Electric Stunning of Pigs
Safety Tips for Workers
- The stunner operator's station must be kept dry.
- Stunning wands should be designed so that they can be
one hand. Avoid designs where the two electrodes are held
separately in each hand. These increase a shock across the chest
- The operator should wear rubber boots and stand on
- The restrainer frame and worker walkway structure should be
grounded to a perfect ground. However, the side of the restrainer
that the stunner operator can touch should be covered with
heavy insulating materials such as a plastic meat cutting
stunning methods used commercially on pigs are effective and
induce instantaneous insensibility. A minimum of 1.25 amps must be passed
through a pig's brain to reliably induce insensibility (Hoenderken, 1982).
- To produce instantaneous, painless unconsciousness, sufficient amperage
(current) must pass through the animal's brain to induce an epileptic
seizure. Insufficient amperage or a current path that fails to go through
the brain will be painful for the animal. It will feel a large electric
shock or heart attack symptoms, even though it may be paralyzed and unable
to move. When electric stunning is done correctly, the animal will feel
- There are two types of electric stunning, head only and cardiac
arrest stunning, which stops the heart. Most large plants use cardiac
arrest head to back or head to side of body stunning. It produces a still
carcass that is safer and easier to bleed. Cardiac arrest stunning
requires the use of a restraining device to prevent the animal from
falling away from the stunning wand before it receives the complete stun.
Cardiac arrest stunning kills the animal by electrocution. Head only
stunning is reversible. Pigs which are stunned with a head
only stunner must be bled within a maximum interval of 30 seconds to
prevent them from regaining consciousness. An interval of 10 to 17
seconds is recommended.
- When cardiac arrest stunning is used, one electrode must be
either the forehead or in the hollow behind the ears, and the other
electrode is placed on either the back or the side of the body. The head
electrode should not be allowed to slide back onto the neck. When head
only stunning is used, the electrodes may be either placed on the forehead
or clamped over around the sides of the head like ear muffs. Pigs should
be wetted prior to stunning. The stunning wand must be applied to the animal
for two to three seconds to stun properly. Stunners should be
equipped with a timer.
- Meat packers should use amperage, voltage and frequency settings
which will reliably induce unconsciousness. Both properly and improperly
stunned cardiac arrested animals can look similar (Gilbert and Devine,
1991). Current flow through the spine masks the epileptic seizure. If
there is any question, electrical parameters should be verified by
scientifically valid measurements.
- To prevent bloodspots in the meat and pain to the animal, the wand
must be pressed against the animal before the button is pushed. The
operator must be careful not to break and make the circuit during the
stun. This causes the animal's muscles to tense up more than once and
bloodspots may increase. Stunning wands and wiring should be checked
often for electrical continuity. A worn switch may break the circuit
enough to cause bloodspots. Electrodes must be kept clean to provide a
good electrical contact. Operators must never double stun animals or use
the stunning wand as a prod.
- Modern stunning circuits use a constant amperage design. The
amperage is set and the voltage varies with pig resistance.
Older style circuits are voltage regulated. These circuits are inferior
because they allow large amperage surges which can fracture bones and cause
bloodsplash. The distance between the head electrode and the back electrode
should not exceed 14 inches. Pig stunners should be equipped with blunt
electrodes which do not stick into the animal.
- Good example layout for pigs
- Warris et al. (1994) found that pigs were more stressed in
with single file races compared to plants where pigs were stunned in small
groups on the floor. The intensity of squealing was highly correlated with
physiological stress measurements and PSE. Electrical stunning of pigs on
the floor is most practical for abattoirs that slaughter under 240
pigs per hour. The author has observed that floor stunning often becomes
rough and sloppy at higher speeds. In larger plants, a well designed race
will produce less stress than a poor one. Weeding et al. (1993) found
that both design and staff expertise affected stress levels in pigs.
Truck loading ramp for pigs.
Pigs move more easily through a ramp
where they walk up side by side. The outer sides of the ramp are solid
and the middle partition is "see through" to promote following
Grandin, T. 1985/1986
Cardiac Arrest Stunning of Livestock and
in:M.W.Fox and L.D.Mickley (Editors)
Animal Welfare Science
Martinus Nijhoff, The Hague, The
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