Producing high quality meat is a primary goal of the poultry industry. In the recent years, as chicken breeds are genetically selected for faster growth and larger breast meat, there has been an increase of myopathies (diseases of the muscle in which the muscle fibers do not function properly) mainly affecting the breast. The most frequent myopathies are white striping (white lines of fat tissue running through the breast meat) and woody breast.

Woody breast is a myopathy that is characterized by the breast meat being hard to the touch. This hardness can be present already in the live bird, as early as few weeks old, and can be detected by palpation. In the slaughterhouse, breast meat is scored using a rating system based on severity from 0 (no indication of woody breast) to 3 (severe).

Woody breast does not harm the animals and their meat is healthy to eat, but it affects their marketability. Compared to normal breasts, woody breasts:

• Have unpleasant texture and mouth feel
• The muscles are rigid and show a viscous exudate on the surface
• Lose more water before and during cooking
• Have a higher pH after slaughter
• Are less tender (higher shear force) before and after cooking

For all the above, woody breasts are unappealing, cannot be marketed to consume directly and are usually destined to produce ground meat.

It is estimated that 5-10% of the breast fillets produced worldwide show mild or severe woody breast conditions. Such a high incidence also increases the costs at the slaughterhouse, that needs to check the hardness of the breasts of each carcass after defeathering.

Metabolic consequences of woody breast

Broilers with high growth rate, feed efficiency and breast muscle yield are more prone to woody breast, because the muscle tissues grow disproportionally big and their normal metabolism cannot be properly supported by the connective tissue and the circulatory system.

During the woody breast syndrome, the metabolism and the structure of the muscle changes:

• The muscular fibers lose their normal structure and become larger
• The deposition of collagen and fats increases
• There is an infiltration of immune cells involved in muscle repair
• The blood flow in the breast muscle is reduced, making it difficult to supply oxygen and nutrients. Metabolic waste accumulates in the tissue.

As a result of the above, there is an increase of the concentration of free radicals, mainly reactive oxygen species (ROS), that produces oxidative stress in the muscular tissue. ROS start inflammation and induce changes in the muscle cells that ultimately lead to woody breast.