Short communication-characterizing heart rate of beef cattle during stunning and exsanguination at slaughter

The objective of this study was to evaluate the changes in heart rate (HR) during stunning and exsanguination in slaughter-weight cattle stunned one (Experiment 1) or two (Experiment 2; one initial and one security stun) times with a penetrating captive bolt gun. Data were collected between April 2025 and April 2026. In Experiment 1, 21 steers (n = 21; BW = 662 ± 65 kg) were used, and in Experiment 2, 5 steers and 4 heifers (n = 9; BW = 666 ± 72 kg) were used. All cattle were fitted with a HR monitor while restrained in a hydraulic squeeze chute and were transported to the university processing facility for slaughter. In both experiments, cattle were stunned (time 0 s) and rendered insensible with a pneumatic penetrating captive bolt stunner. Experiment 1 utilized one stun, and Experiment 2 implemented a secondary security stun (with a handheld captive bolt stunner) approximately 20 s after the first stun. HR was recorded from 60 s prior to stunning until 10-15 min post-stunning. Data were aggregated into 1-s intervals. Prior to stunning (-60 s - 0 s), HRs in both Experiments were elevated compared to typical resting HR in cattle, with an average of 141 beats per minute (bpm) in Experiment 1 and 120 bpm in Experiment 2. Immediately following captive bolt administration, HR increased rapidly, reaching an average peak of 165 bpm within approximately 12 s in both Experiments. After that, HR decreased, reaching a low near exsanguination and then peaked a second time (134 bpm at approximately 4 min post-stun and 120 bpm at approximately 2.7 min post-stun in Experiments 1 and 2, respectively). HR steadily declined as animals approached clinical death, reaching a plateau of 30-40 bpm at approximately 9 min post-stun, the bpm likely representing residual electrical impulse activity of the heart. Overall, the results provide a clear indication of HR in cattle under slaughter conditions and are relevant to discussions around the timing of cardiac death in cattle.