Heavy broilers tough problem: white striping, woody breast

Because white striping and woody breast conditions in broiler chicken meat are closely linked to economically important live production and carcass yield traits, these meat quality defects pose a substantial challenge to the poultry industry.

Normal breast fillets free of the woody breast condition exhibit normal hardness and rigidity upon palpation. | Brian Bowker
Normal breast fillets free of the woody breast condition exhibit normal hardness and rigidity upon palpation. | Brian Bowker

In order to meet increasing consumer demands for high quality poultry meat products, the U.S. broiler industry has utilized genetic selection and improved feeding and management practices to achieve remarkable gains in broiler size, growth rate, feed efficiency and carcass yield over the last 50 years. An increasing proportion of birds are being raised to heavier weights in response to market shifts from consumers buying whole bird carcasses to cut-up parts and to more efficiently meet the needs of the further processing industry. Unfortunately, along with the gains in bird size and growth rate, there has been an increasing incidence of the white striping and woody breast defects in modern broilers.

The white striping condition is characterized by visible white striations running parallel to muscle fibers in breast, tenders and thigh muscles. Breast fillets with the woody breast condition exhibit abnormal hardness and rigidity upon palpation and a ridge-like bulge on the tail end of the fillet.

Severe-woody-breast-chicken

White striping is characterized by visible white striations running parallel to muscle fibers in breast, tenders and thigh muscles. | Brian Bowker

White striping, woody breast incidence and impact

Although industry-wide incidence rates are difficult to assess, available data on various research and commercial flocks suggest that the incidence of severe white striping could be as high as 25 percent to 30 percent. It has been estimated that 5 percent to 10 percent of commercially produced breast fillets exhibit woody breast. The incidence rates of moderate degrees of white striping and woody breast could be even greater. Even at low incidence rates, the costs to the industry can be substantial as breast fillets exhibiting severe white striping or woody breast are often downgraded and sold at a discount, used for further processing or, in extreme cases, discarded.

While their relationship is not fully understood, evidence suggests a connection between the white striping and woody breast conditions. Although breast fillets often have white striping without the woody breast condition, most fillets that exhibit woody breast also have white striping. Histologically, both white striping and woody breast fillets exhibit muscle fiber degeneration, necrosis, lymphocyte and macrophage infiltration, lipidosis and fibrosis. Compositionally, these changes result in breast meat with increased levels of fat and connective tissue and decreased muscle protein content. Recent studies have also shown that fillets with the white striping and woody breast abnormalities have altered mineral profiles.

The incidence of severe white striping could be as high as 25 percent to 30 percent and the incidence of woody breast as high as 5 percent to 10 percent of commercially produced breast fillets.

Problems with breast meat appearance, tenderness

The increasing occurrence of these myopathies is problematic for a number of reasons. Increased visible fat on boneless skinless breast fillets can give the consumer the perception that the product is less healthy and negatively impact purchasing decisions. Sensory evaluations have shown that abnormal texture attributes are detectable in cooked woody breast fillets. Shear force differences in tenderness between woody breast and normal fillets even persist through postmortem storage and freezing/thawing. Differences in muscle fiber shortening during rigor development have not been observed in woody breast fillets, suggesting that the increased hardness of woody breast fillets is likely due to their high connective tissue content.

Although the objectionable texture characteristics of woody breast fillets can be overcome through grinding, the compositional changes can result in impaired functionality in further processed products. The white striping and woody breast conditions have been shown to decrease marinade pick-up and increase cook loss in breast meat. Research has also suggested that fillets with moderate and severe white striping have reduced nutritional quality due to elevated fat content and diminished protein quality and content.

Meat-composition-and-quality-comparisons

White striping and woody breast conditions have been shown to decrease marinade pick-up and increase cook loss in breast meat.

Most frequent in fast-growing, high breast yield

Although the white striping and woody breast conditions are most readily apparent after processing, these myopathies develop over time in the live birds. A potentially important question that has yet to be addressed is whether or not these myopathies, particularly woody breast, impact animal welfare in the live birds.

Factors associated with the incidence of white striping and woody breast have been reported, but the specific etiologies of white striping and woody breast are unknown. It is well-accepted that the white striping and woody breast conditions occur most frequently in fast-growing broilers with high breast yields that are grown to heavy weights. Factors influencing the growth, muscularity, and size of the birds such as slaughter age, gender, genetics and feeding have all been associated with the incidence and severity of these myopathies.

The development of accurate biomarkers will allow the industry to more effectively assess the influence of genetics, feeding, and management on the occurrence and severity of these myopathies.

Even prior to the first reported studies on white striping and woody breast, it had been hypothesized that the selection of broilers for accelerated growth and breast meat yield could inadvertently lead to growth related myopathies, inherent muscle fiber defects, and insufficient capillary and fascial growth. A number of studies supported this hypothesis and suggested that fast growth rates in broilers may be related to reduced capillary density, altered cation regulation, and greater metabolic stress within the muscle tissue and an overall reduced thermoregulatory capacity within the birds.

Search for causes of white striations, woody breast

The white striping and woody breast conditions cause both macroscopic and microscopic changes to the breast muscle tissue similar to other myopathies known to exist in poultry. In a recent review article (Kuttappan, V., Hargis, B., and Owens, C. 2016. "White striping and woody breast myopathies in the modern poultry industry: a review." Poult. Sci. https://dx.doi.org/10.3382/ps/pew216): The white striping and woody breast conditions were compared to hereditary muscular dystrophy, nutritional myopathies due to vitamin and mineral deficiencies, deep pectoral myopathy and toxic myopathies from ionophore usage. Although the white striping and woody breast conditions can cause similar histopathological and compositional changes to the muscle tissue as some of these other myopathies, the available research does not indicate a direct connection. In an attempt to delineate the underlying causes of white striping and woody breast and to identify potential biomarkers, several recent studies have compared the gene and protein expression profiles and the metabolite profiles of normal breast muscles with those exhibiting white striping and woody breast. These genomic, proteomic and metabolomic studies observed differences related to muscle hypoxia, oxidative stress, intracellular calcium levels, protein degradation, cellular repair, fibrosis and glucose utilization in myopathic fillets (Zambonelli, P., Zappaterra, M., Soglia, F., Petracci., M., Sirri, F., Cavani, C., and Davoli, R. 2016. "Detection of differentially expressed genes in broiler pectoralis major muscle affected by white striping – wooden breast myopathies." Poult. Sci. http://dx.doi.ort/10.3382/ps/pew268).

The findings of these advanced studies are consistent with the histological and biochemical characteristics observed in white striping and woody breast fillets, but do not clearly identify the trigger that induces such changes within the tissue.

Gene expression data suggest that the white striping and woody breast myopathies have multi-faceted and complex etiologies. Future research using these advanced approaches at different time points during the broiler growth cycle may help to uncover the causes of the white striping and woody breast conditions and identify biomarkers. The development of accurate biomarkers will allow the industry to more effectively assess the influence of genetics, feeding, and management on the occurrence and severity of these myopathies. 

A potentially important question that has yet to be addressed is whether or not these myopathies, particularly woody breast, impact animal welfare in the live birds.

While the ultimate goal of the industry and research communities should be to discover the specific causes of these myopathies and to identify methods to reduce their occurrence, research is also needed to develop more standardized and objective methods for measuring the incidence and severity of the white striping and woody breast conditions. The white striping and woody breast conditions are typically identified and categorized using subjective visual and tactile assessments of boneless skinless breast fillets. Various institutions are investigating the potential for using air deformation measurements, compression force and imaging based technologies for detecting the woody breast condition in raw breast fillets. The future development of rapid non-invasive techniques to identify the occurrence and severity of the woody breast and white striping conditions would provide the industry with valuable tools for online meat quality monitoring and product segregation.

Nutritional and genetic strategies sought

As the white striping and woody breast conditions seem to be closely linked to economically important live production and carcass yield traits, these meat quality defects pose a substantial challenge to the poultry industry. Although research suggests that slower broiler growth rates or decreased slaughter weights and ages may lessen the occurrence and severity of white striping and woody breast, such trade-offs would be detrimental to the overall production and processing efficiency of the industry.

Although much has been learned about the white striping and woody breast defects over the last few years, more research is needed. Much of the research to date has focused on describing the changes that occur at the muscle tissue level and their implications on meat quality, composition and processing functionality. As researchers have learned more about the distinguishing attributes of the woody breast and white striping conditions, more efforts are being made to identify biomarkers for these myopathies in live birds and to develop technologies that can be used by the processing industry to more effectively manage the problem through online meat quality assessment and product segregation.

As research efforts shift from characterizing these myopathies to searching for the underlying causes, hopefully viable nutritional and genetic strategies can be developed to reduce the occurrence of the white striping and woody breast defects while still maintaining fast growth rates, feed efficiency and high meat yields.

 

 

Read more:

Nutritional strategies to reduce woody chicken breast, www.wattagnet.com/articles/28248

Page 1 of 33
Next Page