Sarcomere lengths in wooden breast broiler chickens

The present study aims to measure the sarcomere lengths in normal broiler muscles and in non-lesion sites of breast muscles focally affected by Wooden Breast (WB). For this purpose, twenty Pectoralis major muscles (10 unaffected and 10 WB-focally affected cases) were sampled and used to measure sarcomere length by laser diffraction method. When compared with their unaffected counterpart, WB cases exhibited 13% longer sarcomeres (1.91 vs. 1.69 μm; p < .001) measured within the non-lesioned site of the muscle. Although it is not simple to draw conclusions about the lesion properties based on the non-lesion area, but as the fibres are bound to each other, it may be reasonable to anticipate that the hardened consistency observed in WB is not ascribable to a more intense contraction of the sarcomeres. In addition, considering the current knowledge concerning this condition, it might be assumed that the longer sarcomeres observed in WB are not triggering the development of this condition but are rather a consequence of the profound alteration in the muscular structure resulting from it. Indeed, despite the outstanding improvements in the live and slaughtering traits, the selection programmes carried out in the past years have resulted in a reduced capillarization and impaired oxygen supply to the Pectoralis major of fast-growing hybrids thus affecting the physiology of its constituting fibres as well as maybe impairing their ability to synthetise new sarcomeres. This may result in a skeletal muscle injury, which would ultimately lead to necrosis and fibrosis.HIGHLIGHTSWooden Breast is not likely associated to muscle hypercontraction but likely a result of an increased muscular strain; Similar traits observed in myopathic muscles in human support the hypothesis of a similar underlying mechanism.