Deep pectoral myopathy is a degenerative disease, that causes injuries of minor
pectoral muscles in broiler chickens and turkeys. It is not a new disease, but it is
becoming increasingly more common in broiler chickens and turkeys selected for
rapid growth. It is possible that both pectoral muscles are injured but due to the
inelastic fascia surrounding the muscle and its tight location next to the sternum, the
minor pectoral muscle is more susceptible to disease. Minor pectoral muscle has the
main role at wing flapping (up-strokes). During contraction, minor pectoral muscle
increases its volume because of increased blood circulation to the muscle. The
specific location of the pectoralis minor muscle does not allow it to expand during
greater physical activity. The blood supply stops and muscular necrosis occurs as a
result of hypoxia and muscle malnutrition Longer exposure can lead to tissue
breakdown. The interruption of oxygen supply in the minor muscle is connected with
fast wing flapping. The development of the disease can be divided into three stages.
At the beginning the muscle tissue starts to swell. Muscle is red to brown coloured,
later becomes green to light green. Also the muscle pH falls. Because the disease is
not reflected in a change in the animal's health, it is difficult to detect it in a flock of
animals while they are still alive. The lesions on the meat can be seen at the time of
deboning in the slaughterhouse. The key to reduce the deep pectoral myopathy lies
in proper breeding technology, management on the farm and actions that reduce
unnecessary wing flapping.
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