Blood Stress Hormonal Indicators and Meat Quality Attributes of Broiler Chickens Processed Using Electrical and Controlled Atmosphere Stunning Systems

Abstract

Increased consumer concern for animal welfare has led some poultry producers to alter their stunning methods from electrical stunning (ES) to controlled atmosphere stunning (CAS). However, there is little peer-reviewed research available comparing the two methods within a commercial setting under U.S. parameters. We conducted two studies to evaluate both CAS and ES methods and their impact on circulating blood-stress hormones and meat quality aspects of broiler chickens within a commercial setting. As a brief explanation, our first experiment was conducted within a commercial facility, where blood samples were collected from broilers stunned by either CAS or ES at lairage, pre-stun, and post-stun. Two separate trials were conducted, Trial 1 having the same flock analyzed for each treatment, and Trial 2 with each treatment sample collected from birds of differing flocks. CORT, ACTH, EPI, and NOREPI concentrations were analyzed by ELISA. We observed that CORT decreased following ES in both Trials 1 and 2. In Trial 2 EPI increased post-stun. Neither ACTH nor NOREPI differed over time in either trial for ES birds. For CAS, CORT concentrations decreased post-stun in Trial 1, but did not differ in Trial 2. ACTH concentrations post-stun increased in Trial 1 but decreased in Trial 2. EPI and NOREPI concentrations did not differ over time for CAS birds. Based on these results, CORT, ACTH, EPI, and NOREPI did not respond in the same manner and trends differed between stunning methods. Results indicate that neither method of stunning was clearly preferable based on measurement of blood hormone indicators of a stress response. For our second study, occurrence of visible wing damage was evaluated post-defeathering and breast fillet meat quality was evaluated through measurement of pH, CIE-LAB values, and drip loss. Values were determined both at deboning and 24 hours after deboning. Blood glucose concentrations (mg/dL) from CAS and ES birds differed only at post-stun, with glucose from birds stunned by CAS significantly higher than ES (418, 259, P<0.0001). Breast fillet quality did not differ between broilers stunned by either electrical or CAS. CAS carcasses had significantly more visible wing damage than ES carcasses (4.3%, 2.4%, P<0.0001). Drip loss did not differ between breast fillets of CAS or ES broilers. The implications of increased blood glucose concentration post-CAS are currently unknown and will require further evaluation. Increase in visible wing damage observed post-defeathering from CAS carcasses indicated a need for equipment parameter adjustments and further evaluation. Overall, the results of both studies indicate that there are some differences in blood-stress indictors at differing timepoint of either CAS or ES, as well as significantly more wing damage and glucose after CAS. Further evaluation is required to determine the exact reasoning behind these results.