Woody Breast Myopathy Research Articles

Effects of the Marek's Disease Vaccine on the Performance, Meat Yield, and Incidence of Woody Breast Myopathy in Ross 708 Broilers When Administered Alone or in Conjunction with In ovo and Dietary Supplemental 25-Hydroxycholecalciferol.

The effects of the Marek's disease vaccine (MDV) on the live performance, breast meat yield, and incidence of woody breast myopathy (WBM) of Ross 708 broilers were investigated when administered alone or in conjunction with in ovo and dietary supplemental 25-hydroxycholecalciferol (25OHD3). At 18 d of incubation (doi), four in ovo injection treatments were randomly assigned to live embryonated Ross 708 broiler hatching eggs: (1) non-injected; (2) commercial MDV alone; or MDV containing either (3) 1.2 or (4) 2.4 μg of 25OHD3. An Inovoject multi-egg injector was used to inject a 50 μL solution volume into each egg. The birds were provided a commercial diet that contained 250 IU of cholecalciferol/kg of feed (control) or a commercial diet that was supplemented with an additional 2760 IU of 25OHD3/kg of feed (HyD-diet). In the growout period, 14 male broilers were placed in each of 48 floor pens resulting 6 replicated pens per in ovo x dietary treatment combination. Live performance variable were measured at each dietary phases from 0 to 14, 15 to 28, and 29 to 40 d of age (doa). At 14 and 40 doa, pectoralis major (P. major) and pectoralis minor (P. minor) muscles were determined for one bird within each of the six replicate pens. At 41 doa, WBM incidence was determined. No significant main or interaction effects occurred for WBM among the dietary or in ovo injection treatments. However, in response to in ovo 25OHD3 supplementation, BW and BWG in the 29 to 40 doa period and BWG and FCR in the 0 to 40 doa period improved. In addition, at 40 and 41 doa, breast meat yield increased in response to in ovo and dietary 25OHD3 supplementation. Future research is needed to determine the possible reasons that may have been involved in the aforementioned improvements.

Reduced ribonucleotide reductase RRM2 subunit expression increases DNA damage and mitochondria dysfunction in woody breast chickens.

The aim of this study was to investigate the roles of ribonucleotide reductase subunit M2 (RRM2; subunit of ribonucleotide reductase) in severe woody breast (WB) and normal breast muscles. 40 8-week-old male Ross-708 broiler chickens. Quantitative PCR was performed to determine gene expression, and commercial ELISA/assay kits were used to obtain several enzymatic activities. Results showed that RRM2 activity (P = .0002) and RRM2 (P = .05) and hydroxymethylbilane synthase expression (impaired oxygen transport and metabolism, P = .002) were reduced in WB, while caveolin-3 (defected membrane integrity, P = .09), endoglin (increased fibrosis, P = .06), and secreted protein acidic rich in cysteine (metabolic dysregulation, P = .09) expression tended to increase in WB. WB tended to have increased levels of homocysteine (P = .06), aspartate aminotransferase mitochondria (P = .02), pyruvate kinase (P = .04), DNA damage (P = .06), creatine kinase (P = .05), and triglyceride (P = .002) but decreased ATPase activity (P = .01), all indicating mitochondria dysfunction and tissue damage. In this study, differences in various enzyme activities and increased DNA damage suggest that RRM2-mediated mitochondrial abnormalities may play a role in WB myopathy.

Changes in gene expression in the intestinal mucus of broilers with woody breast myopathy

Previous work has shown that dietary treatments affect woody breast (WB) incidence differently, which indicates that gut conditions such as gut barrier function, inflammation, and oxidative stress are likely related to WB. In this study, dietary supplementation with antibiotics (bacitracin) or probiotics (Bacillus subtilis) was investigated for their effects on the expression of transcripts related to gut barrier function, inflammation, and oxidative stress in the mucus lining of the jejunum from broilers with or without WB. A split-plot experimental design was used in this study. The dietary treatments served as the main plot factor and the breast muscle condition was the subplot factor. On d 41, jejunum mucus was collected from 1 bird from each of 3 replicate pens in each 3 dietary treatment groups that exhibited WB and an additional bird that contained a normal breast (3 biological replicates/treatment/phenotype; 3 × 3 × 2, total N = 18). Total RNA was extracted using a commercial RNA extraction kit. The expression levels of CLDN1, MUC6, TLR2A, TLR2B, TLR4, IFN-γ, IL-1β, IL-8L1, IL-10, NOS2, and SOD were determined using 2-step RT-qPCR analysis. The gene expression difference in ΔCt values was determined after normalizing with the chicken 18S rRNA gene. When the significant differences occurred between treatments, the relative fold change was calculated using the ΔΔCt method and the significance level was calculated. The PROC GLM procedure of SAS 9.4 was used, and the level of significance was set at P ≤ 0.05. There were no significant interactive effects between diet and the breast muscle condition on the expression of any of the genes tested. However, birds with WB exhibited higher MUC6 (P < 0.0001) gene expression levels than birds with normal breast muscles. In addition, the expression of SOD decreased in birds that were fed the antibiotic diet when compared to birds that were fed the probiotic diet (P = 0.014). In conclusion, WB identified in broilers tested in the current study is attributed to increased expression of mucin, indicating a correlation between WB incidence and gel-forming mucin secretion and pathogen signaling.

Potential Role of Ribonucleotide Reductase Enzyme in Mitochondria Function and Woody Breast Condition in Broiler Chickens.

The cellular events leading to the development of the woody breast myopathy in broiler breast muscle are unclear. Affected woody breast muscle exhibits muscle fiber degeneration/regeneration, connective tissue accumulation, and adverse morphological changes in mitochondria. Ribonucleotide reductase (RNR) is an enzyme for the synthesis of dNTP, which is important for mitochondria DNA content (mtDNA). RNR consists of two subunits: RRM1/RRM2. A decrease in RRM2 is associated with a decrease in mtDNA and mitochondria proteins, leading to impaired ATP production. The objective of this study was to investigate potential RNR differences between woody breast (WB) and normal (N) breast muscle by examining RRM2 expression and associated pathways. Gene expression and enzyme activities were examined by qPCR and commercial kits. Results showed that RRM2 expression reduced for WB (p = 0.01) and genes related to mitochondria, including ATP6 (p = 0.03), COX1 (p = 0.001), CYTB (p = 0.07), ND2 (p = 0.001) and ND4L (p = 0.03). Furthermore, NDUFB7 and COX 14, which are related to mitochondria and ATP synthesis, tended to be reduced in WB. Compared to N, GLUT1 reduced for WB (p = 0.05), which is responsible for glucose transport in cells. Consequently, PDK4 (p = 0.0001) and PPARG (p = 0.008) increased in WB, suggesting increased fatty acid oxidation. Citric synthase activity and the NAD/NADH ratio (p = 0.02) both reduced for WB, while WB increased CHRND expression (p = 0.001), which is a possible indicator of high reactive oxygen species levels. In conclusion, a reduction in RRM2 impaired mitochondria function, potentially ATP synthesis in WB, by increasing fibrosis and the down-regulation of several genes related to mitochondria function.

White striping, woody breast and spaghetti meat: Cooccurrence and relationship with breast fillet weight in big broiler chicken flocks

The present study aimed to determine the incidence and coincidence of white striping (WS), woody breast (WB) and spaghetti meat (SM) in raw chicken breast meat (n = 300) collected 3–3.5 h post mortem from commercial broiler flocks (Ross 708 males, 56 days of age). The fillets were scored for the occurrence and severity of WS, WB and SM using visual and tactile methods, and the relationship between myopathies and breast weight was evaluated. A total of 88% of samples (out of 300) had either one or a combination of three myopathies, leaving only 12% without any myopathies. Approximately 29% of the fillets had only one myopathy present, with 59% of the samples demonstrating the cooccurrence of breast myopathies. In the present study, 47.7% of WB samples also exhibited WS, while the cooccurrence of WB and SM was exhibited in 14.7%. Based on binomial logistic regression, an increase in WB scores decreases the odds that the fillet may be affected by SM myopathy. No association was found between SM and fillet weight. Multinomial logistic regression showed that the weight of breast fillets was positively associated with WB1 (P = 0.011), WB2 (P < 0.001), and WB3 (P < 0.001). Furthermore, positive associations were found between WS1 and WB3 (P = 0.004) as well as between WS2 and WB3 (P < 0.001). The percentage distribution changes of each WB and WS myopathy score were used in relation to the 10 weight groups. The percentages of WB3 increased and WB0 decreased as the average fillet weight increased. Regarding linear regression, these results exhibited a positive linear relationship for both WB (R2 = 0.91, P < 0.001) and WS (R2Â =Â 0.71, P = 0.002) myopathy with fillet weight. A high prevalence of myopathies was observed. The incidence of severe WB categories and the overall high cooccurrence rate are alarming.

Potential role of endoplasmic reticulum stress in broiler woody breast myopathy.

Although broiler (meat-type) chickens are one of the most efficient protein sources that supports the livelihoods and food security of billions of people worldwide, they are facing several challenges. Due to its unknown etiology and heavy economic impact, woody breast (WB) myopathy is one of the most challenging problems facing the poultry industry, and for which there is no effective solution. Here, using a primary chicken myotube culture model, we show that hypoxia and endoplasmic reticulum (ER) stress are an integral component of the etiology of the myopathy. Multiple components of the ER stress response are significantly upregulated in WB as compared with normal muscle, and this response was mimicked by hypoxic conditions in chicken primary myotube culture. In addition, apoptotic pathways were activated as indicated by increases in active caspase 3 protein levels in both WB-affected tissues and hypoxic myotube culture, and caspase 3 activity and apoptosis in hypoxic myotube culture. Finally, as a phenotypic hallmark of WB is enhanced fibrosis and increased collagen aggregation, here, we show that hypoxic conditions increase collagen 1A1 and 1A2 gene expression, as well as collagen 1 protein levels in primary myotubes. These effects were partially reversed by tauroursodeoxycholic acid (TUDCA), an ER-stress inhibitor, in myotube culture. Taken together, these findings indicate that hypoxia and ER stress are present in WB, hypoxia can upregulate the cell death arm of the unfolded protein response (UPR) and lead to collagen production in a culture model of WB. This opens new vistas for potential mechanistic targets for future effective interventions to mitigate this myopathy.

Classification and Feature Extraction Using Supervised and Unsupervised Machine Learning Approach for Broiler Woody Breast Myopathy Detection

Bioelectrical impedance analysis (BIA) was established to quantify diverse cellular characteristics. This technique has been widely used in various species, such as fish, poultry, and humans for compositional analysis. This technology was limited to offline quality assurance/detection of woody breast (WB); however, inline technology that can be retrofitted on the conveyor belt would be more helpful to processors. Freshly deboned (n = 80) chicken breast fillets were collected from a local processor and analyzed by hand-palpation for different WB severity levels. Data collected from both BIA setups were subjected to supervised and unsupervised learning algorithms. The modified BIA showed better detection ability for regular fillets than the probe BIA setup. In the plate BIA setup, fillets were 80.00% for normal, 66.67% for moderate (data for mild and moderate merged), and 85.00% for severe WB. However, hand-held BIA showed 77.78, 85.71, and 88.89% for normal, moderate, and severe WB, respectively. Plate BIA setup is more effective in detecting WB myopathies and could be installed without slowing the processing line. Breast fillet detection on the processing line can be significantly improved using a modified automated plate BIA.

Internal organ and skeletal muscle development in commercial broilers with woody breast myopathy

Increasing growth rate, body weight, and breast muscle yield have been linked to broiler muscle problems such as woody breast (WB). The aim of this study was to investigate the internal organ and skeletal muscle development of broilers with WB myopathy under dietary and Eimeria challenge treatments. A 3 diet (control, antibiotic, or probiotic) × 2 challenge (control or Eimeria) × 2 sex factorial arrangement of treatments was used in a randomized complete block design. Ross × Ross 708 chicks were randomly assigned to 96 floor pens with 12 treatment combinations (8 replicates per treatment). Internal organs were sampled on d 13 and 41. Skeletal muscles were sampled on d 41. Internal organ and skeletal muscle weights were analyzed using a 3-way analysis of variance (ANOVA). Relationships between WB and internal organ and skeletal muscle weights were analyzed using one-way ANOVA as all treatments were pooled together and regrouped according to WB scores. On d 41, absolute and relative heart weights were greater in males when they were averaged over diet and challenge treatments (P < 0.001 and P = 0.026, respectively). The birds with WB score 3 had greater absolute heart (P = 0.0002) and spleen weights (P = 0.016), but there was no difference in relative spleen weight (P > 0.05). When averaged over diet and challenge treatments, males have greater absolute duodenum, jejunum, and ileum weights (for all P < 0.0001). Compared with birds with normal breasts, the birds with WB scores 1, 2, and 3 had a greater live weight (for all P < 0.0001) and absolute and relative breast weights (for all P < 0.0001). The birds with WB score 1, 2, and 3 had greater (P < 0.0001) absolute but lower (P < 0.0001) relative drumstick, thigh, and wing weights. Results indicated that broilers with WB had lower relative proventriculus and gizzard weights and greater relative breast meat weight with lower relative drumstick, thigh, and wing muscle weights.

Effects of dietary bacitracin or Bacillus subtilis on the woody breast myopathy-associated gut microbiome of Eimeria spp. challenged and unchallenged broilers

Study suggested that dysbiosis of the gut microbiota may affect the etiology of woody breast (WB). In the current study, the cecal microbiota and WB in chickens fed three different diets were investigated. A total of 504 male chicks were used in a randomized complete block design with a 3 (Diet) × 2 (Challenge) factorial arrangement of treatments with 6 replicates per treatment, 6 treatments per block, and 14 birds per treatment. The experimental diets were a control diet (corn-soybean meal basal diet), an antibiotic diet (basal diet + 6.075 mg bacitracin/kg feed), and a probiotic diet (basal diet + 2.2 × 108 CFU Bacillus subtilis PB6/kg feed). On d 14, birds that were assigned to the challenge treatment received a 20 × live cocci vaccine. On d 41, breast muscle hardness in live birds was palpated and grouped into normal (NB) and WB phenotypes. Cecal contents were collected and their bacterial compositions were analyzed and compared. The genomic DNA of the cecal contents was extracted and the V3 and V4 regions of 16S rRNA gene were amplified and sequenced via an Illumina MiSeq platform. There were no differences (P > 0.05) in Shannon and Chao 1 indexes between the challenges, diets, and phenotypes (NB vs. WB). However, there was a difference (P = 0.001) in the beta diversity of the samples between the challenged and nonchallenged groups. Relative bacterial abundance differed (false discovery rate, FDR < 0.05) between the challenge treatments, but there were no significant differences (FDR > 0.05) among the three diets or two phenotypes. Predicted energy metabolism, nucleotide metabolism, and amino acid and coenzyme biosynthesis activities only differed (q-value < 0.05) between challenged and nonchallenged groups. The cocci challenge altered the gut microbial composition on Butyricicoccus pullicaecorum, Sporobacter termitidis, and Subdoligranulum variabile, but the dietary antibiotic and probiotic treatments did not impact gut microbial composition. No strong association was found between WB myopathy and gut microbial composition in this study.

An Investigation of the Altered Textural Property in Woody Breast Myopathy Using an Integrative Omics Approach.

Woody breast (WB) is a myopathy observed in broiler Pectoralis major (PM) characterized by its tough and rubbery texture with greater level of calcium content. The objective of this study was to investigate the functionality/integrity of WB sarcoplasmic reticulum (SR), which may contribute to the elevated calcium content observed in WB and other factors that may influence WB texture. Fourteen Ross line broiler PM [7 severe WB and 7 normal (N)] were selected, packaged, and frozen at −20°C at 8 h postmortem from a commercial processing plant. Samples were used to measure pH, sarcomere length, proteolysis, calpain activity, collagenase activity, collagen content, collagen crosslinks density, and connective tissue peak transitional temperature. Exudate was also collected from each sample to evaluate free calcium concentration. The SR fraction of the samples was separated and utilized for proteomic and lipidomic analysis. The WB PM had a higher pH, shorter sarcomeres, lower % of intact troponin-T, more autolyzed μ/m calpain, more activated collagenase, greater collagen content, greater mature collagen crosslinks density, and higher connective tissue peak transitional temperature than the N PM (p ≤ 0.05). Exudate from WB PM had higher levels of free calcium than those from N PM (p < 0.05). Proteomics data revealed an upregulation of calcium transport proteins and a downregulation of proteins responsible for calcium release (p < 0.05) in WB SR. Interestingly, there was an upregulation of phospholipase A2 (PLA2), and cholinesterase exhibited a 7.6-fold increase in WB SR (p < 0.01). Lipidomics data revealed WB SR had less relative % of phosphatidylcholine (PC) and more lysophosphatidylcholine (LPC; p < 0.05). The results indicated that upregulation of calcium transport proteins and downregulation of calcium-release proteins in WB SR may be the muscle’s attempt to regulate this proposed excessive signaling of calcium release due to multiple factors, such as upregulation of PLA2 resulting in PC hydrolysis and presence of cholinesterase inhibitors in the system prolonging action potential. In addition, the textural abnormality of WB may be the combined effects of shorter sarcomere length and more collagen with greater crosslink density being deposited in the broiler PM.

Effects of the in ovo injection of vitamin D3 and 25-hydroxyvitamin D3 in Ross 708 broilers subsequently fed commercial or calcium and phosphorus-restricted diets. I. Performance, carcass characteristics, and incidence of woody breast myopathy1,2,3

Effects of the in ovo-injection of vitamin D3 (D3) and 25-hydroxyvitamin D3 (25OHD3) on broiler performance, carcass characteristics, and woody breast myopathy (WBM) incidence were investigated. Live embryonated Ross 708 broiler hatching eggs (2,880) were randomly assigned to one of the following in ovo injection treatments: (1) diluent (50 μL); diluent (50 μL) containing either (2) 2.4 μg D3; (3) 2.4 μg 25OHD3; or (4) 2.4 μg D3 + 2.4 μg 25OHD3. Eggs were injected at 18 d of incubation (doi) using an Inovoject multiegg injector. At hatch, 18 male chicks were randomly placed in each of 6 replicate pens belonging to each in ovo injection and, dietary treatment combination. Birds were fed either a commercial diet or a diet restricted in calcium and phosphorous (ReCaP) content by 20% for the starter, grower and finisher dietary phases. Broiler performance was determined in each dietary phase and breast muscle yield was also determined at 14 and 40 d of age (doa). At 41 and 46 doa, birds were processed for determination of WBM, carcass weight, and the absolute and relative (% of carcass weight) weights of various carcass parts. Compared to birds fed the commercial diet, birds fed ReCaP diets experienced a reduction in performance from 14 to 40 doa, in breast meat yield at 41 and 46 doa, and in WBM at 41 and 46 doa. At 14 and 40 doa, breast meat yield in birds that received an in ovo injection of 25OHD3 alone was higher compared to birds that received diluent alone or a combination of D3 and 25OHD3. Lower WBM incidence in ReCaP-fed birds was associated with a lower breast weight. An increase in breast meat yield in response to 25OHD3 alone may be due to improved immunity and small intestine morphology. However, further study is needed to determine the aforementioned effects.

Influence of Woody Breast Myopathy on Sarcomere Length and Tensile Strength in Commercial Broiler Pectoralis major Muscle

Woody breast syndrome is characterized by degenerative changes at the muscle fiber level and accumulation of connective tissue between the fibers. This study explored effects of the syndrome on muscle properties by focusing on a comparison of the sarcomere lengths between normal and woody breast muscles, including cranial and middle parts, surface and deeper layers, electrically stimulated and nonstimulated muscles, and their combinations. Tensile strengths longitudinally and transversally to the muscle fiber direction in the cranial and middle parts of the muscles were determined. The overall sarcomere lengths of woody breasts were longer than normal muscles (1.93 μ m vs. 1.88 μm; P &amp;lt; 0.05). The surface layer had overall longer sarcomere lengths than the deeper layer (cranial surface vs. cranial deeper layer: 1.97 vs. 1.89 μ m; middle surface vs. middle deeper layer: 1.93 vs.1.84 μ m; P &amp;lt; 0.05). Compared with normal breast muscles, woody breast muscles had longer sarcomeres in the surface layer; however, sarcomere length did not differ in the deeper layer. Electrically stimulated chicken breasts generally had longer sarcomere lengths (2.00 vs. 1.82 μm; P &amp;lt; 0.001). There was no significant difference in tensile strength between normal and focal woody breast (mild local lesion, usually in the cranial end) samples when fiber direction or sample location was studied (P &amp;gt; 0.05), but there was a clear difference between normal and focal versus diffuse (severe woody breast lesion throughout the muscle) samples (P &amp;lt; 0.001). Tensile strength was much greater in diffuse woody breast muscles when extended longitudinally or transversely to the fiber direction. In conclusion, although this study did not show sarcomere lengths in living muscle, it suggests an imbalance in sarcomere lengths in different parts of the breast muscle, which may induce a reduction in the functionality and strength of the muscle.

Hypoxia further exacerbates woody breast myopathy in broilers via alteration of satellite cell fate

Woody breast (WB) condition has created a variety of challenges for the global poultry industry. To date, there are no effective treatments or preventative measures due to its unknown (undefined) etiology. Several potential mechanisms including oxidative stress, fiber-type switching, cellular damage, and altered intracellular calcium levels have been proposed to play a key role in the progression of the WB myopathy. In a previous study, we have shown that WB is associated with hypoxia-like status and dysregulated oxygen homeostasis. As satellite cells (SC) play a pivotal role in muscle fiber repair and remodeling under stress conditions, we undertook the present study to determine satellite cell fate in WB-affected birds when reared in either normoxic or hypoxic conditions. Modern random bred broilers from 2015 (n = 200) were wing banded and reared under standard brooding practices for the first 2 wk post-hatch. At 15 d, chicks were divided in 2 body weight-matched groups and reared to 6 wk in either control local altitude or hypobaric chambers with simulated altitude of 6,000 ft. Birds were provided ad libitum access to water and feed, according to the Cobb recommendations. At 6 wk of age, birds were processed and scored for WB, and breast samples were collected from WB-affected and unaffected birds for molecular analyses (n = 10/group). SCs were isolated from normal breast muscle, cultured in vitro, and exposed to normoxia or hypoxia for 2 h. The expression of target genes was determined by qPCR using 2−∆∆Ct method. Protein distribution and expression were determined by immunofluorescence staining and immunoblot, respectively. Data were analyzed by the Student's t test with significance set at P < 0.05. Multiple satellite cell markers, myogenic factor (Myf)-5 and paired box (PAX)-7 were significantly decreased at the mRNA and protein levels in the breast muscle from WB-affected birds compared to their unaffected counterparts. Lipogenic-and adipogenic-associated factors (acetyl-CoA carboxylase, ACCα; fatty acid synthase, FASN, malic enzyme, ME; and ATP citrate lyase, ACLY) were activated in WB-affected birds. These data were supported by an in vitro study where hypoxia decreased the expression of Myf5 and Pax7, and increased that of ACCα, FASN, ME, and ACLY. Together, these data indicate that under hypoxic condition, SC change fate by switching from a myogenic to an adipogenic program, which explains at least partly, the etiology of the WB myopathy.

Cecal microbiota contribute to the development of woody breast myopathy

The objective of this study was to characterize the bacterial diversity of cecal microbiota in broilers related to breast phenotype, diet, and genetic strain. Broilers from 2 genetic strains (120 birds/strain) were fed a control diet (15 birds/pen) and an amino acid reduced diet (15 birds/pen, digestible lysine, total sulfur amino acids, and threonine reduced by 20% compared to the control diet). At 8 wk of age, 4 male broilers with normal breast (NB, 1 chick per pen) and 4 male broilers with woody breast (WB, 1 chick per pen) were selected for each treatment (strain × diet). The DNA of cecal samples was extracted and the 16S rRNA genes were sequenced and analyzed. There were no differences (P > 0.05) in the alpha diversity of gut microbiota between 2 phenotypes (NB vs. WB), 2 strains, or 2 diets (control vs. reduced). However, principal coordinate analysis plots (beta diversity) revealed that there were composition differences in samples between the 2 phenotypes (P = 0.001) and the 2 diets (P = 0.024). The most abundant phyla in all samples were Firmicutes, followed by Bacteroidetes and Proteobacteria. There were differences (false discovery rate, FDR < 0.05) in bacterial relative abundance between phenotypes and between diet treatments, but not (FDR > 0.05) between the 2 genetic strains. Selenomonas bovis (12.6%) and Bacteroides plebeius (12.3%) were the top 2 predominant bacteria in the ceca of WB birds; however, the relative abundances of these 2 bacteria were only 5.1% and 1.2% in NB birds, respectively. Function analysis predicted that the metabolic activities differed (q < 0.05) only between phenotypes. The microbiota of WB birds was characterized as reduced glycolysis and urea cycle but increased tricarboxylic acid (TCA) cycles, sugar degradation, and purine and pyrimidine nucleotides biosynthesis. Further studies are needed to investigate if WB incidence could be reduced by regulating gut microbiota and the potential mechanism that leads to decreased WB incidence.

Evaluation of multi blade shear (MBS) for determining texture of raw and cooked broiler breast fillets with the woody breast myopathy

The objective of this study was to evaluate a novel multi-blade Shear (MBS) method for measuring texture properties of both raw and cooked broiler fillets (pectoralis major) with the woody breast (WB) myopathy. A total of 180 broiler breast fillets (60 normal [NOR], 60 moderate WB [MOD], and 60 severe WB [SEV]) in two meat states (fresh never-frozen, n = 144; frozen/thawed, n = 36) were chosen based on their WB scores. In each trial, half of the fillets were used for measuring raw meat texture and the other half for cooked meat texture measurement. Blunt Meullenet-Owens Razor Sear (BMORS) was used for comparison. In fresh raw broiler fillets, both the MBS and BMORS methods detected differences between NOR, MOD, and SEV fillets (P < 0.001). In cooked broiler fillets, the methods were equivalent in their ability to separate SEV from NOR fillets. The MBS measurements showed greater Spearman correlation coefficients with the WB scores (rs ≥ 0.70 in raw and ≥ 0.33 in cooked) compared to the BMORS measurements (rs = 0.63 in raw and ≤ 0.27 in cooked) for both fresh and cooked breast fillets. In addition, the MBS measurements were either as precise as or more precise than BMORS measurements regardless of meat condition (fresh vs. cooked) and the shear parameter. These results suggest that the MBS method is more reliable in measuring tactile characteristics of broiler breast fillets with the WB myopathy compared with the BMORS method.

Woody breast myopathy broiler show age-dependent adaptive differential gene expression in Pectoralis major and altered in-vivo triglyceride kinetics in adipogenic tissues

A study was conducted to understand the differentially expressed genes in Pectoralis (P) major under woody breast (WB) myopathy condition in a high yielding broiler strain using RNA-sequencing at the growing (d 21) and finishing (d 42 and d 56) grow-out ages. Follow-up study was conducted to understand the in vivo triglyceride (TG) synthesis (d 49) occurring in adipogenic tissues using deuterium oxide (2H2O) as a metabolic tracer. Results indicated the top physiological systems affected in myopathy broiler were related to the musculo-skeletal system (d 21, 42, and 56) and cardiovascular system (d 42 and 56). Ubiquitin-specific proteases are expressed higher in myopathy broiler at d 21 (OTUD1) and d 42 (SACS) that potentially indicated higher degradation of muscle protein occurring at those ages. While genes related to transcription factors and muscle cell differentiation (ZNF234, BTG2) and muscle growth (IGF1) were upregulated with myopathy broiler suggesting concurrent muscle fiber regeneration. The downregulation of PYGB and MGAM genes related to carbohydrate transport and metabolism at d 42 potentially indicated nutrient-deficient state of myopathy affected fibers; whereas the nutrient-deficient physiological state of cells seemed to be counteracted by up-regulation of genes related to carbohydrate (ALDOB, GPD1L2) at d 56. There was a reduced (P < 0.05) in vivo TG synthesis in liver of the myopathy broiler (0.123 %/hr) compared to non-myopathy broiler (0.197 %/hr). The majority of TG synthesized in liver with myopathy broiler could conceivably be delivered to P. major (rather than to abdominal fat pad storage) to fulfil the increased energy need of muscle cells (via TG lipolysis and fatty acid [FA] oxidation). The increased utilization of FAs in the WB affected muscle could result in reduced secretion of FAs into blood circulation leading to sub-optimal availability of FAs for re-esterification for TG synthesis in liver. Results indicated that myopathy broiler at later age (d 56) of grow-out period were synchronously going through adaptive physiological processes of feedback responses to adverse cellular states.

Effects of broiler genetic strain and dietary amino acid reduction on meat yield and quality (part II)

Genetic selection and advances in nutrition have improved broiler growth performance. However, meat quality issues have gained preference over increased growth rate. These meat quality issues may be reduced by lowering dietary amino acid (AA) content. In the present study, 5 common commercial broiler strains were fed either a control or an AA-reduced diet. The control diet was formulated to contain the highest digestible AA (lysine, total sulfur AA, and threonine) levels recommended for the 5 strains. The AA-reduced diet was formulated to contain 20% lower levels of these 3 digestible AA than in the control diet. This resulted in a 5 (strains) × 2 (AA levels) factorial arrangement. A total of 1,280 straight run broilers were randomly allocated to 8 replicate blocks. The AA reduction decreased absolute breast weights of 3 strains on day 42 and 2 strains on day 56, and decreased absolute weights of tender, wing, drumstick, and thigh on both day 42 and 56 for all 5 strains. However, the absolute fat pad weight and relative fat pad and thigh weights to BW were increased in the AA reduction treatments on both day 42 and 56. The AA reduction contributed to the lower breast meat pH on both day 42 and 56, which may have been directly related to decreased severe woody breast myopathy (WBM) incidence on day 42 and moderate WBM incidence on day 56. The severity of WBM was positively related to breast weight in all 10 treatments on both day 42 and 56, with the exception of birds in strain 3 on day 56 that were fed the AA-reduced diet. At the same time, AA reduction was more cost-effective when WBM incidence was considered in a theoretical model. In conclusion, WBM severity was associated with higher breast weight in birds of most strains fed either a control or AA-reduced diet. Dietary AA reduction decreased processing yields but decreased WBM incidence, which may be more economical.

Broiler genetics influences proteome profiles of normal and woody breast muscle

Wooden or woody breast (WB) is a myopathy of the pectoralis major in fast-growing broilers that influences the quality of breast meat and causes an economic loss in the poultry industry. The objective of this study was to evaluate growth and proteome differences between 5 genetic strains of broilers that yield WB and normal breast (NB) meat. Eight-week-old broilers were evaluated for the WB myopathy and divided into NB and WB groups. Differential expression of proteins was analyzed using 2-dimensional gel electrophoresis and LC-MS/MS to elucidate the mechanism behind the breast myopathy because of the genetic backgrounds of the birds. The percentages of birds with WB were 61.3, 68.8, 46.9, 45.2, and 87.5% for strains 1-5, respectively, indicating variability in WB myopathy among broiler strains. Birds from strains 1, 3, and 5 in the WB group were heavier than those in the NB group (P < 0.05). Woody breast meat from all strains were heavier than NB meat (P < 0.05). Within WB, strain 5 had a greater breast yield than strains 1, 3, and 4 (P < 0.0001). Woody breast from strains 2, 3, 4, and 5 had a greater breast yield than NB (P < 0.05). Six proteins were more abundant in NB of strain 5 than those of strains 2, 3, and 4, and these proteins were related to muscle growth, regeneration, contraction, apoptosis, and oxidative stress. Within WB, 14 proteins were differentially expressed between strain 5 and other strains, suggesting high protein synthesis, weak structural integrity, intense contraction, and oxidative stress in strain 5 birds. The differences between WB from strain 3 and strains 1, 2, and 4 were mainly glycolytic. In conclusion, protein profiles of broiler breast differed because of both broiler genetics and the presence of WB myopathy.

Using air deformation of raw fillet surfaces to identify severity of woody breast myopathy in broiler fillets

This study was conducted to determine the effectiveness of air deformation on fillet surfaces to assess hardness and identify woody breast (WB) in raw fillets of broilers. Fillets (n = 120) were categorized in normal (NORM), mild (MILD) and severe (SEV) WB. All fillets were subjected to compression force (CF) analysis and pressurized air (344 kPa) was directed at the ventral surface of each fillet in the cranial region and the deformation area was measured. Fillets were cooked and sheared using Muellenet Owens Razor Shear (MORS) and blunt version of MORS (BMORS). CF increased as severity of WB increased (P < 0.05). Diameter of deformation area decreased (P < 0.05) as WB severity increased. CF was correlated to air deformation (rs = -0.43 to -0.66, P < 0.05). BMORS force and energy was higher (P < 0.05) in SEV fillets compared to those in MILD and NORM. SEV fillets had higher (P < 0.05) peak counts (PC) of shear curves using MORS or BMORS than MILD and NORM fillets (P < 0.05). The results indicate that WB can be identified by CF and that the use of air deformation in raw fillets which may be potentially utilized as a tool for WB assessment. Using BMORS paired with the peak counting method may be a better texture analysis method to access WB condition.

Texture and quality of chicken sausage formulated with woody breast meat

Woody breast (WB) myopathy is a quality defect, afflicting a large portion of commercial broilers to some degree. The WB myopathy is commonly attributed to rapid bird growth and characterized by excessive fibrosis within the pectoralis major, which is thought to cause the palpably hardened texture observed in the afflicted breast meat. These phenotypically tough breast fillets are not marketed for traditional intact muscle products owing to poor quality and eating experience. Potential avenues for these afflicted breast fillets include their use in formulation of fresh and cooked sausages. Two degrees of WB fillets (moderate and severe) were used as a replacement for normal (unafflicted) breast fillet meat at levels of 25, 50, and 100%, in a sausage formulation with 1.5% salt and 15% chicken fat. All 6 treatments were compared with a control formulation (100% normal breast meat) and analyzed for texture profile, cook loss, color, and proximate composition. Moisture and fat content for all formulations were similar (P = 0.95 and P = 0.33, respectively), but with increase in the inclusion rate of WB meat, lower protein content (P < 0.01) was observed. Raw sausage color indicated a lighter (P < 0.05) color for the control sausage (100% normal) than with both 100% moderate and 100% severe formulations. Similarly, sausages containing 100% severe WB meat were the darkest (L∗; P < 0.05), but they were similar to sausages containing 100% moderate (P > 0.05) WB meat. Texture profile analysis indicated a decrease in hardness, cohesiveness, and springiness with use of 100% severe WB meat, while inclusion of lower proportions of severe WB meat resulted in similar textural characteristics. These results indicate the possibility of using WB fillet meat in a sausage formulation with minimal impact on sausage texture profiles.