Preparation of livestock
for slaughter
At the time of
slaughter, animals should be healthy and physiologically normal. Slaughter
animals should be adequately rested. They should be rested, preferably
overnight, particularly if they have travelled for some times over long
distances. However, pigs and poultry are usually slaughtered on arrival as time
and distances travelled are relatively short and holding in pens is stressful
for them. Animals should be watered during holding and can be fed, if required.
The holding period allows for injured and victimized animals to be identified
and for sick animals to be quarantined.
Restraint devices
It is very important
that slaughter animals should be properly restrained before stunning or
bleeding. This is to ensure stability of the animal so that the stunning
operation can be carried out accurately and properly. Different types of
restraints are appropriate for different species:
Cattle
A stunning box is the
most common method of restraining cattle. The size of the box should be just
wide enough to prevent the animal from turning around, and so be difficult to
stun. The floor of the box should be non-slip. A simple neck crush used by
farmers to restrain cattle for weighing is suitable for small-scale operations.
Restraining tame cattle outside the stunning box by securing the head in a
halter and then pulling the rope through a metal ring in a concrete floor is
effective. It is recommended that this operator should be positioned behind
protective steel bar.
Sheep/goats
A properly constructed
metal stunning box is appropriate. However, they can be restrained manually
quite satisfactorily.
Pigs
A stunning box is
suitable for pigs. Putting a few pigs in a small room is suitable but only for
electrical stunning. On no account should pigs be restrained manually.
Poultry
Chickens are shackled by
their legs onto a conveyor line. This must be done gently to avoid injury and
stress. In a small slaughterhouse, birds can be placed headfirst in cones.
Ostriches
These are temperamental
animals, and because they will kick, they must be securely restrained. This can
be done by leading them into a padded V-shaped pen, with the head facing the
apex of the pen. Also the feet can be clamped immediately after electrical
stunning has begun.
Animals should never be
left standing for a prolonged period in a restraint device and must be stunned
immediately after being secured. The operator must be adequately trained and
supervised. In some countries, people who handle and stun animals have to be
trained and licensed.
Methods of stunning
It is desirable to
render an animal unconscious before it is slaughtered in order to eliminate
pain, discomfort and stress from the procedure. In some circumstances,
traditional slaughter may be exempt from pre-slaughter stunning. Whatever the
stunning method, the animal should be rendered unconscious for long enough so
that bleeding results in enough loss of blood to cause death from lack of
oxygen to the brain. In other words, death should occur before the animal would
have regained consciousness after stunning, had bleeding not taken place. There
are three main technologies used to effect stunning-Percussion, Electrical and
Gas. Only the first two are commonly used in developing countries.
Percussion stunning
Captive bolt
This method works on the
principle of a gun and fires a blank cartridge and it propels a short bolt from
the barrel. The bolt penetrates the skull bone and produces concussion by
damaging the brain or increasing intracranial pressure, causing bruising of the
brain. The captive bolt is perhaps the most versatile stunning instrument as it
is suitable for use on cattle, pigs, sheep and goats as well as horses and
camels, and can be used anywhere in the world.
For effective stunning,
it is important that the operator is well trained in its use of the stunning
gun. If the operator becomes fatigued, accuracy of stunning is reduced, so in
large plants, rotation of two stunners is recommended. Stunning of bigger pigs
may require a stronger cartridge, as the sinus cavities of the skull are
larger. Large bulls have a bony ridge in the forehead and penetration may be
more difficult, requiring off-centre aim. A captive bolt gun
is not suitable for stunning ostriches. Their brain is small and
lobulated, and the bolt does not produce proper concussion.
Gunshot
In circumstances where
animals are too fractious to be handled in the normal way, such as when they
cannot be loaded on the farm or led into the stunning restraint, gunshot with a
free, soft-nosed bullet is effective. A 22-calibre bullet is sufficient for
most animals. Shooting with a free bullet can be dangerous to operators.
This method of stunning is
well suited for pigs, sheep or goats, poultry and ostriches. Electrical
stunning induces electroplectic shock or epileptic state in the brain. This
state should last for long enough for bleeding to be carried out so that the
animal dies from cerebral anoxia. A low voltage alternating electric current is
applied by means of two electrodes, which are placed on either side of the
brain using tongs. Since the brain of animals is small, the electrodes should
be accurately and firmly placed high up on the sides of the head in sheep,
goats, pigs and ostriches.
Ostriches should be
stunned only electrically. The tongs are placed either at the sides of the head
below and behind the eye or above and below the head. Poultry can be stunned
electrically using a manually operated device or using an automatic water bath.
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