Head-only followed by cardiac arrest electrical stunning is an effective alternative to head-only electrical stunning in pigs1

Many small slaughter facilities use head-only electrical stunning to render swine unconscious and insensible to pain before slaughter. Head-only electrical stunning is a reversible procedure that is optimally effective for approximately 15 s after stun completion. In many small North American slaughter plants, the authors have observed hoist speeds that are too slow to achieve a short enough stun-to-bleed interval to maintain insensibility through exsanguination. Unlike many European plants, there is no separate high-speed hoist for pigs and exsanguination on the floor is not condoned. As a result, a 2-stage stunning method was proposed where head-only stunning for 3 s was immediately followed by application of the same stunning wand to the cardiac region of the animal for 3 s while lying in lateral recumbancy. A paired-comparison study was conducted on 89 pigs in a small slaughter facility to compare the head-only method applied for 6 s with the head/heart method. The objective was to evaluate signs of return to sensibility, stun-to-bleed time, blood lactate concentration, muscle pH, drip loss, and fresh meat color to validate the head/heart electrical stunning method for small slaughter plants. Incidence of corneal reflex was not different (P> 0.05) between head/heart (93.8%) and head only (85%) stunning. Nose twitching was more common (P< 0.05) in head only (26.5%) than head/heart (5%) stunning. Head/heart stunning eliminated rhythmic breathing, natural blinking, eye tracking to moving objects, and righting reflex, which were all observed in head-only stunned pigs. Eye tracking to moving objects was observed in 40.8% of head-only stunned pigs. Blood lactate was not different (P> 0.05) between stunning methods (head only: 8.8 ± 0.7 mmol/L, head/heart: 7.8 ± 0.7 mmol/L). Stun-to-bleed time did not differ (P> 0.05; head only: 32 ± 1 s, head/heart: 33 ± 1 s). Mean time to loss of heartbeat with the head-only method was 121 ± 5 s. No heartbeat was observed with the head/heart method. Longissimus thoracis pH, color, and drip loss were not different (P> 0.05) between stunning methods. This study determined that the head/heart electrical stunning method reduces the incidence of signs of return to sensibility without significant effects on meat quality, plant operation speed, or blood lactate concentration. In addition, the head/heart method requires no capital investment for plants that are currently using the head-only method.