Abstract 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. HIGHLIGHTS Wooden 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.

中文翻译：

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木胸肉鸡的肌节长度

摘要 本研究旨在测量正常肉鸡肌肉和受木制乳房（WB）影响的乳房肌肉非病变部位的肌节长度。为此，对 20 块胸大肌（10 块未受影响和 10 块 WB 局灶性受影响的病例）进行采样，并用于通过激光衍射法测量肌节长度。与未受影响的对应物相比，WB 病例在肌肉的非损伤部位测量的肌节长 13%（1.91 对 1.69 μm；p < .001）。虽然基于非病变区域得出关于病变特性的结论并不简单，但由于纤维彼此结合，因此可以合理地预期 WB 中观察到的硬化稠度并不归因于更强烈的肌节收缩。此外，考虑到目前关于这种情况的知识，可以假设在 WB 中观察到的较长的肌节不会触发这种情况的发展，而是由此导致的肌肉结构发生深刻变化的结果。事实上，尽管在活体和屠宰性状方面取得了显着改善，但过去几年进行的选择程序导致快速生长的杂种胸大肌的毛细血管化减少和氧气供应受损，从而影响其构成纤维的生理学以及可能会削弱他们合成新肌节的能力。这可能导致骨骼肌损伤，最终导致坏死和纤维化。亮点 木制乳房不太可能与肌肉过度收缩有关，但可能是肌肉劳损增加的结果；在人类肌病肌肉中观察到的类似特征支持类似潜在机制的假设。