Green muscle disease

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Deep pectoral myopathy

Also known as Green muscle disease

Deep pectoral myopathy occurs worldwide in growing turkeys and sometimes in heavy broilers. Deep pectoral myopathy causes the swelling in a tight fascia (band) of vigorously exercised muscle of growing birds. There is some evidence of hereditary predisposition, rapid growth rate and increased handling in turkey breeder hens during artificial insemination.

Causes of Deep pectoral myopathy

Ischaemia (inadequate circulation of blood) causes the swelling in a tight fascia (band) of vigorously exercised muscle of growing birds. There is some evidence of hereditary predisposition, rapid growth rate and increased handling in turkey breeder hens during artificial insemination. The condition is occasionally seen in heavy broilers.

The cause is a lack of oxygen due to improper blood supply or necrosis around tissues or blood vessels.

It is non-contagious and no specific nutritional factors may influence the condition.

Effects of Deep pectoral myopathy

This is a processing plant problem. Problems in the field are still limited, but can be expected in the coming years due to extreme selection for breast meat.

Postmortem lesions

Unilateral or bilateral lesions which do not affect the health of the bird may occur followed by more chronic lesions resulting in dimpling of flattening of the breast muscle which can be palpated.

The whole deep pectoral muscle is swollen, pale and oedematous with necrosis in the middle 1/3-3/5 of the muscle, which is only evident after processing or necropsy.

In other lesions, the oedema disappears and the necrotic muscle becomes more prominent and drier with greenish areas.

Necrotic muscle shrinks and may be enclosed in a fibrous capsule. The sternum adjacent to the necrotic muscle becomes roughened and irregular.

Diagnosis of Deep pectoral myopathy

Gross (greenish muscles) and microscopic lesions are characteristic. Microscopically the fibres are swollen and eosinophillic with discoid necrosis. Nuclei are absent or faint.

Surrounding the necrotic tissue are inflammatory reactions. Vascular lesions consist of thromboses, intimal proliferation and aneurysm formation.

It simulates bacterial (gangrenous), fungal (favus) or nutritional (exudative diathesis) dermatitis.