Induction of deep pectoral myopathy in broiler chickens via encouraged wing flapping

SUMMARY A reproducible method for inducing deep pectoral myopathy (DPM) in broilers was investigated. To induce DPM, broilers were subjected to encouraged wing flapping (EWF) by repeatedly raising and lowering them a distance of 1 m. Each cycle resulted in 1 bout of 4 to 6 flaps. At 45 d of age, no DPM occurred in control birds subjected to 0 cycles of EWF or those subjected to 5 cycles, whereas the prevalence of DPM (% of pectoralis minor muscles with lesions) was 7 and 33% in those subjected to 10 and 20 cycles of EWF, respectively. The prevalence of DPM in broilers subjected to 25 cycles of EWF at 49 d of age was 56% and was unaffected by sex or a 0.4-kg difference in BW. The involvement of DPM (i.e., % of muscle surface discolored) and the discoloration score (predominant color of lesions) were also unaffected by sex or BW. The prevalence of DPM at 48 or 120 h after EWF averaged 48% and was unaffected by time from EWF. However, involvement of DPM and discoloration increased with time from EWF, reflecting a change in lesion extent or visibility, and color. Susceptibility to EWF-induced DPM was observed at 26 d of age in males and 36 d of age in females. The prevalence of DPM was greater in males at 33 and 36 d, but was similar thereafter and was unaffected by BW. Therefore, the EWF method of DPM induction is useful for accentuating the occurrence of the disease to facilitate further study and that susceptibility to DPM is primarily associated with age above certain thresholds for each sex.