Agriculture Reference
In-Depth Information
Pig movement and restraint
One of the greatest problems in delivering animals to the
point of slaughter is presented by the necessity for pigs to
be stunned by high-voltage electric current to arrive at
the point of stunning continuously at a rate of several
hundred/hour, in single file, and to become confined in a
'V'-shaped restrainer. With their feet off the floor, ani-
mals are less likely to attempt to struggle and be injured.
Restrainers which support the animal on the chest have
been shown to be less stressful for pigs than 'V'-shaped
restrainers. Pigs prefer to move as a group, with their
comrades on either side. They resent being forced into
single file. The answer, to some extent, has been to utilise
a
curved double race
where the pig can see his comrades
moving along beside him, but there still comes a point in
most cases where the double race must feed into one sin-
gle restrainer. The single-file chute should be at least 6 m
long to achieve continuous flow, but no more than 10.5 m
long, to keep the pigs moving without excessive goading.
A common alternative for high line speeds is to use
a
gas stunning system
which allows several pigs to be
stunned simultaneously. The pigs may be allowed to move
along a passageway with the group size gradually decreas-
ing as pigs progress at different speeds, until the required
number is attained. This group, usually of about five or six
pigs, is moved into a small pen which descends into the
gaseous environment where stunning occurs. Line speeds
of 800 pigs/hour can be accommodated by this system.
The effect on pigs of immediate pre-slaughter stress,
as measured by post-mortem blood biochemistry and
meat quality, has been studied by Warriss, Brown and
Adams (1994). They concluded that these subjective
assessments of the stress suffered by pigs correlated well
with objective measures, specifically the sound level
immediately before stunning, and that as expected
higher stress levels were associated with poorer meat
quality. They confirmed that the confinement and
restraint associated with race-restrainers were stressful
to the animals, and that the use of
electric goads
to coerce
pigs to move along these systems, particularly at high
line speeds, increased the levels of stress.
animals concerned and the operations that they carry
out. Related operations are defined as handling, restrain-
ing, stunning, assessment of effective stunning, shackling
or hoisting of live animals and bleeding live animals.
Farm animals may be stunned utilising the following:
1
Percussive blow to the head
2
Penetrative captive bolt
3
Non-penetrative captive bolt
4
Electrical stunning
5
Exposure to gas mixtures
They may be killed using the following:
1
Firearm with free projectile
2
Electrocution
3
Exposure to gas mixtures
Assessment of unconsciousness at slaughter
The nervous system, composed of the brain and spinal
cord (central nervous system), and the peripheral nerves,
is the important control and communication system of
the body. The brain, consisting of two cerebral hemi-
spheres, cerebellum and medulla oblongata, is responsi-
ble for coordinating all the activities necessary for the
maintenance of life. Situated in the bony cranial cavity, to
which it closely conforms, it contains all the vital centres
controlling the body's many activities.
The
waking state
, or
state of consciousness
, has been
described as 'a dynamic equilibrium between the activa-
tion of cerebral neuronal networks maintained by the
incessant impact of innumerable ascendant and associa-
tive impulses and the cumulative functional depression
resulting from the very continuity of this state of excita-
tion' (Bremner, 1954). Consciousness involves an aware-
ness of the environment and the ability to appreciate pain.
In the act of slaughter, it is essential that a state of
unconsciousness
or
insensibility
be
instantaneously
pro-
duced to ensure total freedom from pain, this being
further ensured by immediate exsanguination. Where
cardiac arrest
has been created, there is an almost imme-
diate insensibility which is
permanent
. The discovery
that adequate bleeding ensues despite cardiac dysfunc-
tion in this method makes this a most important devel-
opment in the slaughter of animals. It had been always
thought that a beating heart was necessary for proper
bleeding, but this has been discounted, provided sticking
is performed within 3 minutes of cardiac arrest.
The
time taken to reach insensibility
due to exsanguina-
tion depends upon the technique utilised in sticking, the
species, the age of the animal, whether the carcase is sus-
pended or recumbent and the method of pre-stunning
used. Based on electroencephalographic data, sheep have
been shown to achieve 'brain death' in 2-7 seconds, pigs in
The slaughtering process
In the past, all too often, the task of stunning was given to
untrained individuals. It cannot be emphasised too
strongly that,
in addition to the important matter of animal
welfare, proper stunning/killing plays a significant part in
preventing injuries to staff engaged in the subsequent
shackling and bleeding processes
. EU Council Regulation
1099/2009 requires those involved in the killing of ani-
mals and 'related operations' to be trained and receive
certificates of competence relevant for the categories of
