Transcript MR - - Red Meat pptx

Principles of Restraining,
Stunning and Slaughtering of Red
Meat Species, and Critical Points
in these Processes
Mohan Raj
BVSc, MVSc, PhD
School of Veterinary Sciences
University of Bristol
Langford BS40 5DU
United Kingdom
[email protected]
Critical Points - Why?
Slaughter involves conversion of conscious
farm animals into human food
Animals remain sentient until
unconsciousness is induced by stunning
Unconscious animals have capacity to regain
consciousness until death is induced via
blood loss at slaughter
Restraining
• Main purpose is to facilitate effective
stunning
• Method should be appropriate for species
and size of animals and stunning methods
• Severity of restraint should be kept to the
minimum
• Duration should be as short as possible
Restraining Methods
• Stunning pens
– cattle
• ‘V’ type
– Sheep and pigs
• Band
– Cattle, sheep, pigs
Stunning
Method should be
• Appropriate for species
• Size of animals
• Throughput rate
• Appropriate for expected stun-to-stick (bleed
out) interval
• Appropriate for blood vessels cut at slaughter
Stun animals only when shackling, hoisting and
bleeding can commence without delay
Slaughter
Method should be
• Appropriate for species
• Throughput rate
– Faster bleed out – rapid onset of death – higher
throughput
• Appropriate for expected stun-to-stick
(bleed out) interval
• Bleed out time (duration of bleeding)
Stun-to-stick interval - general
As soon as possible
–Cattle = 60 seconds
–Sheep, goat and pigs = ideally 15
seconds, within 25 seconds
Stop blood supply to the brain
Longer stun-to-stick intervals for
irreversible stunning methods
Recovery of consciousness –
probable causes
• Delayed bleeding (long stun-to-stick interval,
e.g. longer than 60s in cattle)
• Poor bleeding
– Cutting veins rather than arteries
– Blood clot
– Constriction of vascular muscles
Re-stun animals showing signs of recovery
– return of rhythmic breathing
Back-up stunner
Main Stunning Methods
• Mechanical
– penetrating and non-penetrating captive bolts
– Free bullets are rarely used in slaughterhouses
• Electrical
– Head only or head-to-body
• Gas mixtures
– Carbon dioxide, nitrogen, argon or mixtures
Mechanical
Penetrating captive bolt
Non-penetrating captive bolt
Captive bolt stunners (e.g.)
Different bolt
lengths
available to suit
different
species
Captive bolt stunning
Critical Points
•
•
•
•
•
Gun
Cartridge
Shooting position
Stun-to-stick or bleed interval
Blood vessels cut at slaughter
Gun and Cartridge
Gun
• Appropriate for the species and size of animals
• Maintained and used according to
manufacturers’ instructions
Cartridge
• Appropriate for the species (e.g. colour coded)
• Stored properly - keep dry
– Avoid high humidity / dampness
Captive Bolt Parameters
•
•
•
•
•
Diameter
Penetration depth
Velocity
Fired perpendicular (90o) to the skull bone
Ensure bolt is completely retracted into the
barrel before using
– Clean thoroughly and replace parts, if necessary
Shooting positions
Induce concussion and / or brain damage
Perpendicular or
90o to the skull
Be aware of
sinuses in large
boars and sows
Pointing
towards
mouth
Pointing
towards throat
Source: EFSA 2004 report
CB stunning cattle
Source: Temple Grandin
CBS – severity of brain damage
Good stun
Source: Temple Grandin
Poor stun
Inadequate stunning
– frequent causes
• Poor maintenance of gun and cartridge
• Inappropriate shooting position
• Rim of the bolt is blunt or disfigured
Normal
Blunt
Disfigured
Electrical stunning methods
• Head-only
–Electrodes should span the brain
• Head-to-body
–Electrodes should span the brain and
heart
Electrical stunning - sheep
Source:
Humane
Slaughter
Association
Wetting of wool helps to
improve electrical contact and
achieve effective stunning
Electrical stunning - sheep
Manual
Source: Temple Grandin
Electrical stunning - pigs
Manual or automatic
Electrode positions
– applied during manual stunning of pigs
Electrical stunning
Control Points
•
•
•
•
Stunner & electrodes
Stunning parameters
Stun-to-stick or bleed interval
Blood vessels cut at slaughter
Stunner & electrodes
Bad
Good
Source: Dr. Martin von Wenzlawowicz
BSI, Postfach 1469, Germany
Stunning Electrodes
• Should be appropriate for the species
and size of animals
• Should have good electrical conductivity
– Minimum electrical resistance
• Avoid carbon build-up
– Use wire brush to clean frequently during use
Stunners
• Out put
–Constant voltage stunners
–Constant voltage – constant current
stunners
–Variable voltage – constant current
stunners
Constant voltage – slow rise time
Note: time to reach maximum intended current (red) is slow, as the voltage remains the same
(blue) at 300V
Constant voltage – quicker rise time
Note: shorter time to reach maximum intended current (red), as the voltage remains the
same (blue) at 350V
Constant current – variable voltage
Note:
Amplitude of
current remains
(lower trace)
but initial
voltage varies
(upper trace)
Electrical stunning - parameters
• Waveform of current
– Alternating current (AC)
– Pulsed direct current (DC)
• Frequency of current (Hz)
– 50 to 1500Hz
• Amount of voltage (V) & current (Amp)
– Depends upon species and method
Electrical Waveforms (e.g)
Sine and square wave alternating
currents (AC)
Ask manufacturers’ for details
Pulsed direct current (pDC)
SW – AC frequency (Hz)
Frequency Hz
Current (A)
0.2
800Hz
0
600Hz
Period ms
200
5.00
400
2.50
600
1.67
800
1.25
1000
1.00
1200
0.83
1400
0.71
400Hz
200Hz
0.2
0
1
2
3
Period in milliseconds (ms=1000 / Hz)
4
5
pDC frequency (Hz)
Frequency
Hz
Current (A)
0.2
200Hz
800Hz
0
Period ms
200
5.00
800
1.25
1400
0.71
1400Hz
0.2
0
1
2
3
Period in milliseconds (1000 / Hz)
4
5
Effect of applied voltage on
electrical impedance
Defra (UK) funded project MH0110 & MH0111.
Effect of applied pressure on
current profile
Defra (UK) funded project MH0110 & MH0111.
Manual error (e.g.)
Current profiles
Manual stunning is more
variable than automatic
stunning
N.G. Gregory
Gas mixtures
• Used for pigs (poultry)
• Eliminates need for restraint
– group stunning in pigs
• Killing is better than stunning
– Eliminates chances of recovery
– Stun-to-stick interval is not critical
– Reduces pressure on personnel
Gas mixture - basics
• Rate of induction of unconsciousness is
related to concentration of gas
– Low concentrations require long exposure times
• Duration of unconsciousness is related to gas
concentration and duration of exposure
• Prolonged exposure to high concentrations
result in irreversible stun
– death in some animals
Gas stunned pigs
Completely relaxed carcasses
Source: Temple Grandin
Gas stunning
• Ensure smooth entry and passage of
animals through the system
• No bunching or grouping of animals
• Gas concentrations monitored and
maintained during exposure
• Visible and audible alarm systems
• Calibrate gas monitors
Loading / stunning systems for pigs
Single race
loading system
Source: Temple Grandin
Low stress group loading /
stunning system
Gas stunning
• Interval between end of exposure to gas
and bleeding last animal in a group
should be appropriate and adequate to
prevent return of consciousness
• Provision to monitor and deal with
recovery of consciousness
• Back up stunners
Literature
• Safety and maintenance of electrical stunning equipment:
http://www.hsa.org.uk/Resources/Publications/Technical%20Notes/TN5.pdf
• Stun-to-stick time:
http://www.hsa.org.uk/Resources/Publications/Technical%20Notes/TN17.pdf
• Wotton, S.B. & O’Callaghan, M. 2002. Electrical stunning of pigs: the effect of
applied voltage on impedance to current flow and the operation of a fail-safe
device. Meat Science, 60: 203-208.
• Electrical stunning of sheep and pigs – a video presentation by Dr, Grandin:
http://www.youtube.com/watch?v=-FEUfkmJQuA
• Visit www.grandin.com
Thank you