Agriculture Reference
In-Depth Information
problem with turkeys where, due to their wingspan, the
wings tend to hang below the level of the head. Pre-stun
shocks can be reduced by providing an insulated entry
ramp to the bath, avoiding overflow of water at the
entrance and by providing a moving belt to support the
breast of the bird so that the turkey is presented to
the stunner at an angle which raises the wings above the
level of the head.
In an attempt to calm the birds, 'hanging on' is usually
carried out in either dim (<5 lux) or blue lighting, a
breast comforting strip which rubs along and supports
each birds ventral surface as it passes is provided (com-
pulsory in the EU from 2013) and a minimum time
interval between shackling and stunning of 12 seconds
for poultry, 20 seconds for turkeys, is allowed during
which the birds may calm down. Given these parame-
ters, the shackling to stunning period should be kept as
short as possible, 1 minute for chickens and 2 minutes
for turkeys.
The height of the water bath in relation to the shack-
les, and the level of water in the bath, should be adjusted
to the size of bird to be stunned or killed so that there
is at least complete immersion of the birds' heads in
the water or preferably immersion up to the base of the
wings. Food grade salt may be added to improve the con-
ductivity of the water and sufficient voltage provided to
deliver the recommended average currents given in
Table 7.1. However, overflow from the water bath and
the addition of water to maintain levels means that the
salt concentration can drop quickly, so the initial addi-
tion of salt should not be relied upon to compensate for
deficient water bath current. It may be necessary to add
more salt or increase the voltage when the conductivity
of the water drops (Perez-Palacios and Wotton, 2006).
The poor bird welfare inherent with the need to hang
birds in an inverted position on shackles has been
addressed in a prototype system which restrains the birds
on a moving conveyer and applies an electrical stun
through dry electrodes first to the head only and then
head to body to induce cardiac arrest. A constant current
of 150 mA/50 Hz is applied for at least 1 second across the
head followed by at least 1 second across the heart. This
system may have particular benefits for heavy turkeys.
Assessment of unconsciousness in electrical
water bath stunned poultry
The most reliable indicator that a bird is properly
stunned by a low-voltage method is the electroplectic fit.
The characteristics of this condition are the neck arched
with the head directly vertical, open eyes, absence of
corneal reflex, wings arched, rigidly extended legs and
constant rapid body tremors.
When cardiac arrest is induced, these signs are shorter
lasting and they are followed by a completely limp car-
case, no breathing (absence of abdominal movements
in the vent area), loss of nictating membrane reflex
and dilated pupils. The comb reflex can also determine
whether sensibility has resumed after stunning or neck
cutting. It should be borne in mind that the absence of
rhythmic breathing is not a valid sign of unconscious-
ness in birds that have had their neck broken or severed,
for example, during neck cutting.
Although cardiac arrest is preferable from a welfare
standpoint, the use of high stunning currents is thought
to be associated with quality issues such as wing haemor-
rhage, red skin conditions including red wing tips and
pyrostyles, poor plucking, broken bones (in particular
the furculum) and ruptured blood vessels causing blood
splashing in the breast muscle.
stunning/killing poultry with controlled
atmospheres
The use of
gaseous mixtures
for the stunning of poultry
in their transport crates prior to shackling has obvious
benefits for welfare. Various concentrations of CO
2
and
argon in air have been studied experimentally. It has
been concluded that poultry do not find concentrations
of CO
2
up to 30% by volume aversive. The EFSA report
of 2006 recommends the following gas mixtures for use
in chickens:
1
Minimum of 1 minute exposure to 40% CO
2
, 30%
oxygen and 30% nitrogen, the
induction phase
, fol-
lowed by a minimum exposure to 80% CO
2
in air, the
finishing phase
or
2
Minimum of 2 minute exposure to any mixture of
argon, nitrogen or other inert gases with atmospheric
air and CO
2
, provided that the CO
2
concentration
does not exceed 30% by volume and the residual oxy-
gen does not exceed 2% by volume or
3
Minimum of 2 minute exposure to argon, nitrogen,
other inert gases or any mixture of these gases in
atmospheric air with a maximum of 2% residual oxy-
gen by volume.
Birds stunned with argon alone take twice as long to
lose sensibility as those stunned using other mixtures,
Table 7.1
Minimum recommended average current (mA)
delivered to birds in water bath stunning systems EFSA
(2004, 2006)
Frequency (Hz)
Chickens
Turkeys
Ducks and geese
Up to 200
100
250
130
200-400
150
400
400-1500
200
400
