Bleedout efficiency, carcass damage, and rigor mortis development following electrical stunning or carbon dioxide stunning on a shackle line.

In Experiment 1, 400 male broilers were stunned using a gradient of 40 to 60% CO2 over a period of 25 s or a 1% brine solution that was electrically charged (35 mA) for 7 s. Blood loss during bleeding was measured in 30-s intervals for a total of 120 s. After conventional processing and chilling, carcass damage was subjectively evaluated. Results indicated that the birds stunned with electricity bled faster than the CO2-stunned birds until 60 s. However, the cumulative blood loss was not different after 90 s. Carcass damage evaluation indicated that birds stunned with CO2 had a significantly lower percentage of broken clavicles, and had fewer hemorrhages on the surface of the Pectoralis. However, there was no difference between the two stunning methods in the frequency of damage at the shoulder. In Experiment 2, 256 broilers were stunned using the same conditions as in Experiment 1. Measurements of pH, R-value, sarcomere length (SL), and fragmentation index (FI) were evaluated from the left breast fillets harvested at 0, 1, 2, and 6 h postmortem. Shear values (SV) were determined using the right fillets harvested at the same four postmortem times and aged on ice until 24 h. No significant difference in breast muscle pH value was observed at 0, 2, and 6 h postmortem. However, CO2-stunned fillets had significantly higher pH values than the ES fillets at 1 h postmortem. Carbon dioxide produced greater R values than electricity at 2 and 6 h. Sarcomere length, FI, and SV were not significantly different at any time tested. These data suggest that CO2 stunning reduced carcass damage but did not reduce the need for aging before deboning when compared to the electrical stunning method used.