DEEP PECTORAL MYOPATHY IN BROILER CHICKEN MEAT OBTAINED FROM A SUPERMARKET - CASE REPORT, LITERATURE REVIEW AND PREVENTIVE MEASURES

Th e fast growth rates in commercially reared chickens could lead to the changes in their muscle tissue structure and cause breast muscle myo-pathies, including deep pectoral myopathy (DPM). Th e incidence of DPM depends on various factors including rearing conditions, age, sex, weight and genetic strain. Th e aims of the present paper were to report a case of DPM in broiler chickens bought in a supermarket and review important information regarding this disease from the available literature, especially its eff ect on meat quality parameters and consumer preferences.


INTRODUCTION
Broiler chicken meat industry is of great importance and it is well known that poultry meat is one of the main sources of protein for the people worldwide. Th e use of novel technologies and rapid development of genetic, farm management and nutrition are the main reasons why poultry meat industry is growing so fast. Some of the reasons for increasing demand for poultry meat are also modern trends and growing interest in healthy eating habits. However, the fast growth rate in commercially reared chickens could lead to the changes in their muscle tissue structure and cause breast muscle myopathies.
Deep pectoral myopathy (DPM) is also known as Green Muscle Disease and Oregon Disease. DPM was fi rst described in adult turkeys by Dickinson et al. (1968), while in young broiler chickens it was fi rst described by Richardson Arhiv veterinarske medicine, Vol. 15, No. 1, 43 -53, 2022 Ljubojevic Pelic, D… et al.: Deep pectoral myopathy… et al. (1980). Th e appearance of unusual green color in breast meat of commercially reared poultry is typical for this condition. It has been reported mainly in turkeys, but in recent years this disease has become more common in broiler chickens. DPM is not connected with any infectious diseases or harmful substances (Pastuszczak -Frak and Uradziński, 2009). It doesn't represent food safety concern. However, it signifi cantly aff ects the visual appearance of the chicken breast meat. Furthermore, alterations in visual sensory properties of the breast meat could negatively aff ect consumer acceptance of chicken meat (De Carvalho et al., 2020). Also, it could lead to meat quality losses (Yalcin et al., 2018). Th is condition is also a signifi cant economic problem in the poultry farming. It should be pointed out that breast muscles of broiler chickens are their economically most profi table part. Due to the fact that DPM signifi cantly aff ects meat quality of commercially reared chickens and has a negative economic impact, it represents a challenge to the broiler industry.
Th e aims of this paper were to describe a case of DPM in broiler chickens obtained from a supermarket and review important information from the available literature. Th is is very important, especially because consumers need to be able to recognize this disease. Finally, some recommendations for preventive measures and monitoring of DPM in poultry meat are proposed.

CASE PRESENTATION
No ethical approval was obtained because this study did not involve laboratory animals. It only involved non-invasive procedures.

Case report -consumer complaint report
Consumers bought four "ready to grill" chickens in a supermarket and, aft er realizing that the breast meat had a strange color and texture, they contacted the laboratory of Scientifi c Veterinary Institute "Novi Sad". All chickens available at the supermarket are produced on the same broiler chicken farm. Th e consumers were very distressed and concerned. Th ey found green fl esh inside chicken breasts and they described it as "atypical, greenish, breast resembling vomit in color that smelled strange". Th ey explained their surprise at the discovery, describing the meat as "absolutely disgusting". Furthermore, they said that the changes they encountered were like "fi nding a foreign body, a possible biological weapon" and "the emergence of a new parasite". Th ey bought four originally packed chickens "ready to grill" and found the changes in two, while cutting the chickens into pieces, to freeze them. Th ey claimed that they won't shop at that supermarket ever again. Additionally, they said that they had been raising chick-ens for years and had never encountered a similar problem. Obviously, consumers identifi ed this condition as an important health and aesthetic issue.

Organoleptic analysis
Th e consumers brought two carcasses of chicken meat that they bought at a supermarket to the laboratory of Scientifi c Veterinary Institute "Novi Sad". Sensory assessment was carried out in the laboratory.

Organoleptic characteristics of chicken meat
Th e changes in color were notable as green discoloration. Th ere were also the changes in the texture of breast muscles. Bilateral macroscopic changes of breast muscle that was green in color, as well as dry, crumbly, friable and solid consistency were observed during the examination. Dry appearance was also detected on the section. Progressive degeneration of the Pectoralis minor muscle and the damaged muscle tissue were found. Also, the unpleasant smell of the aff ected tissue was detected. Th e meat was repulsive. Th e diagnosis of DPM was established on the basis of distinctive green color of the muscle tissue and overall organoleptic characteristics ( Figure 1).

DISCUSSION
Th e aff ected muscle tissue should be removed and the rest of the carcass is fi t for human consumption. Due to the fact that the most valuable part of the chicken carcass is aff ected and removed, the quality of the product is significantly lower, which results in economic losses.
All the above mentioned indicates that there is a need to properly inform the public about such cases and conduct researches in order to prevent the unnecessary spread of fear and panic.

Th e main risk factors associated with the occurrence of DPM
Slaughter weight, rearing conditions, age, sex, genetics and mobility of chickens are the main factors associated with the occurrence of this disease (Petracci and Cavani, 2012). A major factor for the occurrence of DPM is undoubtedly rearing conditions. It is well known that the live weight of broiler chickens and turkey increased by more than two times over the last 50 years mainly due to the size of pectoral muscles (Semenova et al., 2019). An increase in incidence of DPM is connected with the increase in growth rate and muscle size. Petracci and Cavani (2012) came to the conclusion that the main problems related to occurrence of DPM in broilers are related to the selection of the chickens for growth rate and breast yield. It is known that heavier turkeys and broiler chickens have a higher incidence of this disease. Pajohi-Alamoti et al. (2016) found a signifi cant link between chicken's age, weight and occurrence of the disease. Furthermore, broiler chickens are mostly inactive during the growing period in commercial farming conditions. Th e consequence is that the breast muscles are not active enough and therefore they cannot expand due to the lack of physical activity. Consequently, some rapid and immoderate wing activity could lead to degeneration and death of the cells in muscle tissue. Discoloration of the fl esh is caused by swelling and represents a result of defi ciency of oxygen in the breast muscle due to improper blood supply. Distinctive swollen reddish-brown lesions appear fi rst and they are followed by lesion changes in color to green. Eventually, the lesions become pale green (Stangierski et al., 2019). Earlier fi ndings showed that pathological changes affect both major and minor pectoral muscles (Pastuszczak et al., 2002).
Mechanical stresses which could occur during contracting of myofi bers and inadequate energy metabolism are listed as the cause of muscular degeneration. Some other chicken breast meat abnormalities such as spaghetti meat, whitestriping and wooden breast are also associated with intensive broiler production conditions as a result of pushing biological boundaries (Petracci et al., 2019).
It is very interesting that DPM was observed in free-range broiler chickens. Bilgili and Hess (2002) reported that DPM was more frequently found in males than in females. However, Lien et al. (2012) reported that DPM was more frequently found in females. Bianchi et al (2006) concluded that genetics plays an important role in the development of this condition. Kijowski  Only one study related to DPM has been conducted in Serbia so far, at a slaughterhouse for fattening chickens from intensive housing conditions (Maslić-Strižak et al., 2014). Th e incidence did not depend on sex and in the examined hybrids it was 0.36% and 0.60%. No research has been conducted on the prevalence of DPM in chicken carcasses on the market.

Eff ects of DPM on poultry meat quality
Th e nutritional quality is the main reason for the fact that chicken meat is appealing to consumers worldwide, so the measures to preserve the quality of chicken meat are very important. Th e most signifi cant quality attributes for poultry meat are appearance and texture (Giampietro-Ganeco et al., 2022). Meat color is important for consumers when they decide to buy raw meat in the marketplace. Meat texture is also very important when choosing poultry meat. Dransfi eld and Sosnicki (1999) reported that toughness and poor cohesiveness, color and water holding capacity are the main meat quality problems connected with the selection for muscle growth.
Pastuszczak-Frak and Uradziński (2009) examined the hygienic and technological value of turkey meat originating from fl ocks with DPM and concluded that the meat was suitable for consumption from microbiological viewpoint. However, the technological value of the aff ected meat was diminished. Deviations in pH value, water binding capacity, color and chemical composi-tion were observed. Th ey reported that the meat aff ected with the DPM shows signifi cant diff erences in cross-section color, juiciness and taste aft er thermal processing. Cavalcanti et al. (2021) concluded that the severe condition of DPM causes variation in the quality of turkey muscle. Th ey observed color changes in affected meat samples. Also, they observed a greater water-holding capacity, pH, length of sarcomere, fat content and lower shear force and moisture content in the aff ected samples in comparison to nonaff ected samples. Th is is significant from the viewpoint of the manufacturing of processed products since fat content and water holding capacity represent crucial meat properties. Th ey suggest that the processing represents a proper alternative for exploitation of aff ected meat. DPM aff ects the color and partially a reduction of texture of the breast meat which are the main attributes for consumers and chicken's most valuable part, which consequently has a negative economic impact on broiler meat industry (Giampietro-Ganeco et al., 2022). Cavalcanti et al. (2021) concluded that the processing is an economically feasible potential for the commercialization of aff ected breast meat.

Consumers' acceptability of DPM
Th e main problem (with DPM) is the absence of symptoms (while chickens are) on the farm. It can be identifi ed only during carcass dissection. Th e additional problem occurs when whole chickens are sold. Th e consumers normally detect the changes when cutting the chickens into pieces. Th ey observe changes in color and texture of the muscles. Consumers recognize the observed changes as signs of spoilage. Th e main problem could be the fact that consumers will no longer trust the producer and they will refrain from buying chickens and other products in the future (Kijowski et al., 2014).
Consumers' attitude towards green muscle diseases should be regarded as an important and relevant issue. Th ey have the right to know and choose what they want to eat. Consumers identify these changes as uncommon for chicken meat. Th e changes reduce the visual acceptability of chicken breasts and even the whole carcass. Unpleasant green color which appears when the chickens are cut scares the consumers despite the fact that meat is safe for consumption. De Carvalho et al. (2020) noted that the consumption of fresh poultry meat in some European countries decreased. Th e image of modern poultry farming system and a changed perception of poultry meat quality and safety are the important reasons for the above-mentioned decreasing trend in poultry meat consumption. Th e recognition of DPM may have negatively aff ected the consumer's attitude by associating the green muscle diseases with unhealthy and unsafe meat.
In the future, these conditions could lead to an increasing number of consumer complaints mainly due to the fact that it is regarded as an unpleasant "surprise" during preparation. Th e aff ected meat is unfi t for consumption, it is sensory -organoleptic unacceptable.

Preventive measures and detection of DPM
Th e main problem is the fact that DPM is usually undetected until processing. Also, it is very diffi cult to predict the occurrence of this condition. DPM leads to signifi cant economic losses due to the fact that it aff ects chicken breast which is the most valuable part of the carcass. During processing of chickens, the aff ected muscle tissue is removed.
Management practice on the farm is the most important preventive measure against DPM. Minimizing wing-fl apping is the best preventive measure. It is very important to monitor health conditions of chickens, ventilation, air quality, ammonia level, temperature, etc. Also, the time that people spend in broiler farm should be limited. Noise levels and amount of light that could frighten the chickens should be minimized.
Recently, creatine kinase was identifi ed as a blood enzyme that could be a noninvasive tool for breeders to screen birds for susceptibility to the disease. However, this method is not applicable in commercial poultry farms due to the time needed for analysis and high costs (Kijowski et al., 2014). Also, genetic selection against DPM could be an eff ective tool for reducing the future occurrence of DPM (Petracci et al., 2015). Petracci and Cavani (2012) reported that genetic selection against DPM has been undertaken by poultry companies. Th ey also reported that developments in whole-genome selection using dense DNA -markers could be signifi cant in reducing the occurrence of this disease in the future.
A non-destructive sensor able to detect DPM in whole carcasses has been developed (Traff ano-Schiff o et al., 2018). Th e sensor measures the permittivity of chicken whole carcass with skin in depth. Th is method could be commercially available in future.
Th e presented data are very important for consumers, poultry farmers, poultry abattoirs, poultry suppliers, veterinary practitioners, inspectors and scientifi c community. Th ere are no clinical signs of DPM and it could be detected only aft er dissection of carcasses. Th e diagnosis is confi rmed by macroscopic examination. Th e main problem is the fact that this condition is only noticed aft er the broilers are slaughtered. DPM has important eff ect on meat quality. Such meat is aesthetically undesirable so the changed parts of meat should be removed and the rest of carcass is fi t for human consumption. Th e fact that DPM aff ects the most valuable parts of poultry carcass leads to signifi cant economic losses.
Th is the only case of DPM which has been reported and confi rmed in the laboratory for microbiological and sensory analysis of food of the Scientifi c Veterinary Institute "Novi Sad" so far. Due to the extreme concern of consumers, we considered it important to describe this case and draw attention to this disease. Th e presented data is of public interest and it could signifi cantly contribute to the consumers' knowledge about the disease.
A proper solution to this disease is not currently commercially available.

Author's Contribution:
DLJP and MP made substantial contributions to basic idea, conception and design, acquisition of samples and data, analysis of the data and interpretation of results; JV, BP, NN and SVK were involved in draft ing of the manuscript, revising it critically for important intellectual content, and DLJP and MŽB gave the fi nal approval of the manuscript to be published.