitrogen for protein turnover analysis. Excreta was collected from each breeder for 3-methyl histidine (3-MH) analysis. There was a significant age effect for the breast muscle fractional synthesis rate (FSR), but no main effects (age and line) for leg muscle FSR. The FSR in breast muscle tissue decreased in hens from wk 22 (first egg) to wk 33 (peak egg production). There was a significant age effect on fractional breakdown rate (FBR) in breast and leg muscle. The FBR in breast muscle increased in hens from wk 22 to wk 33 and remained high through wk 37. Breast muscle FBR significantly decreased in hens from wk 37 to wk 50. The FBR in leg muscle tissue increased in hens from wk 33 to wk 37 and then decreased at wk 50. No line effect was seen for FSR or FBR. There is a large increase in skeletal muscle FBR during the transition for the pullet to sexual maturity with increases in skeletal muscle FBR in the breast and leg muscle through peak egg production. Protein turnover in skeletal muscle tissue is believed to be a source of nutrients for egg production.

Preslaughter Transport Effect on Broiler Meat Quality and Post-mortem Glycolysis Metabolism of Muscles with Different Fiber Types.

Preslaughter transport has been reported to decrease the quality of breast meat but not thigh meat of broilers. However, tissue-specific difference in glycogen metabolism between breast and thigh muscles of transported broilers has not been well studied. We thus investigated the differences in meat quality, adenosine phosphates, glycolysis, and bound key enzymes associated with glycolysis metabolism in skeletal muscles with different fiber types of preslaughter transported broilers during summer. Compared to a 0.5 h transport, a 3 h transport during summer decreased ATP content, increased AMP content and AMP/ATP ratio, and accelerated glycolysis metabolism via the upregulation of glycogen phosphorylase expression accompanied by increased activities of bound glycolytic enzymes (hexokinase, pyruvate kinase, and lactate dehydrogenase) in pectoralis major muscle, which subsequently increased the likelihood of pale, soft, and exudative-like breast meat. On the other hand, a 3 h transport induced only a moderate glycolysis metabolism in tibialis anterior muscle, which did not cause any noticeable changes in the quality traits of the thigh meat.