Limited wing extension is associated with woody breast in broilers and their inability to self-right

The fact that woody breast (WB) is currently detected only post-mortem limits our understanding of this economically relevant broiler myopathy. We aimed to determine whether restricted wing movement could serve as a non-invasive indicator of WB in live birds, and whether it would affect a broiler's ability to self-right. We tested 58 fast growth broilers across three commercial farms within two days of market age (45-52 days of age). Broilers were categorized based on the distance between the glenohumeral joints measured to the nearest half centimeter across the back while the wings were extended backwards: complete extension (0 cm), moderate wing partition (1.5-5 cm) and pronounced wing partition (≥ 5.5 cm). Each broiler was then placed on its back, and time to self-right was recorded (up to 60 s maximum). Post-mortem palpation of the Pectoralis major muscle was used to assess WB severity. Moderate or pronounced wing partition detected WB with an accuracy of 93.1%, sensitivity of 95.5%, specificity of 85.7%, positive predictive value (PPV) of 95.5%, and negative predictive value (NPV) of 85.7%. Pronounced wing partition detected severe WB with an accuracy of 82.8%, sensitivity of 84.6%, specificity of 81.3%, PPV of 78.6%, and NPV of 86.7%. Self-righting was affected by both wing partition and WB presence and severity. Broilers with a pronounced wing partition were less likely to self-right than those with no or moderate wing partition (one-tailed Fischer's Exact Test, p < 0.05). All 14 broilers without WB successfully righted themselves whereas only 6 of 26 broilers with severe WB were able to do so. The median times to self-right differed by WB severity (Kruskal-Wallis χ² = 24.36, p < 0.05; 1.36 s, 1.86 s, and 60 s for broilers without WB, with moderate, and with severe WB, respectively). Our findings show that wing partition is an accurate, non-invasive indicator of WB in live birds. Furthermore, pronounced wing partition is associated with impaired self-righting ability reflecting a bird welfare concern.