Agriculture Reference
In-Depth Information
It has also been demonstrated that the use of tongs
with 300 V in a restrainer-conveyor resulted in superior
pig meat quality compared with automatic stunning with
680 V, the incidence of PSE being much less in the for-
mer method which also showed superior values in rela-
tion to pH, temperature, rigor mortis, bacteriological
status, etc. It is likely that these differences were due to
variations in the amperage and in the number of inter-
ruptions in the flow of the current during stunning
(Van der Wal, 1983).
Since carbon dioxide-anaesthetised pigs do not exhibit
clonic convulsions post-stunning, they are safer to handle
for the operators even when blood is being collected for
human use. It is generally accepted that carbon dioxide
produces the lowest incidence of PSE and blood splash,
and that overall the quality of meat produced is superior.
is anaesthetised and the heart put into arrest, thus cutting
off the blood supply to the brain, which suffers death
before anaesthesia ends. Research work has shown that
brain function ceased 23 seconds after this system of
stunning, whereas this time was extended to some
50 seconds with head-only stunning. The animal is, in
fact, killed, thus improving animal welfare and making
the stun-to-stick interval less important. Provided stick-
ing is performed intrathoracically within 3 minutes,
bleeding is satisfactory. A minimum current of 1.3 A
applied with a minimum of 250 V is recommended for
pigs and 1.0 A at 375 V for sheep.
In order to be fully effective, head-to-back/leg stunning
must be combined with automatic restraining systems
which prevent adverse reflex muscular movements and
the possibility of fractures as well as making the task of
shackling and bleeding easier for operatives. 'Pelt-burn' in
sheep occasionally occurs on the back with this method.
slaughter of minor species
For further detailed information, the European Food
Safety Authority (EFSA) report on the welfare aspects of
the main systems of stunning and killing applied to com-
mercially farmed deer, goats, rabbits, ostriches, ducks,
geese and quail is recommended.
Effect of stunning on meat quality
Most of the problems associated with penetrative per-
cussive stunning (captive bolt) appear to result from an
unduly long interval between stunning and sticking and/
or inadequate penetration of the bolt, resulting in blood
splashing in muscles , particularly of the diaphragm, the
abdominal wall, the intercostal muscles and the heart.
The all-too-frequent, and illegal, habit of group stun-
ning a number of animals before shackling/bleeding -
especially in sheep - is a practice that leads to this result,
the animals first 'stunned' being the ones affected. This
lesion tends to occur where there is a marked rise in arte-
rial blood pressure, the highest rates taking place in
head-only electrical stunning, where the incidence can
be markedly reduced by the adoption of a short stun-to-
stick interval.
Head-to-back/leg electrical stunning produces a very
low incidence of blood splashing, but petechiae may on
occasions occur in connective tissues and fat. High-
voltage head-only stunning in pigs sometimes results in
petechial haemorrhages throughout the loin. High-
voltage electrical stunning may also result in the fracture
of bones with associated haemorrhage into surrounding
tissue. The fracture is thought to be due to the force of
the tonic convulsion induced during and immediately
after stunning and to be reduced by increasing the fre-
quency of the sinusoidal AC from 50Hz, the norm,
upwards towards 1500 Hz. However, increasing the fre-
quency of the current has the disadvantage of reducing
the fibrillating effect on the heart. Fractures occur in the
scapula, pelvis, the neck of the femur and around the
fifth or sixth thoracic vertebrae and are much more com-
mon in pigs, which have greater muscle mass than sheep.
Slaughter of deer
The family Cervidae includes red deer, fallow deer,
muntjaks, moose, caribou and roe deer. They are often
characterised as being either 'farmed' or 'wild, but for
the purposes of considering their welfare at time of
slaughter or killing, it is more appropriate to categorise
them as domesticated, semi-domesticated or wild.
Domesticated deer may be transported in specially
adapted vehicles to abattoirs which have handling facili-
ties adapted to deal with their welfare needs. The most
common method of slaughter is percussive penetrating
captive bolt, but head-only low-voltage electrical stun-
ning and free bullet are also used.
The bolt velocity and hence the size of charge and type
of pistol will vary with different types of deer in addition
to their age and sex.
Head-only low-voltage electrical stunning requires a
minimum current of 1.0 A for fallow deer and a mini-
mum current of 1.3 A for red deer, applied across the
brain using tongs. While fallow deer show similar tonic-
clonic reactions as other domestic livestock, red deer
either exhibit a very short tonic phase or none at all.
Clonic activity characterised by violent kicking lasts
approximately 30-45 seconds in red deer and approxi-
mately 20 seconds in fallow.
The use of a free bullet to kill deer in the slaughter-
house has been used, but more frequently, it is the method
of choice for semi-domesticated or wild deer shot in the
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