Dietary guanidinoacetate reduces spaghetti meat myopathy risk in the breast muscle of broiler chickens.

The global demand for white chicken meat along with the increase in the occurrence of growth-related breast muscle myopathies (BMMs) [namely white striping (WS), wooden breast (WB), and spaghetti meat (SM)] highlights the need for solutions that will improve meat quality while maintaining the high productivity of modern broilers. Guanidinoacetate (GAA), a precursor of creatine, is used as a feed additive and has previously shown the potential to affect the quality of breast meat. This study investigated growth performance, meat quality and the risk ratio for the development of BMMs in broilers assigned to two dietary treatments: control (CON) group, fed a commercial basal diet, and supplemented GAA (sGAA) group, receiving the control diet supplemented on top with 0.06% GAA. Growth performance indicators such as BW, daily weight gain, daily feed intake, feed conversion ratio and cumulative feed conversion ratio were recorded on a pen basis. As a trait affecting animal welfare, the occurrence of foot pad dermatitis was also evaluated. At day 43, birds were processed, and breasts were scored for the incidence and severity of BMMs (n = 166 and 165 in CON and sGAA groups, respectively). Quality traits (ultimate pH, colour) and technological properties (i.e., drip and cooking losses, marinade uptake, shear force, and oxidation levels of the lipid and the protein fractions) of breast meat were assessed in both treatments on samples not showing any macroscopic sign of BMMs (n = 20 breast fillets per group). Data of myopathy risk ratio were analysed as the risk for each group to develop WS, WB, and SM myopathies. Our results show that while sGAA and control groups did not differ significantly in growth performance, a remarkably beneficial effect of GAA was observed on the incidence of BMMs with significantly reduced risk of sGAA group to develop SM myopathy. The risk of sGAA group to develop SM was 30% lower compared to CON (P = 0.028). Finally, a significantly lower drip loss was observed in sGAA in comparison with CON (1.78 vs 2.48%, P = 0.020). Together, our results show that the inclusion of 0.06% GAA in feed can improve the water-holding capacity of meat and reduce the risk to develop SM myopathy without compromising the performance of broilers.

A critical review of the mechanisms involved in the occurrence of growth-related abnormalities affecting broiler chicken breast muscles.

In the past decade, the poultry industry has faced the occurrence of growth-related muscular abnormalities that mainly affect, with a high incidence rate, the Pectoralis major of the fast-growing genotypes selected for their production performances (high growth rate and breast yield). These myopathies are termed as White Striping, Wooden Breast, and Spaghetti Meat and exhibit distinctive phenotypes. A spatiotemporal distribution has been demonstrated for these disorders as in the early stage they primarily affect the superficial area in the cranial portion of the muscle and, as the birds grow older, involve the entire tissue. Aside from their distinctive phenotypes, these myopathies share common histological features. Thus, it might be speculated that common causative mechanisms might be responsible for the physiological and structural perturbations in the muscle associated with these conditions and might underpin their occurrence. The present review paper aims to represent a critical survey of the outcomes of all the histologic and ultrastructural observations carried out on White Striping, Wooden Breast, and Spaghetti Meat affected muscles. Our analysis has been performed by combining these outcomes with the findings of the genetic studies, trying to identify possible initial causative mechanisms triggering the onset and the time-series of the events ultimately resulting in the development and progression of the growth-related myopathies currently affecting broilers Pectoralis major muscles. Several evidences support the hypothesis that sarcoplasmic reticulum stress, primarily induced an accumulation of misfolded proteins (but also driven by other factors including altered calcium homeostasis and accumulation of fatty acids), may be responsible for the onset of these growth-related myopathies in broilers. At the same time, the development of hypoxic conditions, as a direct consequence of an inadequate vascularization, triggers a time-series sequence of events (i.e., phlebitis, oxidative stress, etc.) resulting in the activation of response mechanisms (i.e., modifications in the energetic metabolism, inflammation, degeneration, and regeneration) which are all strictly related to the progression of these myopathic disorders.

Effect of broiler breast abnormality and freezing on meat quality and metabolites assessed by 1H-NMR spectroscopy.

The present study aimed at investigating the impact of the current growth-related abnormalities (White-Striping-WS, Wooden Breast-WB, and Spaghetti Meat-SM) affecting broilers Pectoralis major muscles on the main quality traits, the oxidative stability of both the lipid and protein fraction as well as the water mobility assessed in fresh and frozen/thawed meat. In addition, Nuclear Magnetic Resonance spectroscopy (1H-NMR) was applied to quantify free amino acids, histidine-containing dipeptides and metabolites involved in energy-generating pathways. Overall, the occurrence of WS, WB, and SM abnormalities remarkably affected the quality traits (pH, color, and water holding capacity) and oxidative stability of the meat, with the WB condition leading to the most detrimental effects. However, overall, freezing and subsequent thawing only partially worsened the aforementioned traits. Significant variations in free amino acids and histidine-containing dipeptides were found between abnormal muscles and their unaffected counterpart by 1H-NMR spectroscopy and, aside from the occurrence of muscular defects, their content was remarkably reduced in frozen/thawed meat. The findings obtained by analyzing the metabolites through 1H-NMR spectroscopy allowed to advance the knowledge concerning the impact of freezing and subsequent thawing on meat quality traits and provided useful information concerning the underlying mechanisms responsible for the development of WS, WB, and SM abnormalities in broilers.

Gaping of pectoralis minor muscles: magnitude and characterization of an emerging quality issue in broilers.

Recently, a certain number of broiler abattoirs located in different Countries around the World have signaled an emerging quality issue termed "gaping" because of the separation of the fiber bundles affecting the external portion of the bipinnate pectoralis minor muscle. Thus, after defining the criteria to classify the muscles as Normal (NORM), Moderate (MOD), or Severe (SEV) cases, the incidence of gaping under commercial conditions was assessed on a total of 8,600 P. minor obtained from broiler chickens belonging to 43 flocks during a 6-mo period. Then, a total of 180 P. minor were selected based on previously defined criteria to evaluate the main quality traits (pH, color, water-holding/-binding capacity and tenderness), proximate composition, water mobility, and thermal properties as well as metabolic profile through 1H-Nuclear Magnetic Resonance spectroscopy. The average incidence of gaping defect was found to be 16.8% (8.8 and 8.0% MOD and SEV cases, respectively). As for the main quality traits, a reduction in ultimate pH was observed as the severity of the gaping defect increased, with SEV muscles displaying significantly lower values in comparison with NORM (5.96 vs. 6.02; P < 0.01), while MOD showed intermediate values (5.99). Concurrently, if compared with their NORM counterpart, MOD and SEV exhibited higher lightness (53.6 and 54.2 vs. 51.8; P < 0.01) coupled with higher (P < 0.05) cooking losses and longer (P < 0.05) transversal relaxation time of extra-myofibrillar water fraction. Overall, no significant differences were found concerning proximate composition and thermal properties. With regard to the metabolic profile, a significantly lower (P < 0.001) glutamine concentration was found in MOD and SEV muscles that, concurrently, revealed significant (P < 0.05) variations in the metabolites involved in energy-generating pathways. Overall, these findings evidenced that the gaping defect affecting broilers' P. minor muscles have strong similarities with the pale-soft-exudative condition previously described in poultry and likely results from the biochemical processes taking place during the post-mortem conversion of muscle to meat.

Comparison of 2 commercial turkey hybrids: productivity, occurrence of breast myopathies, and meat quality properties.

This study was undertaken to compare productive performance, occurrence of breast myopathies, chemical composition, and technological properties of the meat in 2 dominant commercial turkey hybrids. A total of 972 1-day-old male turkey poults (equally divided in hybrid A and B) were randomly distributed in 18 floor pens. Overall, productive performance resulted similar between the genotypes, although they showed different growth profile (turkeys from group B grew up faster up to 84 d). Regarding the occurrence of myopathies, the percentage of breasts affected by white striping was markedly higher in both genotypes (46 vs. 60% of severe lesions, respectively for A and B; P < 0.05), while the occurrence of spaghetti meat-like condition was negligible. The histological features of the different categories of meat abnormalities resulted similar to those previously described for chicken hybrids. The technological traits such as ultimate pH, lightness, redness, marinade uptake, cooking losses, and shear force were not significantly affected by the genotype. However, turkeys from group B exhibited lower yellowness (b*, 0.50 vs. 1.04; P < 0.05) and higher drip losses (1.34 vs. 1.26%; P < 0.05). The shelf-life test on thigh meat showed no significant changes in meat color over the storage time in both hybrids, whereas thigh meat from group A showed absolute lower values of lightness (L*) and yellowness (b*) (P < 0.05). Lipid oxidation of thigh meat significantly increased during storage, although no significant difference was found between the hybrids. Proximate composition and intramuscular collagen properties resulted similar between genetic lines with the exception of total fat content (1.55 vs. 1.21%, respectively for A and B; P < 0.05). The genotype had a moderate effect on fatty acid families of breast meat as only monounsaturated fatty acid content was significantly affected (31.7 vs. 29.8%, respectively for A and B). In conclusion, the overall productive traits of commercial turkeys, including the occurrence of muscle myopathies, as well as quality attributes of fresh and refrigerated meat were only slightly affected by the genotype.

Effect of different arginine-to-lysine ratios in broiler chicken diets on the occurrence of breast myopathies and meat quality attributes.

This study was carried out to evaluate the effect of different digestible arginine-to-lysine (dig Arg:Lys) ratio in broiler diets on the occurrence of breast myopathies, productivity, and meat quality traits. A total of 1,755 1-day-old Ross 308 male chicks was randomly divided in 3 experimental groups (9 replications/group): CON, fed a 4 feeding-phases commercial diet (dig Arg:Lys ratio = 1.05, 1.05, 1.06, 1.07, respectively in starter, grower I, grower II and finisher phase), and ARG2 and ARG3 groups fed CON diet supplemented respectively with 20 and 30% higher levels of crystalline L-arginine (dig Arg:Lys ratio = 1.25, 1.25, 1.26, 1.27 and 1.35, 1.35, 1.36, 1.37, respectively). Productive performance was recorded throughout the rearing cycle. At processing (43 d), breasts (n = 150/group) were randomly collected to evaluate the incidence and severity of white striping (WS), wooden breast (WB), and spaghetti meat (SM) defects (3-points scale). Meat quality traits, such as color, pH, drip and cook losses, marinade performances, and proximate composition were determined on 12 fillets/group. Although productive performance and meat quality traits resulted not significantly affected, the occurrence of some breast myopathies was modified by the dietary treatments. ARG2 and ARG3 exhibited a significantly higher percentage of breast without WS compared to CON (28 and 41 vs. 17%, respectively; P < 0.001). ARG3 reported the lowest percentage of breasts with severe WS (11 vs. 27 and 31%, respectively for ARG3, ARG2, and CON; P < 0.001) and the highest of those showing no SM abnormality (81 vs. 69 and 65%, respectively for ARG3, ARG2, and CON; P < 0.01). Furthermore, a numerical reduction of breasts with severe WB was observed in ARG3 (12 vs. 25 and 19%, respectively for ARG3, ARG2, and CON; P = 0.12). In conclusion, the dietary supplementation of arginine to increase the dig Arg:Lys ratio by about 30% in respect to the current recommendations for broiler chickens has positive implications on the occurrence of some breast meat abnormalities.

Wooden-Breast, White Striping, and Spaghetti Meat: Causes, Consequences and Consumer Perception of Emerging Broiler Meat Abnormalities.

Ten years ago, the occurrence of macroscopic defects in breasts muscles from fast-growing broilers challenged producers and animal scientists to label and characterize myopathies wholly unknown. The distinctive white striations in breasts affected by white striping disorder, the presence of out-bulging and pale areas of hardened consistency in the so-called wooden breast, and the separation of the fiber bundles in breasts labelled as spaghetti meat, made these myopathies easily identified in chicken carcasses. Yet, the high incidence of these myopathies and the increasing concern by producers and retailers led to an unprecedented flood of questions on the causes and consequences of these abnormal chicken breasts. This review comprehensively collects the most relevant information from studies aimed to understand the pathological mechanisms of these myopathies, their physicochemical and histological characterization and their impact on meat quality and consumer's preferences. Today, it is known that the occurrence is linked to fast-growth rates of the birds and their large breast muscles. The muscle hypertrophy along with an unbalanced growth of supportive connective tissue leads to a compromised blood supply and hypoxia. The occurrence of oxidative stress and mitochondrial dysfunction leads to lipidosis, fibrosis, and overall myodegeneration. Along with the altered appearance, breast muscles affected by the myopathies display poor technological properties, impaired texture properties, and reduced nutritional value. As consumer's awareness on the occurrence of these abnormalities and the concerns on animal welfare arise, efforts are made to inhibit the onset of the myopathies or alleviate the severity of the symptoms. The lack of fully effective dietary strategies leads scientists to propose whether "slow" production systems may alternatively provide with poultry meat free of these myopathies.

Effect of white striping on turkey breast meat quality.

In the past decades, the intense selection practices carried out in order to develop fast growing and high breast-yield turkey hybrids profoundly modified the muscle physiology leading to the development of growth-related alterations and muscular abnormalities. White striations of variable thickness have been particularly observed on the ventral surface of Pectoralis major muscle belonging from heavy male turkeys since several years. However, although the effects of white striping (WS) have been extensively studied on broilers, this condition was not considered as a main quality issue by both turkey producers and meat industry. Thus, this study aimed at evaluating whether the occurrence of WS in heavy male turkeys affects the quality traits and technological properties of meat to the same extent previously observed for broilers. In two replications, 72 Pectoralis major muscles were classified as: normal (NORM), moderate WS (MOD) and severe WS (SEV) cases. The whole muscle was weighed and cut in order to assess colour, ultimate pH, water holding (drip and cooking losses) and binding (marinade uptake) capacities, NMR relaxation properties, shear force as well as proximate composition of meat. The Pectoralis major muscles affected by WS (both moderate and severe cases) exhibited a one-fifth increased weight in comparison with their NORM counterpart. However, the occurrence of WS only partially affected the proximate composition of the meat. In detail, although moisture, collagen and protein contents did not differ among the groups, if compared with NORM, higher lipid levels were found in SEV muscles, whereas MOD had intermediate values. On the other hand, both MOD and SEV exhibited lower ash content. Despite these variations in proximate composition, both water holding and binding capacities of turkey breast meat were not affected by WS. Indeed, quality traits of raw (pH, colour, cooking losses and shear force) and marinated (uptake, cooking losses and shear force) meat as well as water distribution within the muscle tissue did not differ between NORM and WS cases. Overall, if compared with broilers, WS only marginally affected quality traits of turkey breast meat. It might thus be hypothesised a diverse specie-specific physiological response to the pressure in muscle tissue induced by the selection in turkeys that, although analogously led to the occurrence of WS, results in limited effects on meat quality.

Evolution of proteolytic indicators during storage of broiler wooden breast meat.

In the past few yr, an emerging muscle abnormality termed wooden breast (WB) was found to affect broilers' Pectoralis major muscles. Although different studies have been performed in order to evaluate the effect of WB on meat quality, there is no evidence concerning its impact on the proteolytic processes taking place during meat aging. Thus, this study aimed at investigating the effect of a 7-day storage of broiler breast fillets on free calcium concentration, calpain activity, and proteolysis. Both the superficial and the deep layers of the Pectoralis major muscles were considered. Although similar electrophoretic profiles were observed by comparing the corresponding sampling positions, an evident lack of a high-molecular weight protein band, ascribed to nebulin, was found in the superficial layer of the WB fillets at 10 h postmortem. Compared to normal fillets (NB), both the superficial and the deep layer of WB exhibited a significantly higher amount of free calcium at 168 h postmortem (96 and 88 vs. 20 and 53 µM; P ≤ 0.001). Casein zymograms evidenced the presence of µ/m-calpain and its autolyzed form migrating as a doublet within the gel. Interestingly, neither the occurrence of WB nor the intra-fillet sampling position exerted any relevant effect on calpain activity. Indeed, a significant reduction (P ≤ 0.05) in the unautolyzed µ/m-calpain activity coupled with a remarkable increase (P ≤ 0.05) in the autolyzed form activity was observed during storage. Concurrently, if compared to NB, a significantly larger (P ≤ 0.05) amount of desmin was detected in both the superficial and the deep layers of the WB samples at 10 h postmortem. Then, a sharp decrease of the intact desmin band coupled with a progressive accumulation of its 39-kDa degradation fragment was observed without any significant difference among groups. In conclusion, the increased hardness that typically affects the WB cases seemed not to be exclusively attributable to differences in the proteolytic processes taking place within the postmortem period.

Implications of white striping and spaghetti meat abnormalities on meat quality and histological features in broilers.

During the past few years, there has been an increasing prevalence of broiler breast muscle abnormalities, such as white striping (WS) and wooden breast conditions. More recently, a new muscular abnormality termed as spaghetti meat (SM) because of the altered structural integrity of the Pectoralis major muscle often associated with WS has emerged. Thus, this study aimed at evaluating the effects of WS and SM conditions, occurring alone or combined within the same P. major muscle, on meat quality traits and muscle histology. In two replications, 96 P. major muscles were classified into four classes: normal (N), WS, SM and WS/SM. The whole fillet was used for weight assessment and morphometric measurements, then each sample was cut in order to separate the superficial layer from the deep one and used to evaluate proximate composition, histological features, nuclear magnetic resonance relaxation times, functional properties and both myofibrillar and sarcoplasmic proteins profile. Fillets affected by WS and SM abnormalities exhibited higher weights and increased thickness and length. SM condition was associated with a relevant decrease in protein content coupled with a significant increase in moisture level, whereas fat content was affected only by the simultaneous presence of WS. Histological evaluations revealed that abnormal samples were characterized by several degenerative aspects that almost completely concerned the superficial layer of the fillets. White striped fillets exhibited necrosis and lysis of fibers, fibrosis, lipidosis, loss of cross striation and vacuolar degeneration. Moreover, SM samples were characterized by poor fiber uniformity and a progressive rarefaction of the endo- and peri-mysial connective tissue, whereas WS/SM fillets showed intermediate histological features. Nuclear magnetic resonance relaxation analysis revealed a higher proportion of extra-myofibrillar water in the superficial section of all the abnormal fillets, especially in SM samples, which consequently led to a reduction of the water holding capacity of meat. As for functional properties, abnormal fillets exhibited a lower protein solubility and higher ultimate pH values on both the superficial and deep sections. Although abnormal fillets exhibited higher yellowness values, no relevant effect on meat color was observed. The occurrence of WS and SM abnormalities led to increased carbonylation levels and more intense proteolytic processes. Overall, muscle abnormalities mainly affect the superficial layer of P. major muscle and particularly the occurrence of SM myopathy seems to implicate a more pronounced modification of meat quality traits than the mere presence of WS.

Histology, composition, and quality traits of chicken Pectoralis major muscle affected by wooden breast abnormality.

Only a few years ago, the poultry industry began to face a recent abnormality in breast meat, known as wooden breast, which frequently overlaps with white striping. This study aimed to assess the impact of wooden breast abnormality on quality traits of meat. For this purpose, 32 normal (NRM), 32 wooden (WB), and 32 wooden and white-striped (WB/WS) Pectoralis major muscles were selected from the same flock of heavy broilers (males, Ross 708, weighing around 3.7 kg) in the deboning area of a commercial processing plant at 3 h postmortem and used to assess histology, proximate (moisture, protein, fat, ash, and collagen) and mineral composition (Mg, K, P, Na and Ca), sarcoplasmic and myofibrillar protein patterns, and technological traits of breast meat. Compared to the normal group, WB/WS fillets showed more severe histological lesions characterized by fiber degeneration, fibrosis, and lipidosis, coupled with a significantly harder texture. With regard to proximate and mineral composition, abnormal samples exhibited significantly (P < 0.001) higher moisture, fat, and collagen contents coupled with lower (P < 0.001) amounts of protein and ash. Furthermore, increased calcium (131 vs. 84 mg kg(-1); P < 0.05) and sodium (741 vs. 393 mg kg(-1); P < 0.001) levels were found in WB/WS meat samples. The SDS-PAGE analysis revealed a significantly lower amount of calcium-ATPase (SERCA, 114 kDa), responsible for the translocation of Ca ions across the membrane, in normal breasts compared to abnormal ones. As for meat quality traits, fillets affected by wooden abnormality exhibited significantly (P < 0.001) higher ultimate pH and lower water-holding/water-binding capacity. In particular, compared to normal, abnormal samples showed reduced marinade uptake coupled with increased drip loss and cooking losses as well. In conclusion, this study revealed that meat affected by wooden breast or both wooden breast and white striping abnormalities exhibit poorer nutritional value, harder texture, and impaired water-holding capacity.

Implications of white striping and wooden breast abnormalities on quality traits of raw and marinated chicken meat.

One of the consequences of intense genetic selection for growth of poultry is the recent appearance of abnormalities in chicken breast muscles, such as white striping (characterised by superficial white striations) and wooden breast (characterised by pale and bulged areas with substantial hardness). The aim of this study was to evaluate the quality traits of chicken fillets affected by white striping and wooden breast abnormalities. In two replications, 192 fillets were divided into the following four classes: normal (n=48; absence of any visual defects), white striping (n=48, presence of white striations), wooden breast (n=48; diffusely presence of hardened areas) and white striping/wooden breast (n=48; fillets affected by both abnormalities). Morphology, raw meat texture and technological properties were assessed in both unprocessed (pH, colour, drip loss, cooking loss and cooked meat shear force) and marinated meat (marinade uptake, purge loss, cooking loss and cooked meat shear force). Fillets affected by white striping, wooden breast or both abnormalities exhibited higher breast weights compared with normal fillets (305.5, 298.7, 318.3 and 244.7 g, respectively; P<0.001). Wooden breast, either alone or in combination with white striping, was associated with a significant (P<0.001) increase of fillet thickness in the caudal area and raw meat hardness compared with both normal and the white striping abnormality, for which there was no difference. Overall, the occurrence of the individual and combined white striping and wooden breast abnormalities resulted in substantial reduction in the quality of breast meat, although these abnormalities are associated with distinct characteristics. Wooden breast fillets showed lower marinade uptake and higher cooking losses than white-striped fillets for both unprocessed and marinated meats. On the other hand, white-striped fillets showed a moderate decline in marinade and cooking yield. Fillets affected by both abnormalities had the highest (P<0.001) ultimate pH values. In contrast, the effects on colour of raw and cooked meat, drip loss, purge loss and cooked meat shear force were negligible or relatively low and of little practical importance. Thus, the presence of white striping and wooden breast abnormalities impair not only breast meat appearance but also the quality of both raw and marinated meats mainly by reducing water holding/binding abilities.

Malignant ectomesenchymoma. Case report and review of the literature.

Malignant ectomesenchymoma is an uncommon neoplasm composed of neuroectodermal elements and one or more mesenchymal neoplastic elements. It is believed to arise from remnants of migratory neural crest cells (ectomesenchyme). The authors report the clinical and pathological findings of a 3-year-old girl with malignant ectomesenchymoma of the CNS. Embryogenesis of this tumor is discussed, and a review of the literature with 39 other cases is done.