Head-only followed by cardiac arrest electrical stunning is an effective alternative to head-only electrical stunning in pigs
Vogel, K.D., Badtram. G., Claus, J.R., Grandin, T., Turpin, S., Weyker, R.E., Voogd, E.
Department of Animal Science, Colorado State University, Fort Collins, 80523.
Journal of Animal Science. 2010. Dec 23 (Epub ahead of print)
Abstract
Many small slaughter facilities use head-only electrical stunning to render swine unconscious and insensible to pain prior to
slaughter. Head-only electrical stunning is a reversible procedure that is optimally effective for approximately 15 s following
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
two-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 to 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 /- .7 mmol/l,
head/heart: 7.8 1 .7 mmol/I). 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.
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