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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. [ABSTRACT FROM AUTHOR]

White striping (WS) is a common myopathy seen in fast-growing broilers. Studies have demonstrated that chitosan is effective as an antioxidant and has antiobesity and fat-absorption reduction properties. We hypothesized that the dietary supplementation of chitosan would have similar effects when fed to fast-growing broilers and would thus lower WS incidence and improve meat quality. One hundred twenty-six broilers were fed corn-soy diets. The grower and finisher diets contained either 0, 0.2, or 0.4% chitosan. After a 6 wk growth period, birds were euthanized, and then WS and gross pathology scores were assessed. Pectoralis major tissues were collected to evaluate cook loss, drip loss, histopathology scores, and the gene expression of CCR7, LECT2, CD36, PPARG, and PTGS2. There were no significant differences between the broiler weights, thus chitosan did not appear to compromise the overall growth of the broilers. Female broilers fed 0.4% chitosan had the lowest WS incidence, while male broiler fed 0.4% chitosan had the least cook loss. However, gene expression analyses did not offer insight into any grossly or histologically visualized differences in the muscles. Thus, while we can postulate that chitosan could have some positive effect in reducing WS incidence and improving meat quality, further studies are required to better scrutinize the mechanisms by which chitosan affects WS and other such myopathies in fast-growing broilers.

Background: There is a close relationship between breast muscle glucose metabolism, peripheral 5-hydroxytryptamine (5-HT), and myopathies in animals. Here, this study aimed to investigate the effects of different photoperiods on peripheral 5-HT metabolism, white striping (WS), and wooden breast (WB) in broilers. Methods: A total of 216 healthy 5-day-old (d) Arbor Acres (AA) male broilers were randomly assigned to 12L:12D, 18L:6D, and 24L:0D photoperiods for 4 weeks. Results: Compared with the 12L:12D photoperiod, we found the WB score in broilers was significantly increased in the 18L:6D and 24L:0D photoperiod at week 4 (p < 0.05). Muscle glycogen was significantly reduced (p < 0.05) and glycolysis was promoted in the breast muscles of broilers under the 18L:6D and 24L:0D photoperiods at week 2 and 4. Peripheral 5-HT concentrations, the mRNA expression of tryptophan hydroxylase 1 (TPH1) and serotonin transporter (SERT) in the cecal mucosa, and 5-hydroxytryptamine receptor 2A (5-HTR2A) mRNA expression in the breast muscle of broilers significantly up-regulated in the 18L:6D and 24L:0D photoperiod at week 2 and 4 (p < 0.05). Conclusions: Our findings revealed that extending the photoperiod improved the breast muscle growth rate, but up-regulated 5-HT synthesis and secretion to higher peripheral 5-HT, induced breast muscle glucose metabolism disorder, and increased WB incidence rates in broilers. [ABSTRACT FROM AUTHOR]

SUMMARY: This systematic review scrutinises the literature on white striping and wooden breast phenomena in broiler chickens, with a specific emphasis on identifying nutritional strategies designed to alleviate these myopathies. Additionally, the review sought to ascertain whether avian welfare was compromised when nutritional interventions were employed to address pectoral myopathies. Employing the ProKnow-C methodology, a total of twenty-two research articles were meticulously selected based on pre-established inclusion and exclusion criteria, following the Knowledge Development Process – Constructivist approach. Inclusion criteria encompassed studies featuring the application of nutritional strategies, specifically evaluating their impacts on the incidence of myopathies and their broader ramifications on animal welfare. Collated data facilitated to identify various nutritional strategies, evaluating their influence on the occurrence of pectoral myopathies, with researchers predominantly focusing on either white striping or wooden breast, or concurrently investigating both conditions. Upon a comprehensive analysis of the scientific content, the selected articles were categorised according to the applied nutritional strategies, namely: levels of crude protein, amino acids, and/or energy; antioxidants and various mineral sources; quantitative dietary restriction; and food additives. Our findings revealed a multitude of strategies deployed by the industry to mitigate the incidence of pectoral myopathies. Predominantly, these strategies fell into two broad categories: those associated with growth rate alterations, involving manipulation or retardation of the birds' growth curve throughout the production phase; and those utilising dietary antioxidants, whether natural or synthetic. Approaches related to the growth curve aimed at mitigating myopathy severity by controlling or slowing down avian growth. It is noteworthy that the scarcity of studies examining the impact of pectoral myopathies on animal welfare raises concerns that necessitate urgent attention from the scientific community. [ABSTRACT FROM AUTHOR]

The increase in the growth rate and the increase in the production of the pectoral muscle have been identified as the main causes for the appearance and increase of the presence of muscular alterations in chickens, as is the case of White striping and Wooden breast. Based on trials with mice, creatine (Cr) may have a protective role in some neuromuscular diseases and may reverse muscular dystrophy. Therefore, it is believed that guanidinoacetic acid (GAA), as a precursor of Cr, could play a role in preventing the inhibition of energy metabolism and lipid peroxidation related to muscle myopathies. Supplementation with GAA or Cr can restore the levels of Cr in the body, leading to a reduction in the use of Arg and Gly, improving the animal's zootechnical performance. Cr is an osmotically active substance, and increased intracellular levels can lead to the entry of water into the cell. This increased hydration induced by the increase in Cr in the body can increase protein synthesis and reduce proteolysis. Nucleotides and their metabolic products perform numerous functions in various metabolic processes of the organism: they serve as precursors of nucleic acids (DNA and RNA), they are components of coenzymes, physiological mediators and carriers of cellular energy. The maintenance of the cellular nucleotide pool occurs in two ways: synthesis of a new nucleotide or rescue or recycling pathway. However, research has indicated that these mechanisms may not provide amounts necessary for the maintenance of essential metabolic functions in some situations, such as rapid growth, recovery from injury and disease challenges, in addition to suggesting that nucleotides may help improve performance, prevention and reduction of the onset of myopathies. Therefore, the objective of this work is to present a review on the importance of food additives, their interaction with other nutrients and how they can influence the performance and occurrence of pectoral myopathies in broilers. [ABSTRACT FROM AUTHOR]

ABSTRACT: The study investigated guanidinoacetic acid (GAA) supplementation with varying dietary digestible arginine (Arg) and glycine+serine (Gly+Ser) concentrations in the starter phase, exploring respective carry-over effects on growth performance, blood chemistry, incidence of pectoral myopathies and proximate composition in broilers. A total of 2,800 one-day-old male broiler chicks were distributed in a central composite design with 2 factors and double experimental mesh, represented by supplementation or omission of 0.6 g per kg of GAA, with a central point represented by 107% of Arg and 147% of Gly+Ser, 4 factorial points (combinations of Arg/Gly+Ser concentrations: 96.4/132.5%; 117.6/132.5%; 96.4/161.5%, and 117.6/132.5%), and 4 axial points (combinations of axial points estimated for Arg and Gly+Ser, with the central points of 92/147%; 122/147%; 107/126.5, and 107/167.5%), totaling 18 treatments, 4 repetitions to factorial and axial points, 24 replicates to the central point, and 25 birds per pen. Feed conversion ratio (FCR) from d 1 to 10 had a linear response (P = 0.009) for the decreasing Arg content and a quadratic response (P = 0.047) for Gly+Ser concentrations. Broilers supplemented GAA had lower FCR compared with nonsupplemented groups from d 1 to 10 (P = 0.048) and d 1 to 42 (P = 0.026). Aspartate aminotransferase (AST) exhibited increasing and decreasing linear effects as a function of Arg (P = 0.008) and Gly+Ser (P = 0.020) concentrations, respectively. Guanidinoacetic acid decreased serum AST (P = 0.028). Guanidinoacetic acid reduced moderate + severe (P = 0.039) and mild (P = 0.015) Wooden Breast scores. The occurrence of normal White Striping increased (P = 0.002), while severe score was reduced (P = 0.029) with GAA supplementation. In conclusion, increased digestible Arg:Lys and 14% and 6% above the recommendations (107% and 147%), respectively, provided improved FCR during the starter phase. Dietary GAA supplementation (0.6 g per kg) improved FCR, reduced severity of breast myopathies and appears to have reduced muscle damage in broilers fed plant-based diets.

ABSTRACT: White striping (WS) that appears as white stripes parallel to the muscle fibrils is an emerging growth-related abnormality of broiler breast meat. The pathomechanism of this defect has not been fully understood despite intensive studies over the past decade. In the present study, endoplasmic reticulum (ER) stress and its associated apoptotic pathways were investigated to elucidate the potential role of these pathways in the development of WS. To this end, a total of 60 Pectoralis major (Pm) muscle samples were collected from 55-d-old Ross 308 male broiler chickens according to the severity of gross WS lesions (normal, mild, and severe). Histopathological and molecular analyses were conducted to evaluate the lesions and genes involved in the ER stress and related apoptosis. All the Pm samples, both with and without macroscopic WS lesions, showed varying degrees of myodegenerative lesions. Molecular analysis revealed that the transcript abundances of many components related to protein kinase R-like ER kinase (PERK) and inositol-requiring enzyme type 1 (IRE-1) signals of the ER stress response were significantly greater in severely WS-affected breast tissues compared to their mildly affected and normal counterparts. Similarly, the transcript abundances of apoptotic markers related to both signaling pathways were significantly greater in severe WS lesions than those of mildly affected and normal Pm tissues. Besides these, a significant increase in caspase-3 transcript abundance was seen in severe WS lesions in comparison with mild WS and normal breast muscles. Findings of this study suggest that ER stress response and its related apoptotic pathways are possibly activated in the breast muscle of broiler chickens with severe WS lesions. Based on these findings, it is speculated that ER stress-mediated apoptosis occupies a central role in the progression of WS in broiler chickens.

Abstract White striping (WS) is a myopathy of growing concern to the turkey industry. It is rising in prevalence and has negative consequences for consumer acceptance and the functional properties of turkey meat. The objective of this study was to conduct a genome-wide association study (GWAS) and functional analysis on WS severity. Phenotypic data consisted of white striping scored on turkey breast fillets (N = 8422) by trained observers on a 0–3 scale (none to severe). Of the phenotyped birds, 4667 genotypic records were available using a proprietary 65 K single nucleotide polymorphism (SNP) chip. The SNP effects were estimated using a linear mixed model with a 30-SNP sliding window approach used to express the percentage genetic variance explained. Positional candidate genes were those located within 50 kb of the top 1% of SNP windows explaining the most genetic variance. Of the 95 positional candidate genes, seven were further classified as functional candidate genes because of their association with both a significant gene ontology and molecular function term. The results of the GWAS emphasize the polygenic nature of the trait with no specific genomic region contributing a large portion to the overall genetic variance. Significant pathways relating to growth, muscle development, collagen formation, circulatory system development, cell response to stimulus, and cytokine production were identified. These results help to support published biological associations between WS and hypoxia and oxidative stress and provide information that may be useful for future-omics studies in understanding the biological associations with WS development in turkeys.

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White striping (WS) is a myopathy of growing concern to the turkey industry. It is rising in prevalence and has negative consequences for consumer acceptance and the functional properties of turkey meat. The objective of this study was to conduct a genome-wide association study (GWAS) and functional analysis on WS severity. Phenotypic data consisted of white striping scored on turkey breast fillets (N = 8422) by trained observers on a 0–3 scale (none to severe). Of the phenotyped birds, 4667 genotypic records were available using a proprietary 65 K single nucleotide polymorphism (SNP) chip. The SNP effects were estimated using a linear mixed model with a 30-SNP sliding window approach used to express the percentage genetic variance explained. Positional candidate genes were those located within 50 kb of the top 1% of SNP windows explaining the most genetic variance. Of the 95 positional candidate genes, seven were further classified as functional candidate genes because of their association with both a significant gene ontology and molecular function term. The results of the GWAS emphasize the polygenic nature of the trait with no specific genomic region contributing a large portion to the overall genetic variance. Significant pathways relating to growth, muscle development, collagen formation, circulatory system development, cell response to stimulus, and cytokine production were identified. These results help to support published biological associations between WS and hypoxia and oxidative stress and provide information that may be useful for future-omics studies in understanding the biological associations with WS development in turkeys. [ABSTRACT FROM AUTHOR]

ABSTRACT: White striping (WS) is an emerging myopathy that results in significant economic losses as high as $1 billion (combined with losses derived from other breast myopathies including woody breast and spaghetti meat) to the global poultry industry. White striping is detected as the occurrence of white lines on raw poultry meat. The exact etiologies for WS are still unclear. Proteomic analyses of co-expressed WS and woody breast phenotypes previously demonstrated dysfunctions in carbohydrate metabolism, protein synthesis, and calcium buffering capabilities in muscle cells. In this study, we conducted shotgun proteomics on chicken breast fillets exhibiting only WS that were collected at approximately 6 h postmortem. After determining WS severity, protein extractions were conducted from severe WS meat with no woody breast (WB) condition (n = 5) and normal non-affected (no WS) control meat (n = 5). Shotgun proteomics was conducted by Orbitrap Lumos, tandem mass tag (TMT) analysis. As results, 148 differentially abundant proteins (|fold change|>1.4; p-value < 0.05) were identified in the WS meats compared with controls. The significant canonical pathways included BAG2 signaling pathway, glycogen degradation II, isoleucine degradation I, aldosterone signaling in epithelial cells, and valine degradation I. The potential upstream regulators include LIPE, UCP1, ATP5IF1, and DMD. The results of this study provide additional insights into the cellular mechanisms on the WS myopathy and meat quality.

Background: There is a close relationship between breast muscle glucose metabolism, peripheral 5-hydroxytryptamine (5-HT), and myopathies in animals. Here, this study aimed to investigate the effects of different photoperiods on peripheral 5-HT metabolism, white striping (WS), and wooden breast (WB) in broilers. Methods: A total of 216 healthy 5-day-old (d) Arbor Acres (AA) male broilers were randomly assigned to 12L:12D, 18L:6D, and 24L:0D photoperiods for 4 weeks. Results: Compared with the 12L:12D photoperiod, we found the WB score in broilers was significantly increased in the 18L:6D and 24L:0D photoperiod at week 4 (p < 0.05). Muscle glycogen was significantly reduced (p < 0.05) and glycolysis was promoted in the breast muscles of broilers under the 18L:6D and 24L:0D photoperiods at week 2 and 4. Peripheral 5-HT concentrations, the mRNA expression of tryptophan hydroxylase 1 (TPH1) and serotonin transporter (SERT) in the cecal mucosa, and 5-hydroxytryptamine receptor 2A (5-HTR2A) mRNA expression in the breast muscle of broilers significantly up-regulated in the 18L:6D and 24L:0D photoperiod at week 2 and 4 (p < 0.05). Conclusions: Our findings revealed that extending the photoperiod improved the breast muscle growth rate, but up-regulated 5-HT synthesis and secretion to higher peripheral 5-HT, induced breast muscle glucose metabolism disorder, and increased WB incidence rates in broilers.

ABSTRACT: White striping (WS) is a common myopathy seen in fast-growing broilers. Studies have demonstrated that chitosan is effective as an antioxidant and has antiobesity and fat-absorption reduction properties. We hypothesized that the dietary supplementation of chitosan would have similar effects when fed to fast-growing broilers and would thus lower WS incidence and improve meat quality. One hundred twenty-six broilers were fed corn-soy diets. The grower and finisher diets contained either 0, 0.2, or 0.4% chitosan. After a 6 wk growth period, birds were euthanized, and then WS and gross pathology scores were assessed. Pectoralis major tissues were collected to evaluate cook loss, drip loss, histopathology scores, and the gene expression of CCR7, LECT2, CD36, PPARG, and PTGS2. There were no significant differences between the broiler weights, thus chitosan did not appear to compromise the overall growth of the broilers. Female broilers fed 0.4% chitosan had the lowest WS incidence, while male broiler fed 0.4% chitosan had the least cook loss. However, gene expression analyses did not offer insight into any grossly or histologically visualized differences in the muscles. Thus, while we can postulate that chitosan could have some positive effect in reducing WS incidence and improving meat quality, further studies are required to better scrutinize the mechanisms by which chitosan affects WS and other such myopathies in fast-growing broilers.

Background and Aim: The poultry industry faces an emerging muscular defect in chicken meat called white striping (WS). The biological processes associated with WS myopathy are immune system activation, angiogenesis, hypoxia, cell death, and striated muscle contraction. We examined the Troponin T3 (TNNT3), Toll-like receptor 2 (TLR2), and Toll-like receptor 4 (TLR4) genes based on their functions related to muscle contraction and the innate immune system. This study aimed to determine the muscle fiber characteristics (MFCs) and expression level of TNNT3, TLR2, and TLR4 genes in white striping chicken meat (WSCM). Materials and Methods: A total of 428 breast samples were randomly collected from a commercial poultry processing plant. The samples were classified into four levels: 0 (normal), 1 (moderate WS), 2 (severe WS), and 3 (extreme WS). Five samples per group were selected to evaluate MFCs, including total number of muscle fibers, muscle fiber diameter, cross-sectional area, endomysium thickness, and perimysium thickness. Five samples per group were selected for ribonucleic acid (RNA) isolation to evaluate the messenger RNA (mRNA) expression levels of TNNT3, TLR2, and TLR4 genes related to WS. Results: Statistical analysis revealed that the total number of fibers, endomysium thickness, and perimysium thickness significantly differed between groups (p < 0.05). Muscle fiber diameter and cross-sectional area did not significantly differ (p > 0.05). The expression of the TNNT3 gene did not significantly differ among groups (p > 0.05). Toll-like receptor 2 and TLR4 mRNA expression significantly differed among groups (p < 0.05). Conclusion: These detailed MFCs will provide baseline information to observe WS in chicken meat. Toll-like receptor 2 and TLR4 genes may play a role in the occurrence of WS in chicken meat through non-specific immune reactions.

Significant improvements in genetics, nutrition, and food efficiency have had a great impact on the rapid growth of broilers, notably with increases in muscle mass. However, with rapid growth, the broiler industry has been negatively impacted by the increased incidence of myopathies, including white striping. White striping affects the pectoralis major muscle of broilers, particularly the larger breasts of rapidly growing modern commercial broiler lines. In this study, we documented the growth process of commercial broiler chickens from hatching to market weight at 6 wk. Gross pathology and histopathology analyses were performed on pectoralis major muscle collected weekly from birds culled from 1 to 6 wk. The severity of both gross and histologic pathologies in the breast muscle increased over time. White striping was initially observed at week 2, with a rise in the incidence and severity through the sixth week. Mild histopathology was noted in week 2, characterized by macrophage infiltration and limited phagocytosis of the muscle. Muscle condition deteriorated with age and weight gain, with more prevalent macrophages, phagocytosis, and interstitial fibroblasts. By week 5 and 6, there was severe myopathy including regions of obliterated muscle tissue. Linear regression models show a positive correlation between white striping, gross pathology, and histopathology relative to weight and age.

Visual inspection is the prevailing practice in the industry for assessing white striping (WS) in broiler breast meat. However, this approach is subjective, laborious, and prone to error. Several studies have utilized imaging technology under uniform illumination; however, detecting defects, such as WS, remains challenging. This study investigated the efficacy of the emerging structured illumination reflectance imaging (SIRI) combined with deep learning (DL) for the WS assessment of broiler meat. Broiler fillets with varying degrees of WS were imaged using a custom-assembled monochromatic SIRI system (0.05-0.40 cycles/mm). The acquired SIRI pattern images were demodulated into direct components (DC) and amplitude components (AC) at each spatial frequency. Pre-trained DL models, including two Very Deep Convolutional Networks (VGG16 and VGG19) and two Densely Connected Convolutional Neural Networks (DenseNet121 and Denset- Net201), were evaluated as fine-tuned end-to-end classifiers and feature extractors separately to differentiate the meat samples. Fine-tuned VGG16 resulted in the best 2-class and 3-class classification accuracies of 94.5% and 74.6%, respectively, based on the AC images at 0.30 cycles/mm, improving over the accuracies of the corresponding DC images by 10.4% and 8.9%, respectively. Fine-tuned VGG19 and DenseNet201 also achieved substantial improvements of AC over DC images by 12% or higher. Linear discriminant analysis, in conjunction with principal component analysis for dimension reduction, yielded better accuracies of 96.6% in 2-class and 83.4% in 3-class classification, based on the deep features extracted by DenseNet121 from the AC images at 0.40 cycles/mm and 0.30 cycles/mm, respectively, representing improvements of 5.0% and 2.9% based on the features of the corresponding DC images. The SIRI technique combined with DL is effective for differentiating between normal and WS-affected broiler meat. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study was carried out to investigate the influence of genotype and housing systems on the incidence of white striping, proximate composition, and sensory analysis of broiler breast meat. In total, 10 random breast muscle samples of male broilers from each of 6 interactive groups (fast and slow-grow!ng bro!lers × deep l!tter, fully slatted "oor!ng and free-range hous !ng; 2 × 3:6), slaughtered at 56 days old, were collected and analyzed in the study. The proximate composition analysis was evaluated using the AOAC Official Methods of Analysis. The occurrence of white striping was determined by examining the pectoral muscles of the broiler in the groups. A 9-point hedonic scale was used for sensory analysis of meat samples. The crude ash, crude fat content, and cooking loss values of the fast-growing broilers meat samples were found greater than slow-growing broilers' meat (p < .02, p < .001, and p < .033), while meat samples of slow-growing broiler had significantly higher crude protein and water-holding capacity values (p < .001 and p < .002). The crude fat content of free-range meat and crude protein of the meat produced from the slatted floors were significantly greater than the others (p < .001 and p < .043). The prevalence of white striping in breast meat in fast-growing broilers was significantly greater than that of slow-growing broilers. The meat produced from the slatted floor had significantly greater values for odor intensity, flavor intensity, and overall acceptability than the meat produced from free-range and deep litter housing (p < .012, p < .017, and p < .006). In conclusion, it can be said that the housing system, genotype, and genotype × housing system interactions affected the broiler's breast meat quality characteristics. All nutritional characteristics of broiler breast meat and the occurrence of white striping are significantly affected by genotype. Planning further research in commercial conditions should be more useful to see the comprehensive effects of the factors investigated in this experiment. [ABSTRACT FROM AUTHOR]

With an increase in the demand and production of chicken products, broilers have been bred to grow larger at a faster rate. This has led to several myopathies, one of which being white striping, which is now common to almost all broilers and is characterized as the deposition of fat within the broiler breast muscles. The purposes of this review are to examine the change in chicken production over the years, and to consider normal muscle growth physiology and the suspected pathological process and causes of white striping, as well as white striping visualization and detection in fast-growing broilers. With the increase in growth rate and size, multiple biochemical processes are affected in broilers, leading to hypoxia and inflammation, subsequent formation of foam cells from macrophages, and the deposition of fat in the form of white stripes along the muscle tissues. The negative effects of white striping include increased fat content and calories and decreased protein content, as well as reductions in palatability and drip loss. Thus, this review also explores the effects of white striping on meat quality, and finally evaluates several strategies attempted to mitigate white striping.

The current study investigated the effects of intermittent feeding (IF) and fasting strategies at different times post–hatch on muscle growth and white striping (WS) breast development. In the first trial, 32 one-day-old Abor Acre broilers were fed ad libitum (AL) for 3 d post–hatch and then randomly allotted into 4 feeding strategies including AL, 1h-IF group (1 h IF, 4 times feeding/d, 1 h each time), 1.5h-IF (1.5 h IF, 4 times feeding/d, 1.5 h each time), and fasting (1d acute fasting, 6 d free access to feed) groups and fed for 7 d. Although angiogenic genes including VEGFA, VEGFR1, and VEGFR2, and myogenic genes including MYOG and MYOD were upregulated (P 0.05). In the second trial, 384 one-day-old birds were fed AL for 1 wk and then randomly allotted to the above 4 feeding strategies starting at 8 d of age until 42 d of age. Similarly, IF and fasting strategies upregulated the expression of angiogenic and myogenic genes (P 0.05). Fasting and 1h-IF reduced the expression of adipogenic genes ZNF423 and PDGFRα (P

Myopathies of the breast muscle in broiler chickens are a great concern of modern poultry production because of the economic losses associated with the waste of unfit meat, the effects on meat nutritional quality for food and on meat technological quality for processing, and last, but not less important, the effects on animal welfare and health. Largely spread in fast-growing genotypes, these muscle defects have a low hereditability for which genetic selection for their control seems to be a weak strategy or, at least, a weak long-term strategy. On the other hand, several investigations have been performed on the physiological mechanisms triggering the onset and the evolution of myopathies, and different non-genetic strategies have been proposed to control their in vivo occurrence. Thus, the present paper aimed to analyse the scientific literature investigating the effects of feeding and nutritional strategies on the occurrence of myopathies to find out the most tested strategies, the most promising ones and, in perspective, strengths and weakness of the same strategies. [ABSTRACT FROM AUTHOR]

With an increase in the demand and production of chicken products, broilers have been bred to grow larger at a faster rate. This has led to several myopathies, one of which being white striping, which is now common to almost all broilers and is characterized as the deposition of fat within the broiler breast muscles. The purposes of this review are to examine the change in chicken production over the years, and to consider normal muscle growth physiology and the suspected pathological process and causes of white striping, as well as white striping visualization and detection in fast-growing broilers. With the increase in growth rate and size, multiple biochemical processes are affected in broilers, leading to hypoxia and inflammation, subsequent formation of foam cells from macrophages, and the deposition of fat in the form of white stripes along the muscle tissues. The negative effects of white striping include increased fat content and calories and decreased protein content, as well as reductions in palatability and drip loss. Thus, this review also explores the effects of white striping on meat quality, and finally evaluates several strategies attempted to mitigate white striping. [ABSTRACT FROM AUTHOR]

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.

Conventional broiler diets include synthetic methionine to optimize fast muscle growth. Recently, a conventional synthetic methionine-rich diet was compared to alternative diet regimens providing natural sources of methionine. Broilers fed diets with natural methionine sources grew at a slightly slower rate. From this study, we hypothesized that the difference in a growth rate would be reflected in features of the breast muscle from broilers fed the alternative diet. We hypothesized that white striping of pectoralis major muscle would be reduced in slower growing broilers fed the alternative diet regimen with natural methionine. We also hypothesized that there would be associated differences in gene expression for cell differentiation and pathology markers. Broilers fed a conventional corn/soy diet regimen with synthetic methionine were compared to those fed roasted cowpea and sunflower seed meal (60% corn/soy, 20% sunflower seed meal, and 20% roasted cowpea) and no synthetic methionine. Overall broiler growth, muscle gene expression, and muscle collagen content data were compared. Expression analyses of combinations of MYOD1, PPARG, COL1A2, TRIM63, SOD1, PTGS2, and CD36 genes were used to examine differentiation and inflammation in the pectoralis muscles. The group fed an alternative diet gained less weight than those fed the control diet in the starter and grower phases but not in the finisher phase. Ultimately, the conventional diet resulted in a greater final weight for the broilers. However, mean white striping scores for the pectoralis major muscles were greater in the conventional control diet regimen. Gene expression results indicated greater expression of PPARG, PTGS2, and CD36 in the muscle of broilers fed the control diet. These data associate white striping with fat deposition and inflammation. Thus, whether due to differences in feed intake, growth rate, or actual compositional differences, the alternative diet with natural methionine sources seemed to curtail amounts of white striping in broiler muscle. More studies are necessary to further discern the effect of growth rate and natural methionine sources on white striping.

ABSTRACT: The woody breast (WB) myopathy is an unintended outcome of fast broiler chicken growth and high breast muscle yields. Myodegeneration and fibrosis in the living tissue are results of hypoxia and oxidative stress driven by lack of blood supply to muscle fibers. The study aim was to titrate a vasodilator ingredient, inositol-stabilized arginine silicate (ASI), as a feed additive to improve blood flow and ultimately, breast meat quality. A total of 1,260 male Ross 708 broilers were assigned to: 1) a control basal diet, or the control diet plus increasing ASI: 2) 0.025% ASI, 3) 0.05% ASI, 4) 0.10% ASI, or 5) 0.15% ASI. At d 14, 28, 42, and 49, growth performance was measured on all broilers and serum from 12 broilers/diet was analyzed for creatine kinase and myoglobin presence. On d 42 and 49, 12 broilers/diet were measured for breast width, then left breast fillets were excised, weighed, palpated for WB severity, and visually scored for degree of white striping (WS). At 1 d postmortem, 12 raw fillets/treatment underwent compression force analysis, and at 2d postmortem, the same fillets were analyzed for water-holding capacity. mRNA was isolated from 6 right breasts/diet at both d 42 and 49 for qPCR quantification of myogenic gene expression. Birds fed the lowest dose of 0.025% ASI had a 5-point/3.25% feed conversion ratio reduction compared to birds fed 0.10% ASI over wk 4 to 6 and reduced serum myoglobin at 6-wk of age compared to the control. Breasts from birds fed 0.025% ASI received 42% greater normal WB scores at d 42 compared to control fillets. At d 49, breasts from broilers fed 0.10 and 0.15% ASI received 33% normal WB scores. At d 49, 0.025% AS-fed broiler breasts showed no severe WS. Increased myogenin expression was observed in 0.05 and 0.10% ASI breast samples on d 42 and myoblast determination protein-1 expression was upregulated in breasts from birds fed 0.10% ASI on d 49 compared to the control. Therefore, a dietary inclusion of 0.025, 0.10, or 0.15% ASI was beneficial in reducing WB and WS severity and promoting muscle growth factor gene expression at age of harvest without diminishing bird growth or breast muscle yields.

ABSTRACT: The objective of this study was to compare the meat quality characteristics and collagen-related gene expression levels in the broiler pectoralis major (PM) muscle among the meat quality groups, including normal, pale, soft, and exudative (PSE), and white striping (WS) groups. The group was classified by their WS degree (moderate or severe striping) and quality traits including pH and lightness values at 24 h postmortem (normal group: pH24 h ≥5.7, 48≤L*≤53, without WS features; PSE group: pH24 h 53, without WS features; WS group: pH24 h ≥5.7, 48≤L*≤53, with moderate or severe striping). The WS group revealed no differences in all measured meat quality traits compared to the normal group (P > 0.05). PM muscles exhibiting PSE conditions without WS indicated lower pH15 min and pH24 h values (P < 0.05). Whereas, lower lightness and cooking loss values were observed in the normal and WS groups compared to the PSE group (P < 0.05). No significant difference was observed in the level of type I collagen among the groups (P > 0.05), whereas a higher type III collagen level was observed in the WS group than in the other groups (P < 0.05). Additionally, the WS group showed a higher type IV collagen level compared to the normal group (P < 0.05) and a level not different from that of the PSE group (P > 0.05). In contrast, the expression levels of matrix metalloproteinase (MMP) 2, involved in type IV collagen degradation, and angiopoietin-like protein 7, associated with collagen accumulation, were higher in the WS group compared to the normal group (P < 0.05). However, no difference was detected in the MMP1 level among the all groups (P > 0.05). These results suggest that the occurrence of WS features in broiler PM muscle, unlike PSE and normal conditions, can be influenced by the expression levels of collagen-related genes associated with abnormalities in extracellular matrix components.

ABSTRACT: Genetic selection for breast yields and fewer days to market has inadvertent effects on broiler meat quality. Woody breast (WB) and white striping (WS) are pectoralis major myopathies prevalent in commercial broilers. Effects of voluntary exercise on these disorders, specifically, are unknown. A second-generation laser enrichment device shown to induce activity in Ross 308 and 708 birds was implemented using 1,360 Ross 708 broilers randomly assigned to laser enrichment or control for 49 d. Laser-enriched birds were exposed to 6-min laser periods 4 times daily. Seventy focal birds were gait and contact dermatitis scored weekly. Blood was collected wk 5 to 7 from 56 broilers for serum corticosterone, myoglobin, and troponin. Seventy broilers were sampled for breast muscle width, fillet dimensions, and WB and WS at wk 6 and 7. One and 2-day postmortem, fillet compression force and water-holding capacity were measured. Serum corticosterone was reduced by up to 21% in laser-enriched birds wk 5 to 7 (P < 0.01). Serum myoglobin was increased in laser-enriched broilers by 5% on wk 5 (P < 0.01) but increased in control birds wk 6 to 7 by up to 13% (P < 0.01). Serum troponin was reduced in laser-enriched broilers by 9% at wk 5 (P < 0.01). Laser exposure increased breast width and fillet weight at d 42 by 1.08 cm (P < 0.05) and 30 g (P < 0.05). At d 49, fillet height was increased 0.42 cm in laser-enriched birds (P < 0.05). Laser enrichment reduced severe WS incidence at d 42 by 24% (P < 0.05) and on d 49 by 15% (P < 0.10). Severe WB score was numerically reduced by 11% in laser enrichment on d 42 and 18% on d 49 (P > 0.05). Water-holding capacity was improved in laser-enriched breasts (P < 0.01) and expression of myostatin and insulin-like growth factor 2 were increased on d 49 (P ≤ 0.01. Laser enrichment reduced markers of stress and muscle damage while improving breast muscle quality and is therefore a potential effective enrichment for commercial broilers.

SUMMARY: Performance and processing advantages have been noted in meat animal production when excess arginine is available in the diet. In addition, dietary inclusion of guanidinoacetic acid (GAA) has provided insight on sparing arginine for broiler chickens. Therefore, a study was conducted to assess dietary inclusion of GAA on broiler breast myopathy prevalence. Dietary treatments were established using a control basal diet fed over four feeding phases and treatments were allocated as an additional supplementation of 0.06% (GAA 0.06) and 0.12% (GAA 0.12) in the form of CreAMINO (Alzchem Group, Trostberg, Germany). Bi-weekly BW, body weight gain (BWG), feed intake (FI), and mortality corrected FCR were calculated throughout growing phase. Broilers were processed to determine part yields, with breast and tenders being scored for myopathies. Both GAA treatments improved FCR (P < 0.05) compared to the control diet at 55 d. No differences (P > 0.05) were observed for BW or BWG throughout the growout period. At day of processing, no differences were observed in yields (P > 0.05). For woody breast (WB) and woody-like tender (WT), the control produced higher mean scores (P < 0.05) when compared to GAA 0.12. For white striping (WS), the control and GAA 0.06 expressed higher mean scores (P < 0.05) than GAA 0.12. No differences were observed in tender feathering (TF; P > 0.05). The results of this experiment indicate that GAA supplementation in broiler diets may be an effective tool for improving meat quality by reducing myopathy severity, without negatively affecting growth performance.

ObjectiveThis study aimed at investigating white striping (WS) and wooden breast (WB) cases in breast meat collected from commercial broilers.MethodsA total of 183 breast samples were collected from male Ross 308 broilers slaughtered at the age of 6 weeks (n = 100) and 7 weeks (n = 83). The breasts were subjected to meat defect inspection, meat quality determination and histology evaluation.ResultsOf 183, 4 breasts from 6-week-old broilers were classified as non-defective while the others exhibited the WS lesion. Among the 6-week-old birds, the defective samples from the medium size birds (carcass weight ≤2.5 kg) showed mild to moderate WS degree with no altered meat quality. Some of the breasts from the 6-week-old birds with carcass weight above 2.5 kg exhibited WB in accompanied with the WS condition. Besides of a reduction of protein content, increases in collagen matter and pH values in the defective samples (p

White striping (WS) is the most common myopathy in the broiler chicken industry. To reveal flavor changes of WS meat objectively, flavor precursors of WS breast muscle were evaluated systematically with integrated metabolomics and lipidomics. The results showed that WS could be distinguished from normal controls by E-nose, and four volatile compounds (o-xylene, benzene, 1,3-dimethyl, 2-heptanone and 6-methyl and Acetic acid and ethyl ester) were detected as decreased compounds by gas chromatography-mass spectrometry. Lipidomic analysis showed that WS breast fillets featured increased neutral lipid (83.8%) and decreased phospholipid molecules (33.2%). Targeted metabolomic analysis indicated that 16 hydrophilic metabolites were altered. Thereinto, some water-soluble flavor precursors, such as adenosine monophosphate, GDP-fucose and L-arginine increased significantly, but fructose 1,6-bisphosphate and L-histidine significantly decreased in the WS group. These results provided a systematic evaluation of the flavor precursors profile in the WS meat of broiler chickens. [ABSTRACT FROM AUTHOR]

BACKGROUND: White striping (WS) is a myopathy of breast muscle (Pectoralis major) that affects the quality and consumer acceptance of breast fillets of broiler chickens. Previous studies have shown that intermittent dilution of dietary nutrients suppresses the development of WS on the breast muscle of broiler chickens. However, the mechanism by which these interventions reduce the occurrence of WS remains inconclusive. In this study, we adopted intermittent reduction of dietary digestible lysine (dLys) density or metabolizable energy (ME) and amino acid (AA) density using chemical and fatty acid composition of breast fillets, and blood metabolites to understand the mechanism while histopathology and immunohistochemistry of breast muscles were used for confirmation. RESULTS: Occurrence of WS was lower in broiler chickens fed 85% dLys diets in comparison with other groups. Crude protein and ether extract in breast meat of 85% dLys groups were greater (P < 0.001) and lower (P = 0.010), respectively. Serum concentrations of lipid metabolites and enzymes were lower in broiler chickens fed 85% dLys diets than control group (P < 0.05). Feeding 85% dLys diets had low degree of myodegeneration and necrosis, inflammation, lipid deposition, infiltration of T‐lymphocyte (CD3+) and macrophages (Iba‐1+), and low expression of heat‐shock protein 70 (HSP70) than other groups (P < 0.001). CONCLUSION: Dilution of dietary dLys to 85% of the required quantities reduces the development of WS in broiler chickens by slowing the growth, lipid synthesis, and muscle damage confirmed by lower extent of histopathological lesions. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Simple Summary: In recent years, there has been growing interest in the use of thyme and oregano essential oils in feed formulations to promote growth in chicken broilers. Thyme and oregano essential oils are considered promising ingredients to replace antibiotics as growth promotors. The aim of this study was to evaluate the impact of thyme and oregano essential oils on growth performance, broiler health, and the incidence of muscle abnormalities at different slaughter ages. This study showed that the addition of thyme and oregano essential oils, individually or in combination, significantly increased body weight compared to the control group. Thyme and oregano essential oils improved the feed conversion factor, which indicates lower feed intake (feed intake did not change according to our results) with higher meat production. Muscle abnormalities increased with the addition of thyme and oregano essential oils to broiler diets, which could be due to the increase in the growth rate. In conclusion, the inclusion of thyme and oregano oils in broiler chicken feed resulted in an improvement in the growth performance of broiler chickens. The objective of this study was to investigate the effects of thyme and oregano essential oils (as growth promotors), individually and in combination, on the health, growth performance, and prevalence of muscle abnormalities in broiler chickens. Six hundred day-old Cobb 500 hybrid chickens were randomized into four dietary treatment groups with three replicates each. Chicks in the control group (C) received a basal diet, while the experimental treatment groups received basal diets containing 350 mg/kg of thyme oil (T1), 350 mg/kg of oregano oil (T2), and 350 mg/kg of thyme and oregano oil (T3). Growth performance parameters were evaluated at 14, 28, and 42 days. The broilers in treatments T1 and T2 had significantly higher body weights than the control group. The feed conversion ratio was the lowest in chicks who received oregano oil, followed by those fed thyme oil. The overall prevalence of growth-related breast muscle abnormalities (including white striping and white striping combined with wooden breast) in groups receiving essential oils (T1, T2, and T3) was significantly higher than in the control group (C). The thyme and oregano oil diets showed no significant differences in antibody titers against Newcastle disease or interferon-γ (INF-γ) serum levels. In conclusion, thyme and oregano oils had a positive impact on the growth performance of broiler chickens but increased the incidence of growth-related breast muscle abnormalities. [ABSTRACT FROM AUTHOR]

Growth-related abnormalities affecting modern chickens, known as White Striping (WS) and Wooden Breast (WB), have been deeply investigated in the last decade. Nevertheless, their precise etiology remains unclear. The present study aimed at providing new insights into the molecular mechanisms involved in their onset by identifying clusters of co-expressed genes (i.e., modules) and key loci associated with phenotypes highly related to the occurrence of these muscular disorders. The data obtained by a Weighted Gene Co-expression Network Analysis (WGCNA) were investigated to identify hub genes associated with the parameters breast width (W) and total crude protein content (PC) of Pectoralis major muscles (PM) previously harvested from 12 fast-growing broilers (6 normal vs. 6 affected by WS/WB). W and PC can be considered markers of the high breast yield of modern broilers and the impaired composition of abnormal fillets, respectively. Among the identified modules, the turquoise (r = -0.90, p < 0.0001) and yellow2 (r = 0.91, p < 0.0001) were those most significantly related to PC and W, and therefore respectively named “protein content” and “width” modules. Functional analysis of the width module evidenced genes involved in the ubiquitin-mediated proteolysis and inflammatory response. GTPase activator activity, PI3K-Akt signaling pathway, collagen catabolic process, and blood vessel development have been detected among the most significant functional categories of the protein content module. The most interconnected hub genes detected for the width module encode for proteins implicated in the adaptive responses to oxidative stress (i.e., THRAP3 and PRPF40A), and a member of the inhibitor of apoptosis family (i.e., BIRC2) involved in contrasting apoptotic events related to the endoplasmic reticulum (ER)-stress. The protein content module showed hub genes coding for different types of collagens (such as COL6A3 and COL5A2), along with MMP2 and SPARC, which are implicated in Collagen type IV catabolism and biosynthesis. Taken together, the present findings suggested that an ER stress condition may underly the inflammatory responses and apoptotic events taking place within affected PM muscles. Moreover, these results support the hypothesis of a role of the Collagen type IV in the cascade of events leading to the occurrence of WS/WB and identify novel actors probably involved in their onset. [ABSTRACT FROM AUTHOR]

Fast-growing broiler chickens are subjected to breast myopathies such as white striping (WS), wooden breast (WB), and spaghetti meat (SM). Available studies about risk factors for myopathy occurrence often used flock data whereas a few reports evaluated chicken individual data. Thus, the present study aimed to elucidate the effect of growth and slaughter traits, besides sex and genotype on myopathy occurrence. Data were obtained from eight experimental trials, which used a total of 6,036 broiler chickens. Sex, genotype, daily weight gain, slaughter weight, and breast yield were evaluated as potential risk factors by logistic regression analyses. Then, the effects of myopathy and sex were evaluated on meat rheological traits (pH, colour, cooking losses and shear force). Based on a logistic regression, WS occurrence was associated with genotype, breast weight, and breast yield. Compared with chickens with intermediate breast weight and breast yield, higher odds of having WS were found in chickens with high breast weight (OR: 1.49) and yield (OR: 1.27), whereas lower odds were found in those with low breast weight (OR: 0.57) and yield (OR: 0.82). As for WB and SM, females had lower odds of having WB (OR: 0.55) and higher odds of showing SM (OR: 15.4) compared to males. In males, higher odds of having WBwere found in chickens with a high daily weight gain (OR: 1.75) compared to those with an intermediate daily weight gain. In females, higher odds of having SM were associated to a high slaughter weight (OR: 2.10) while lower odds to a low slaughter weight (OR: 0.87). As for meat quality, only WB meat was clearly different for some technological and sensorial properties, which can play a major role also in meat processing. In conclusion, our analysis identified breast development as a potential risk factor for WS, while a high growth was the risk factor for WB and SM. A different probability of having WB or SM in females and male was found. [ABSTRACT FROM AUTHOR]

Fast-growing broiler chickens are subjected to breast myopathies such as white striping (WS), wooden breast (WB), and spaghetti meat (SM). Available studies about risk factors for myopathy occurrence often used flock data whereas a few reports evaluated chicken individual data. Thus, the present study aimed to elucidate the effect of growth and slaughter traits, besides sex and genotype on myopathy occurrence. Data were obtained from eight experimental trials, which used a total of 6,036 broiler chickens. Sex, genotype, daily weight gain, slaughter weight, and breast yield were evaluated as potential risk factors by logistic regression analyses. Then, the effects of myopathy and sex were evaluated on meat rheological traits (pH, colour, cooking losses and shear force). Based on a logistic regression, WS occurrence was associated with genotype, breast weight, and breast yield. Compared with chickens with intermediate breast weight and breast yield, higher odds of having WS were found in chickens with high breast weight (OR: 1.49) and yield (OR: 1.27), whereas lower odds were found in those with low breast weight (OR: 0.57) and yield (OR: 0.82). As for WB and SM, females had lower odds of having WB (OR: 0.55) and higher odds of showing SM (OR: 15.4) compared to males. In males, higher odds of having WB were found in chickens with a high daily weight gain (OR: 1.75) compared to those with an intermediate daily weight gain. In females, higher odds of having SM were associated to a high slaughter weight (OR: 2.10) while lower odds to a low slaughter weight (OR: 0.87). As for meat quality, only WB meat was clearly different for some technological and sensorial properties, which can play a major role also in meat processing. In conclusion, our analysis identified breast development as a potential risk factor for WS, while a high growth was the risk factor for WB and SM. A different probability of having WB or SM in females and male was found.

Growth-related abnormalities affecting modern chickens, known as White Striping (WS) and Wooden Breast (WB), have been deeply investigated in the last decade. Nevertheless, their precise etiology remains unclear. The present study aimed at providing new insights into the molecular mechanisms involved in their onset by identifying clusters of co-expressed genes (i.e., modules) and key loci associated with phenotypes highly related to the occurrence of these muscular disorders. The data obtained by a Weighted Gene Co-expression Network Analysis (WGCNA) were investigated to identify hub genes associated with the parameters breast width (W) and total crude protein content (PC) of Pectoralis major muscles (PM) previously harvested from 12 fast-growing broilers (6 normal vs. 6 affected by WS/WB). W and PC can be considered markers of the high breast yield of modern broilers and the impaired composition of abnormal fillets, respectively. Among the identified modules, the turquoise (r = -0.90, p < 0.0001) and yellow2 (r = 0.91, p < 0.0001) were those most significantly related to PC and W, and therefore respectively named “protein content” and “width” modules. Functional analysis of the width module evidenced genes involved in the ubiquitin-mediated proteolysis and inflammatory response. GTPase activator activity, PI3K-Akt signaling pathway, collagen catabolic process, and blood vessel development have been detected among the most significant functional categories of the protein content module. The most interconnected hub genes detected for the width module encode for proteins implicated in the adaptive responses to oxidative stress (i.e., THRAP3 and PRPF40A), and a member of the inhibitor of apoptosis family (i.e., BIRC2) involved in contrasting apoptotic events related to the endoplasmic reticulum (ER)-stress. The protein content module showed hub genes coding for different types of collagens (such as COL6A3 and COL5A2), along with MMP2 and SPARC, which are implicated in Collagen type IV catabolism and biosynthesis. Taken together, the present findings suggested that an ER stress condition may underly the inflammatory responses and apoptotic events taking place within affected PM muscles. Moreover, these results support the hypothesis of a role of the Collagen type IV in the cascade of events leading to the occurrence of WS/WB and identify novel actors probably involved in their onset.

Large variations in hatching egg incubation temperatures have been previously shown to negatively impact posthatch growth in broiler chickens. The objective was to determine whether small incubation temperature variations owing to incubator tray location (LOC) could alter posthatch female and male broiler growth performance and carcass characteristics. Broiler hatching eggs were obtained from a 40-week-old commercial broiler breeder flock and incubated in trays placed in the bottom (BOT), middle (MID), and top (TOP) thirds of the racks (n = 4 racks per incubator tray LOC) in a single-stage incubator in a commercial hatchery. Chicks hatched from the 3 LOC (n = 720 per LOC) were vent sexed, vaccinated, and separate-sex reared with 12 birds per pen in a floor-pen facility and fed a common corn and soybean meal–based diet for 41 d. At day 41, all birds (n = 720) were processed to determine carcass and carcass part yields and incidence and severity of the meat quality defects wooden breast (WB) and white striping (WS). No LOC × Sex interactions were observed (P > 0.05). Growth performance and incidence and severity of WB and WS were similar among LOC (P > 0.05). However, broilers from BOT trays had heavier tender and breast weights than broilers from warmer MID trays (P

The effect of docosahexaenoic acid (DHA, 22:6 n-3)-rich microalgae and methionine (Met) supplementation on production performance, incidence of breast muscle white striping (WS), and pathology, lipid profile, and meat quality aspects in broiler chickens was investigated. The hypothesis tested was that feeding Met and n-3 fatty acid (FA)-rich diet enhances muscle n-3 FA content and meat quality while attenuating breast muscle WS and myopathy in broiler chickens. One hundred and forty four (n = 144) 10-day-old Cornish cross chicks were fed a corn-soybean meal-based diet containing 0% microalgae (control), 2% microalgae (diet 1), and diet 1 + 100% more National Research Council requirement of Met (diet 2) up to day 42 of growth. All diets were isocaloric and isonitrogenous. The chicks were kept in 6 pens with 8 chicks per replicate pen. Feed consumption and feed efficiency were calculated on day 21 and 42. On day 43, 3 chicks per pen (n = 18/treatment) were euthanized. The breast muscle (pectoralis major) was visually scored for muscle WS (1 = no striping, 2 = mild, 3 = severe) and was subjected to histopathology. Breast muscle lipid profile (total lipids, FA composition, cholesterol, lipid oxidation products), quality (moisture, color, drip loss, shear force, cook loss, pH), and chemical characterization (protein, minerals) were recorded. A one-way analysis of variance was carried out with diet as the main factor and significance was set at P < 0.05. The incidence of muscle WS was lower (P < 0.02) for control vs. diet 2 and a trend for reduction in WS was observed in birds fed diet 1 vs. control (P = 0.09). Histopathological changes consisted of floccular or vacuolar degeneration, fibrosis, lipidosis, interstitial inflammation, and lysis of fibers, and were minimal in diet 2 when compared to control (P < 0.05). The total lipid content was lowest in birds fed diet 1 (P < 0.05). Total n-3 and total long chain (≥20C) n-3 FA were highest in the breast muscle of diet 2 birds (P < 0.05). Muscle drip loss and shear force were highest in diet 2 (P < 0.05). Meat color (a∗, redness) was reduced (P < 0.05) and a trend for reduction in b∗ (yellowness) was observed in diet 2 (P = 0.07). No effect of diet on body weight gain, feed efficiency, breast muscle yield, pH, moisture, lipid oxidation products, cook loss, minerals (Ca, P, Mg, Na), cholesterol, or protein content was observed (P > 0.05). The results demonstrated a significant effect of DHA-rich microalgae along with Met supplementation in reducing the incidence of breast muscle striping and myopathy, while enriching meat with n-3 FA. However, inclusion of Met in microalgae-based diets could influence meat tenderness and color.

Context: Barley can be included in poultry diets as a cost-effective energy-contributing ingredient. However, its inclusion in meat chicken diets is limited because it is considered a viscous grain due to high crude fibre and soluble non-starch polysaccharide contents. Aims: The study quantified the optimum inclusion rate of barley in meat chicken diets during different growing phases, using an incremental program. Methods: Eight dietary treatments followed a 4 × 2 factorial arrangement, with three levels of barley inclusion to a wheat-based diet, and a nil-barley control, with or without β-glucanase supplementation. Barley was initially included at 0% (low), 7.5% (medium) and 15% (high) in starter diets (Days 1–9), scaling up by 7.5% for each level in grower (Days 9–21), finisher (Days 23–35) and withdrawal (Days 35–42) diets. Each diet was fed ad libitum to six replicate pens of 18 chicks. On Day 42, four birds per replicate pen were euthanised to determine carcass yield and collect digesta. Key results: During the starter period, a significant (P < 0.05) barley × β-glucanase interaction resulted in lower bodyweight gain (8%) and higher feed conversion ratio (8.5 points) at 15% barley inclusion without β-glucanase, whereas performance was restored with β-glucanase supplementation. No treatment interaction was apparent on growth performance assessed over the entire production period (Days 1–42). Barley inclusion at medium and high levels increased bodyweight gain, and at all levels improved feed efficiency (P < 0.01) compared with the control. β-Glucanase improved (P < 0.05) feed efficiency. Highest (P < 0.01) breast meat yield was measured for diets with medium barley inclusion. There were no interactive or main effects on duodenal digesta viscosity. Barley inclusion increased distal ileal digesta water content by ∼8–10% (P < 0.05). Conclusions: Incremental inclusion of barley from 15% in a starter diet, scaling up to 37.5% in a withdrawal diet, does not compromise growth performance or carcass yields in broiler chickens. β-Glucanase supplementation favours both bodyweight gain and feed efficiency. Medium level of barley inclusion favours breast meat yield. Implications: Barley can be considered an economical grain to formulate cost-effective diets for broiler chickens. An incremental program is a practical approach to optimise barley inclusion rate. Barley is an alternative grain to wheat in Australian meat chicken diets, and often cheaper. However, the presence of some anti-nutritional factors in barley means that the grain is used at limited levels in the diet. Our results indicate that an incremental program is an effective approach to optimise barley inclusion rate in meat chicken diets, to formulate more cost-effective finished feeds and add value to Australian barley, particularly when export markets become precarious. [ABSTRACT FROM AUTHOR]

A 49-day trial was conducted to determine the impact of dietary amino acid (AA) density and stocking density (SD) on growth performance, carcass traits, meat quality, and white striping (WS) occurrence in broiler chickens. Two hundred eighty-eight Ross 308 male broilers consisting of 6 replicate cages with 8 broilers per replicate were used. Treatments were arranged in a 3 × 2 factorial and consisted of 3 AA densities (normal, 10, or 20% lower than normal) and 2 different SD (high 35 kg/m2 or low 26 kg/m2). Breasts were classified as normal, moderate, and severe for WS. Data were analyzed as a completely randomized design using the GLM procedure. Decreasing AA density decreased overall growth performance, carcass, breast yields, and fillet dimensions linearly, while leg and rib cage yields increased linearly (P

Woody breast (WB) myopathy is a major concern and economic burden to the poultry industry, and for which, there is no effective solution because of its unknown etiology. In a previous study, we have shown that phytase (Quantum Blue, QB) reduces the WB severity by 5% via modulation of oxygen homeostasis-related pathways. As WB has been suggested to be associated with lipid dysmetabolism, we aimed to determine the effect of QB on WB and breast muscle fatty acid profile. Male broilers were subjected to 6 treatments (96 birds/treatment): a nutrient adequate control group (PC), the PC supplemented with 0.3% myo-inositol (PC + MI), a negative control (NC) deficient in available P and Ca by 0.15 and 0.16%, respectively, the NC fed with QB at 500 (NC+500 FTU), and 1,000 (NC+ 1,000 FTU) or 2,000 FTU/kg of feed (NC+2,000 FTU). Woody breast and white striping scores were recorded, and fatty acid profiles were determined using gas liquid chromatography. Woody breast-affected muscles exhibited a significant higher incidence of white striping as liquid chromatography analysis reveals an imbalance of fatty acid profile in the breast of WB-affected birds with a significant higher percent of saturated fatty acids (SFA, myristic [14:0], pentadecanoic [15:0], and margaric [17:0]) and monounsaturated fatty acids (myristoleic [14:1], palmitoleic [16:1c], 10-trans-heptadecenoic [17:1t], oleic [18:1c9], and vaccenic [18:1c11]), and lower content of polyunsaturated fatty acids (PUFA) and omega-3 (P

White striping (WS) and woody breast (WB) have been previously associated with older and heavier birds. However, there is limited information supporting the association between these 2 muscle conditions and growth parameters. The objectives of this study were 1) to investigate the relationship between WS and WB using different growth production factors and 2) to propose a predictive model that uses growth production factors to investigate the incidence and severity of WS and WB. A combined database of 4,332 broilers pooled from 7 research experiments conducted from 2016 to 2017 at Texas A&M University was used in this study. Parameters such as sex, age (4 wk, 6 wk, and 8 wk), strain (standard A vs. high-breast-yield [B and C]), live weight categories (500 g increments), and breast weight categories (250 g increments) were included in the model. Results showed that WS was 12% more likely to be present in non-WB fillets. The association between WS and WB suggests a moderate relationship between the ranks of both outcome variables (ρ = 0.57, P < 0.0001). Variables such as age, live weight, and sex were not as important as breast weight and strain in the severity prediction of WS and WB. Butterfly fillets above 750 g and with high-breast-yielding strains were more likely associated with higher severity of WS and WB scores. No post hoc variable selection was performed. Both models show good discrimination. The WS model produced an uncorrected area under the curve (AUC) of 0.739, with a bootstrap corrected estimate of 0.736. The WB model produced an uncorrected AUC of 0.753 and a bootstrap corrected estimate of 0.752. Therefore, the growth production factors analyzed in this study indicated that there is a moderate relationship between WS and WB myopathies and were jointly predictive of the severity of WS and WB. Potentially other factors not included in this study may play a major role in the relationship of these 2 myopathies. More research should be done to investigate this possibility.

ABSTRACT: The aim of this study was to evaluate possible changes in the quality of chicken breast meat containing white stripes during freezing for 12 mo. Samples of Pectoralis major muscle from male Cobb 500 broilers containing white stripes in moderate and severe degrees were used, as well as samples from a control group (normal – absence of myopathies). Part of the samples (n = 60; n = 20 for each severity degree) were analyzed on the day of collection (beginning) and the rest (n = 240) was frozen (−20°C) for up to 12 mo. At the end of each proposed freezing period (3, 6, 9, and 12 mo), color, pH, water holding capacity, cooking loss, tenderness, lipid oxidation, chemical composition, cholesterol and collagen concentrations, myofibrillary fragmentation, and sarcomere length were analyzed. Microbiological analysis of samples was performed at the beginning and after 12 mo of freezing. Myopathy linked to freezing showed results of increased meat tenderness, with reduction of crude protein and mineral matter and increase of moisture, fat, and cholesterol, without affecting the meat's collagen percentages. However, these variations with the onset of myopathy do not compromise the consumption of broiled chicken breast meat, kept frozen for up to 12 mo.

ABSTRACT: In modern fast-growing broiler chickens, meat quality becomes increasingly important due to the occurrence of novel breast myopathies such as white striping (WS), woody breast (WB), and spaghetti meat (SM), compromising the sustainability of the poultry industry. Therefore, strategies for reducing the incidence of those myopathies are needed. This study focuses on the impact of different standard ileal digestible (SID) His:Lys ratios on growth performance, meat quality variables like pH, drip loss and pale-soft-exudative (PSE) meat as well as the incidence and severity of breast myopathies (WS, WB, SM), including deep pectoral myopathies (DPM). Thus, 440 male Ross 308 chickens were divided into 5 treatment groups with SID His:Lys ratios of 0.41, 0.45, 0.49, 0.53, and 0.57 in the feed, respectively. Performance was assessed on d 1, 10, 20, 33, and 38 of life. From each treatment group, 22 representative birds were slaughtered on d 38, 39, 40, and 41, respectively. All right fillets were examined 24 h after slaughter by 6 trained testers to assess the outcome of breast myopathies (3-point scale) and PSE-meat (presence and absence). Fillet weight, pH, and drip loss were recorded for selected fillets at different time points. The results of this trial showed no influence of the SID His:Lys ratios on growth performance or drip loss, whereas pH was slightly affected. The study showed a correlation between the occurrence of WB and WS (P < 0.001, normalized contingency coefficient = 0.576). A lower incidence of WB (P = 0.008) was observed in the group fed an SID His:Lys ratio of 0.45 compared with the group fed the lowest ratio of 0.41. For WS, a higher incidence was observed in broilers fed an SID His:Lys ratio of 0.49 (P = 0.002) and 0.53 (P = 0.036) when compared to 0.41. The occurrence of PSE was increased by feeding SID His:Lys at 0.51 (P = 0.008) compared to the lowest ratio. This study showed that the level of His in broiler feed had an impact on the occurrence of breast myopathies, but only WB could be decreased.

An experiment was conducted to validate non-invasive evaluation techniques as in vivo evaluation tools for the myopathies wooden breast and white striping that affect broilers, using biopsy as a support tool. It evaluated 30 Cobb 500® broiler chickens in a completely randomized design consisting of two sexes (males and females) and 15 replications per treatment. At 14, 21, 35, 42 and 49 days, the surface temperature of the birds' breasts was recorded using infrared thermography, analysis of fillet depth, and echogenicity by ultrasound imaging. All broiler chickens were sent for biopsy at 21, 35 and 42 days to collect a fragment of the pectoral muscle for descriptive morphological analyses of histological lesions and muscle fibre morphometry. Males had higher echogenicity values at 14, 21 and 42 days. There was no influence of bird sex on the occurrence of the wooden breast and white striping myopathies at 49 days of age in broilers selected and submitted to the biopsy protocol. There was a general trend of decreasing surface temperature for both sexes according to their age. Muscles with less area occupied with fibres had a lower surface temperature. It was concluded that ultrasonography with a 3.5 MHz transducer detects muscle changes after 28 days of age, which is consistent with the myopathic lesions studied. Infrared thermography is a potential method for detecting changes in breast temperature indicating myopathic lesions. A biopsy can be used as an auxiliary tool in the study of myopathies in broiler chicken breasts. RESEARCH HIGHLIGHTS Detection of changes in the breast muscle after 28 days of age with ultrasonography. Changes in the surface temperature range of pectoral muscle with infrared thermography. Use of biopsy as a tool for early diagnostic evaluation in broiler myopathies. [ABSTRACT FROM AUTHOR]

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ABSTRACT: This study evaluated the level and length of time of vitamin A supplementation and its effects on carcass and cuts yield, meat quality, and myopathies in 42-day-old broilers. A total of 1,920 birds were divided into 6 groups, and each group received a different level of vitamin A: 0; 6,000; 16,000; 26,000; 36,000 and 46,000 IU/ kg. From d 1 to 21, the treatments were distributed among 16 replicates with 20 birds. From the 22nd d on, 8 repetitions remained with the initial treatment and the others received diets with no vitamin A supplementation. Twelve birds were slaughtered per treatment to evaluate carcass and cuts yield, shear force, cooking loss, water holding capacity, and the presence of substances reactive to thiobarbituric acid. The remaining birds were slaughtered and evaluated in loco for Wooden Breast (WB) and White Striping (WS). Wings weight was affected by vitamin A levels. The duration of the vitamin A supplementation process had effects on the weight of breast, legs with a dorsal portion, and meat color in the yellow intensity (b*). Incidence of WB had higher scores in birds supplemented until 42 d of age. WS showed a quadratic response and a lower response with supplementation of 29,700 IU/ kg. Even for WS, a higher occurrence of the normal score was found in birds supplemented until 21 d of age. Minimal quadratic responses were obtained for normal, moderate, and severe scores, in supplementations of 29,301; 29,959, and 29,827 IU/ kg, respectively. WB had lower occurrence rates in birds supplemented until 21 d of age. Consequently, the severe score was more frequent when supplementation was provided until 42 d of age. The level of vitamin A and the length of time during which this supplementation was provided had influence on cuts yield, meat color and the incidence of WB and WS of the 42-day-old birds.