**2. Economic impact and losses for the poultry industry**

A variable portion of chicken breasts affected by the aforementioned myopathies were reported by [1] and may be due to: This author lists in the following sequence, factors that are a consequence of myopathies, being: (a) condemnation/ cut (whole breast, carcass); (b) lower yield and value since there will be changes in the water retention capacity [WHC], emulsification and gelation capacity; (c) manual separation in the deboning line to be intensified (addition and training of personnel for classification/sorting - highest cost); and (d) there will be rejection from consumers, since undesirable sensory changes occur in this meat". Consequently, all these factors are responsible for economic loss in the poultry sector.

As there are different forms of myopathies already cataloged, if all of them manifested together, certainly a refrigerator could lose millions in a few hours of slaughter, taking into account that there are systems that work with 350.00 heads of birds slaughtered in a 12-hour period (personal note author). Knowing this, several studies were carried out to try to quantify the percentage and some of the dollar values of the damage that WB and WS can generate.

In a study carried out in the United States, it was reported that more than 50% of the studied squad developed WB [18]. Additionally, study with growing birds on farms under commercial conditions observed that 96.1% developed WB [19]. In 2017, in Italy, [20] observed 474 carcasses and of these, 53.2% developed WB. Regarding values, there are two articles regarding this survey, with Kuttappan et al. [16] indicating annual economic losses for the American market in the range of \$ 200 million. For the Brazilian market, there are estimated values of

*Advances in Poultry Nutrition Research*

conditions and not from inflammation process.

to Ordinance No

the training mechanisms.

as "chest file" ceases or "sassami") with degeneration, necrosis and atrophy. In reference [8] reported that this anomaly can also be caused when blood circulation ceases due to intense muscle exercise, with voluntary movement of the wings where the muscle is unable to expand and ischemic necrosis of the chest muscle occurs.

only when the carcass follows a more detailed evaluation at the Department of Final Inspection (DIF) or in the boning room [9]. However, in a review published by [6] that mentions research by Pereira et al. [10] found that myopathy can be a technopathy caused by changes in technology and, if possible, adapt the pre-slaughter management to reduce the damage caused, and these can be consumed, because it is not an issue food security, but rather a product quality problem. Reference [11] pointed out that the green color probably came from the transformation of myoglobin in anaerobic

Others anomalies in the chest and small chest file have caused damage to the refrigerators. In [12] observed in Finland that there was an increase in chicken breasts with abnormalities that was characterized in the pectoralis major muscle, with pale and hard external areas with white streaks, in which they caused rejection by the consumer and, consequently, there were economic losses in industries. They did not find a relationship between these anomalies and any antemortem symptoms. Through electron microscopy analysis, this type of anomaly was called WS (**Figure 2**). Still, concerning anomalies, another occurrence in chicken breasts was investigated by [13] and called WB, however, the breast had a yellowish color and a certain hardness accompanied by inflammatory processes and necrosis. Both anomalies had similar histological characteristics. However, there is no information about the implication of these anomalies in the quality of the products, as well as

White streaks of chicken breast called WS (**Figure 2**), according to [8] are related to adipose tissue according to histological and chemical analyzes. While the characteristics of chicken breast with WB are related to the connective tissue that was characterized by muscle hardening [12]. Thus, these two myopathies highlighted in the present proposal, present specific differences, being that WS was characterized by the development of white fibers of the connective tissue and that

*Breast fillets displaying different degrees of white striping. Score 0 indicates no white striping and score 3* 

Therefore, during the deboning process, this muscle is condemned, however, when there is production of whole chicken, it is not possible to identify it, because according

. 210, of November 10, 1998, the supra-coracoid muscle is exposed

**176**

**Figure 2.**

*indicates severe white striping [8].*

\$ 70,632.00 thousand/day, this being the only work that associated WB with WS to calculate economic losses [21].

The data provided above are reported by different authors, however, the group responsible for preparing this review has worked directly with slaughterhouses in the Southern Region of Brazil and some data are being obtained gradually. Data collected during 30 days of slaughter monitoring during the year 2020 raised the following numbers: of the total and partial convictions of the carcasses as a consequence of dermatoses, myopathies, arthritis, contusion/fracture and contamination, a loss of around \$ 162,926.49 occurs a total of 2 million birds slaughtered. This value represents about X% of monthly loss for the sector. If there is an extrapolation that these condemnations can be minimized in the same way as WS my WB myopathies and that they can be associated with the same etiologies, that is, with the rapid growth of these animals, and this equation can be adjusted so that the gain of weight is gradually adaptable to the physiology of these birds, these changes could be minimized and the condemnations, in turn, would gradually decrease, which would generate greater revenue for the slaughterhouses.

Given the great economic loss caused by these myopathies, their characterization and understanding concerning their development, changes in meat quality standards, possible changes in carcasses beside the affected muscles and how these occurrences can affect meat processing, whether or not being associated with a loss of welfare of these animals is necessary information for the sector. The compilation of this information, in a systematic way, could minimize the negative impact of these myopathies, resulting in a higher yield for the sector, as well as an improvement in the quality of the final product that will reach the consumer.

#### **3. Proteins and connective tissue**

Protein material is a determinant when it comes to meat. In reference [6] comments that the muscular protein organization and nature is important in the way they are metabolically reversed. The skeletal muscle has three proteic classes based on its solubility; the myofibrillar class is the main one and, as myofibrillar proteins are built in a myofibrillar structure in the striated muscle, presenting a challenge for protein turnover. Analyzing these recent advances in the understanding of this protein system, there are indications that myofibrillar proteins are first hydrolyzed before being degraded and reused. It is still not entirely clear how this dissociation occurs, it is suggested that there may be the release of a group of easily hydrolyzable myofilaments, or it may involve the exchange of myofibrillar proteins in the cell's cytoplasm, or both mechanisms may occur at the same time [22].

In addition to the information mentioned above, on quality parameters for chicken meat, it is necessary to target other lines of research that can provide differentiated responses, or that the responses add up to have a system of information that takes the responses that the industry is looking for. Therefore, research on protein turnover in broilers has been carried out for a considerable time, however much is still not known about the subject. Still referring review of [6], the authors report that the protein turnover in laying hens is associated with the differences between sexual maturity, age, stage and feeding posture.

Genetic-based research with genes related to protein degradation (IGF-1, ampk, anthrogin-1, MURF1 and Cathepsin B) is being developed, however, its expression changes due to changes in protein turnover. These genes have already been sequenced for chickens [23–26]. In an article published in 2017, the authors [27] make interesting comments, some of which are briefly as follows: protein synthesis rates are not different for normal meats or WS, however, protein degradation rates

**179**

*White Striping and Wooden Breast Myopathies in the Poultry Industry: An Overview of Changes…*

are different between both; increased expression of the MuRF1 and Anthrogin 1 genes are responsible for the highest rate of protein degradation. Despite these sequences, there is still no understanding for these protein changes in birds. This can theoretically lead to greater protein degradation and consequently high catabolic rates, leading to an imbalance in the body of these birds, resulting in the production of proteins that may be deficient, as in the case of collagen for support-

In addition to the possibilities involving protein turnover, and as this can influence muscle development, there are still other hypotheses that are being raised to better define the process of meat formation with WS and WB anomalies. One of them is associated with the number of mitochondria present in the tissue, indicating the possibility of a low concentration of these organelles in these muscles [28]. This could explain the need for healing processes in these muscles, which are characterized by muscle striation, indicating the need for deposition of connec-

In addition to this information, studies are addressing the welfare of these birds, since compromising the structure of the carcass as a whole, there may be a direct impairment of their mobility. Reference [29] observed a degree of structural abnormality in all samples of chickens with rapid weight gain. However, there are symptoms in birds that do not affect all individuals affected by WB, however, there may be possible links with the environment [16]. It is not known numerically whether WB or WS affects the behavior, the ability to walk or the welfare of these birds. The hypothesis has been raised that these myopathies would harm mobility

If there is bibliographic support concerning the mobility of these animals, consequently, this information can be extrapolated to a probable deficiency in the production of connective tissue, since there must be a deviation of nutrients in the metabolism of these animals, to supply the inflammatory processes. Muscle and joint. According to [30], the main histological lesions of the WB muscle, which consist of chronic myodegeneration with regeneration and interstitial edema, accumulation of loose connective tissue or fibrosis and replacement of severely degenerated muscle fibers with connective tissue with excessive fibrosis.

As the connective tissue is crucial for the development of the entire system, as well as muscles, skin and bones, there is a need for a balanced distribution of nutrients throughout the animal's body. In a study published by [31] there is a report on the difference in the organization of collagen, which may be due to the expression of proteoglycan decorin in the extracellular matrix. Decorina is a regulator of collagen crosslinking and is expressed in levels significantly in strains affected by WB, which would lead to tightly compressed collagen fibers due to the high levels of crosslinking of this protein. Besides, the expression of muscle-specific transcriptional regulatory factors for proliferation and differentiation of muscle cells that lead to muscle regeneration in response to muscle damage was significantly elevated for these myopathies. The lack of decorin has been mapped as a destabilizer of the collagen structure due to abnormal collagen crosslinking, leading to fragility of the

The information mentioned above in this brief literature review shows an overview of the problem, however, through reports from slaughterhouses, in the day-to-day work of the Research Group that is developing this proposal, there is evidence that the animals that develop WS or WB are more likely to have problems associated with the quality of their skin. It has been observed in the field and in

and, therefore, have welfare implications for animals.

skin, caused by an abnormal fibrillar network [32].

**3.1 Collagen, bone tissue and fractures**

*DOI: http://dx.doi.org/10.5772/intechopen.96513*

ing the skin.

tive tissue.

#### *White Striping and Wooden Breast Myopathies in the Poultry Industry: An Overview of Changes… DOI: http://dx.doi.org/10.5772/intechopen.96513*

are different between both; increased expression of the MuRF1 and Anthrogin 1 genes are responsible for the highest rate of protein degradation. Despite these sequences, there is still no understanding for these protein changes in birds. This can theoretically lead to greater protein degradation and consequently high catabolic rates, leading to an imbalance in the body of these birds, resulting in the production of proteins that may be deficient, as in the case of collagen for supporting the skin.

In addition to the possibilities involving protein turnover, and as this can influence muscle development, there are still other hypotheses that are being raised to better define the process of meat formation with WS and WB anomalies. One of them is associated with the number of mitochondria present in the tissue, indicating the possibility of a low concentration of these organelles in these muscles [28]. This could explain the need for healing processes in these muscles, which are characterized by muscle striation, indicating the need for deposition of connective tissue.

In addition to this information, studies are addressing the welfare of these birds, since compromising the structure of the carcass as a whole, there may be a direct impairment of their mobility. Reference [29] observed a degree of structural abnormality in all samples of chickens with rapid weight gain. However, there are symptoms in birds that do not affect all individuals affected by WB, however, there may be possible links with the environment [16]. It is not known numerically whether WB or WS affects the behavior, the ability to walk or the welfare of these birds. The hypothesis has been raised that these myopathies would harm mobility and, therefore, have welfare implications for animals.

If there is bibliographic support concerning the mobility of these animals, consequently, this information can be extrapolated to a probable deficiency in the production of connective tissue, since there must be a deviation of nutrients in the metabolism of these animals, to supply the inflammatory processes. Muscle and joint. According to [30], the main histological lesions of the WB muscle, which consist of chronic myodegeneration with regeneration and interstitial edema, accumulation of loose connective tissue or fibrosis and replacement of severely degenerated muscle fibers with connective tissue with excessive fibrosis.

As the connective tissue is crucial for the development of the entire system, as well as muscles, skin and bones, there is a need for a balanced distribution of nutrients throughout the animal's body. In a study published by [31] there is a report on the difference in the organization of collagen, which may be due to the expression of proteoglycan decorin in the extracellular matrix. Decorina is a regulator of collagen crosslinking and is expressed in levels significantly in strains affected by WB, which would lead to tightly compressed collagen fibers due to the high levels of crosslinking of this protein. Besides, the expression of muscle-specific transcriptional regulatory factors for proliferation and differentiation of muscle cells that lead to muscle regeneration in response to muscle damage was significantly elevated for these myopathies. The lack of decorin has been mapped as a destabilizer of the collagen structure due to abnormal collagen crosslinking, leading to fragility of the skin, caused by an abnormal fibrillar network [32].

#### **3.1 Collagen, bone tissue and fractures**

The information mentioned above in this brief literature review shows an overview of the problem, however, through reports from slaughterhouses, in the day-to-day work of the Research Group that is developing this proposal, there is evidence that the animals that develop WS or WB are more likely to have problems associated with the quality of their skin. It has been observed in the field and in

*Advances in Poultry Nutrition Research*

calculate economic losses [21].

would generate greater revenue for the slaughterhouses.

**3. Proteins and connective tissue**

ment in the quality of the final product that will reach the consumer.

cytoplasm, or both mechanisms may occur at the same time [22].

between sexual maturity, age, stage and feeding posture.

\$ 70,632.00 thousand/day, this being the only work that associated WB with WS to

The data provided above are reported by different authors, however, the group responsible for preparing this review has worked directly with slaughterhouses in the Southern Region of Brazil and some data are being obtained gradually. Data collected during 30 days of slaughter monitoring during the year 2020 raised the following numbers: of the total and partial convictions of the carcasses as a consequence of dermatoses, myopathies, arthritis, contusion/fracture and contamination, a loss of around \$ 162,926.49 occurs a total of 2 million birds slaughtered. This value represents about X% of monthly loss for the sector. If there is an extrapolation that these condemnations can be minimized in the same way as WS my WB myopathies and that they can be associated with the same etiologies, that is, with the rapid growth of these animals, and this equation can be adjusted so that the gain of weight is gradually adaptable to the physiology of these birds, these changes could be minimized and the condemnations, in turn, would gradually decrease, which

Given the great economic loss caused by these myopathies, their characterization and understanding concerning their development, changes in meat quality standards, possible changes in carcasses beside the affected muscles and how these occurrences can affect meat processing, whether or not being associated with a loss of welfare of these animals is necessary information for the sector. The compilation of this information, in a systematic way, could minimize the negative impact of these myopathies, resulting in a higher yield for the sector, as well as an improve-

Protein material is a determinant when it comes to meat. In reference [6] comments that the muscular protein organization and nature is important in the way they are metabolically reversed. The skeletal muscle has three proteic classes based on its solubility; the myofibrillar class is the main one and, as myofibrillar proteins are built in a myofibrillar structure in the striated muscle, presenting a challenge for protein turnover. Analyzing these recent advances in the understanding of this protein system, there are indications that myofibrillar proteins are first hydrolyzed before being degraded and reused. It is still not entirely clear how this dissociation occurs, it is suggested that there may be the release of a group of easily hydrolyzable myofilaments, or it may involve the exchange of myofibrillar proteins in the cell's

In addition to the information mentioned above, on quality parameters for chicken meat, it is necessary to target other lines of research that can provide differentiated responses, or that the responses add up to have a system of information that takes the responses that the industry is looking for. Therefore, research on protein turnover in broilers has been carried out for a considerable time, however much is still not known about the subject. Still referring review of [6], the authors report that the protein turnover in laying hens is associated with the differences

Genetic-based research with genes related to protein degradation (IGF-1, ampk,

anthrogin-1, MURF1 and Cathepsin B) is being developed, however, its expression changes due to changes in protein turnover. These genes have already been sequenced for chickens [23–26]. In an article published in 2017, the authors [27] make interesting comments, some of which are briefly as follows: protein synthesis rates are not different for normal meats or WS, however, protein degradation rates

**178**

the slaughter plants that these animals have the most fragile skin, with lesions that occur both within the farms and during the plucking process, there may be a greater correlation of bone fractures with these anomalies and consequently a considerable economic loss for the sector, since the carcasses may have partial or total condemnation.

Research developed by [33] related WB myopathy with problems associated with the formation of bone tissue. These authors evolve an interesting line of reasoning based on the development of bone marrow-forming cells and how the increase in adipocytes can influence this process. As a result, they obtained positive correlations, and the levels of calcium and phosphorus in the bone matrix of animals that develop WB are lower when compared to those not affected by myopathy.

A study by [34] that analyzed the efficiency of magnesium in the control of oxidative processes in birds, as well as its correlation with the decreased incidence of development of WS and WB myopathies, concluded that magnesia supplementation protected the tissue against protein oxidation and that it reduced the incidence of WS and WB myopathies to almost half the occurrence in fed animals supplemented with this mineral. In the same study, these authors report that even Calcio and Magnesium use unusual mechanisms of divalent ions for their absorption, one does not harm the absorption of the other, and the same occurred for Phosphorus. The results were innovative since magnesium did not interfere with the action of other minerals, a positive factor, since this benefits the bone matrix, so supplementation with magnesium in the feed of broilers can be a promising alternative as a supplement to mitigate the development of WS and WB myopathies.

## **4. Microbiota**

Another parallel approach to be considered is the intestinal microbiota of birds, as this is an innovative aspect of the proposal since recent studies have verified the importance of the intestinal microbiota in animal performance, health and wellbeing [35–37]. There is still a close relationship between the diet, microbiota and bioactive compounds that may be present or that are used commercially in poultry feed. Studies that address the interaction of the microbiota are still limited and are at the frontier of knowledge under the paradigm of sustainable poultry production, prioritizing animal welfare.

The microbiota is recognized as the "fifth organ" and the literature suggests that the microbiome plays a crucial role in signal processing and interaction with the environment [38]. The composition of the bacterial microbiota is affected by the bacteria present in the intestine and by the natural microorganisms in the environment [39]. Chicks born in natural conditions receive the microbiota from adults, mainly from the mother. Industrial poultry farming has altered this condition, preventing the chick from coming into contact with the mother, which leads to a delay in the development of the protective intestinal microbiota [40, 41]. The balance of the microbiota can be affected by several factors, both endogenous and exogenous. Poor hygienic-sanitary conditions, stress, food, intoxication and illness, can trigger the increase in bacterial proliferation that can compete for nutrients. They can also determine inflammatory processes, which leads to thickening of the intestinal wall, which will reduce absorption, increase the excretion of metabolites and toxins that trigger enteritis and decrease the transit time of the digesta. Besides, it can increase the turnover of epithelial cells, which allow bacterial and endotoxin translocation to other organs, leading to septicemia [42]. According to [43] it is important to understand and have control over the possible changes in the intestinal microbiota to adapt the management and to include in a rational way additives that

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*White Striping and Wooden Breast Myopathies in the Poultry Industry: An Overview of Changes…*

can alter and regulate the microbial ecology, to improve zootechnical performance

In adult birds, when the microbiota is established, it may contain 400 to 500 microbial species [44]. With variations in the amount and types of microorganisms that may be attached to the epithelium or free in the lumen. When free, they may have an accelerated multiplicative capacity, minimizing loss through peristalsis, and may be associated with other bacteria that are linked to the mucosa. These variations mean that, in general, the small intestine is colonized by facultative microaerophilic bacteria, with their respective representation (in percentage) in the microbiota, which is: *Lactobacillus* (70%), *Clostridiaceae* (11%), *Streptococcus* (6.5%), *Enterococcus* (6.5%). The cecum, on the other hand, has mandatory anaerobic bacteria such as *Clostridiaceae* (65%), *Fusobacterium* (14%), *Bacteroides* (5%), and is also permeated by facultative microaerophilic bacteria such as *Lactobacillus*

A study by [47] who investigated the microbiota of WB and normal birds to understand the differential expression of plasma metabolites, obtained different results between groups, with non-myopathic broilers produced more heat, with higher body protein content, validated by the higher protein: fat ratio. Lower protein content in myopathic birds was verified, due to the probable high myiodegeneration, as observed by the high expression of 3-methylhistidine in plasma. In this work, the authors also reported that there was a predominance of unclassified Lactobacillus in birds with myopathy; while the species, L. acidipiscis was the predominant bacterium for non-myopathic broilers. The differentially significant metabolites identified in the plasma metabolome between the two groups were homocysteine, cyclic GMP, trimethylamine N-oxide, tyramine, carnitine and acetylcarnitine, all associated with the cardiovascular system. The results of this work suggest that more research on broilers should be carried out with a focus on

As WS and WB are proven to be inflammatory processes that permeate the entire carcass, it is possible to raise the hypothesis that alteration in the microbiota may be determinant for birds to be predisposed to develop these anomalies, consequently, there may be changes in the absorption of limiting amino acids or even essential for the synthesis of important proteins such as collagen and other proteins that can

**5. Animal welfare: possible changes due to the occurrence of wooden** 

Brazil occupies 1st place, exporting approximately 4.3 million tons [48].

Brazilian poultry stands out in the international meat market, and according to data from the Brazilian Association of Animal Protein (ABPA 2018), Brazil was in 2nd place in the world production of chicken meat (2017) with 13.05 million tons, second only to the United States, which produced 18.6 million tons. As for exports,

Poultry intended for meat production must be assisted to comply with specific conformities for farms, such as maximum animal density, minimum lighting intensity, air quality, water and food availability, among others. Also, meat mortality and inspection data are considered to establish maximum values of stocking density. Dermatitis, parasitic infections and systemic diseases should also be measured to

Some factors that have directly influenced this growth system are: improvement

of lines and inputs, automation of process systems, sanitary conditions for the creation of controlled birds, integrated production system, among others [50].

*DOI: http://dx.doi.org/10.5772/intechopen.96513*

and reduce some effects of stress or the harm of diseases.

(8%) and *Streptococcus* and *Enterococcus* [45, 46].

provide resistance to blood vessels, bones and skin.

**breast and white striping**

identify signs of poor well-being [49].

tissue vascularization.

#### *White Striping and Wooden Breast Myopathies in the Poultry Industry: An Overview of Changes… DOI: http://dx.doi.org/10.5772/intechopen.96513*

can alter and regulate the microbial ecology, to improve zootechnical performance and reduce some effects of stress or the harm of diseases.

In adult birds, when the microbiota is established, it may contain 400 to 500 microbial species [44]. With variations in the amount and types of microorganisms that may be attached to the epithelium or free in the lumen. When free, they may have an accelerated multiplicative capacity, minimizing loss through peristalsis, and may be associated with other bacteria that are linked to the mucosa. These variations mean that, in general, the small intestine is colonized by facultative microaerophilic bacteria, with their respective representation (in percentage) in the microbiota, which is: *Lactobacillus* (70%), *Clostridiaceae* (11%), *Streptococcus* (6.5%), *Enterococcus* (6.5%). The cecum, on the other hand, has mandatory anaerobic bacteria such as *Clostridiaceae* (65%), *Fusobacterium* (14%), *Bacteroides* (5%), and is also permeated by facultative microaerophilic bacteria such as *Lactobacillus* (8%) and *Streptococcus* and *Enterococcus* [45, 46].

A study by [47] who investigated the microbiota of WB and normal birds to understand the differential expression of plasma metabolites, obtained different results between groups, with non-myopathic broilers produced more heat, with higher body protein content, validated by the higher protein: fat ratio. Lower protein content in myopathic birds was verified, due to the probable high myiodegeneration, as observed by the high expression of 3-methylhistidine in plasma. In this work, the authors also reported that there was a predominance of unclassified Lactobacillus in birds with myopathy; while the species, L. acidipiscis was the predominant bacterium for non-myopathic broilers. The differentially significant metabolites identified in the plasma metabolome between the two groups were homocysteine, cyclic GMP, trimethylamine N-oxide, tyramine, carnitine and acetylcarnitine, all associated with the cardiovascular system. The results of this work suggest that more research on broilers should be carried out with a focus on tissue vascularization.

As WS and WB are proven to be inflammatory processes that permeate the entire carcass, it is possible to raise the hypothesis that alteration in the microbiota may be determinant for birds to be predisposed to develop these anomalies, consequently, there may be changes in the absorption of limiting amino acids or even essential for the synthesis of important proteins such as collagen and other proteins that can provide resistance to blood vessels, bones and skin.
