Research shows fast growth leads to breast meat issues

Researchers are better understanding the cause of breast meat abnormalities like woody breast syndrome, but a comprehensive solution to these problems remains elusive.

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(Boida Anatolii I shutterstock.com)
(Boida Anatolii I shutterstock.com)

Researchers are better understanding the cause of breast meat abnormalities like woody breast syndrome, but a comprehensive solution to these problems remains elusive.

As part of the American Meat Science Association’s virtual 66th International Congress of Meat Science and Technology and 73rd Reciprocal Meat Conference, held between August 3 and August 6, 2020, Dr. Massimiliano Petracci, a full professor at the University of Bologna’s Department of Agricultural and Food Sciences, spoke about the current state of research surrounding breast meat abnormalities.

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Massimiliano Petracci, University of Bologna (Carlos Suarez)

He said the common origin of breast meat abnormalities is the fast growth of the muscle tissue. Absent other solutions, signs could be pointing toward a partial transition from the standard, faster-growing broiler bird to a differentiated market with price premium products coming from birds with non-standard genetics.

Origins of the abnormalities

Petracci said the abnormalities originate in the relatively recent integration of the poultry industry around the world since the end of the second world war. Thanks to focused genetic progress and the vertically integrated nature of the market, the bird is now growing too much larger sizes in much shorter times than it ever could in the wild.

However, he said, that progress toward faster weight gain is contributing to the development of several breast meat abnormalities – such as woody breast syndrome, white striping and spaghetti meat – that do not affect nutrition but do affect the quality of both raw and processed meat and cause economic damages for the poultry industry.

He said selection for growth rate, breast meat and slaughter weight leads to many conditions – like higher inflammatory response and lowers antibody response, muscle hypertrophy and reduced vascularization – which contribute to breast meat abnormalities. Breast meat abnormalities were first detected in the 1980s in the pectoralis minor muscle, or tender, but are significantly increasing in incidence in the pectoralis major, or breast, since 2009.

He described the abnormalities as: 

  • White striping: Abnormal white striations parallel to muscle fibers within the superficial layer of the cranial region of the pectoralis major muscle.
  • Woody breast: Visibly hardened consistency, prominent caudal ridge often associated with paleness, superficial viscous fluid and petechiae, or spots caused by bleeding under the surface of the muscle.
  • Spaghetti meat: A tendency toward the separation of the fiber bundles composing the pectoralis major muscle forming a spaghetti-like appearance.

Petracci cited recently conducted studies in the U.S. which found that birds slaughtered at 9 weeks of age are likely to display severe and very severe incidences of white striping and woody breast. In the study, 69% of birds displayed either severe or very severe white striping and 51.2% of birds displayed either severe or very severe woody breast. Another study he cited found that often, both conditions occur in the same bird.

Commercial consequences

The commercial effect of these syndromes is a lowering of meat quality. For whole or portioned products sold raw to consumers, what matters is the stability of the meat, its appearance in packaging and its tenderness. For further processed products, the water-binding capacity, stability, texture, juiciness and aroma are key.

Breast muscles affected by the specific abnormalities are downgraded because poor appearance affects its consumer acceptability. When it is downgraded, it heads to further processing. However, when it is used for that purpose the meat does not exhibit the same liquid retention, water-binding capacity or tenderness as normal meat. He cited a recent study which showed woody breast cannot pick up marinate solution as well as normal meat, too.

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Recent studies in the U.S. show a high occurrence of breast meat abnormalities (left to right, spaghetti meat, white striping and wooden breast) in birds slaughtered at 9 weeks. A reported 69% of birds displayed either severe or very severe white striping and 51.2% of birds displayed either severe or very severe woody breast. (Kylie Philipps) 

Causes of the conditions

In the past decade, Petracci said many studies were conducted to understand the origins of the breast meat abnormalities.

Nevertheless, science is pointing toward a common origin for the three conditions: fast pectoralis major muscle growth.

The fast growth leads to oxygen deprivation. This condition leads to an inadequate supply of nutrient supply to the tissue, impaired metabolic waste product displacement and further stress to muscle tissue due to an increased protein deposition and altered calcium homeostasis.

These conditions lead to inflammation, impairment of immune system function and, ultimately, muscle fiber degeneration and regeneration that manifests in lipidosis or fibrosis.

Specifically, for spaghetti meat, there is a detachment of the muscle fibers and a disfunction of collagen turnover and synthesis which causes a breakdown of connective tissue in the muscle.

Possible next steps

Despite the studies conducted in the past decade, Petracci said, there is no efficient solution capable of inhibiting the onset or at least lessening the symptoms, of the muscular abnormalities. Furthermore, even with the increased downgrading of meat due to the abnormalities, genetic pressure toward fast growth is not changing because economic benefits, so far, are much greater than the penalties.

“In this scenario, further scientific research may address embryonic formulation of additional myofibers and feeding strategies as well as innovative processing solutions,” Petracci said.

Moreover, he said the increasingly negative perception and attitude toward intensive agriculture in the developed world may favor a partial transition from the standard broiler bird to a market composed of different, premium-priced products.

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