MECHANICAL STUNNING of PIGS
AND SHEEP AND GAS
STUNNING/KILLING OF PIGS
DEFINITION OF STUNNING
• Stunning is any intentionally induced
process which causes loss of
consciousness and sensibility without pain
• Mechanical stunning equipment delivers
blow to the head of an animal at 60-75
m/sec, stuns animal within 5-8 ms (and
makes nerves dysfunctional).
• Speed for sensory pathways to brain is 5080ms
PURPOSE OF MECHANICAL
STUNNING
• To render animal unconscious so it does
not feel any pain (‘insensible’)
• To enable further safe and prompt killing of
an animal while it is unconscious.
• Unconsciousness means animal cannot be
aware of any peripheral stimuli, including
pain
MECHANICAL STUNNING
• Mechanical stunning requires a delivery of energy to
brain in order to affect immediate (temporary or
permanent ) dysfunction of the brain and so render
insensibility
– Delivery of that energy inside skull due to propagation of
compression-rarefaction wave in cerebral fluid
• Sources of energy when mechanical stunning is
used
- gun powder or other explosives
- compressed air pressure
EQUIPMENT = CAPTIVE BOLT STUNNING GUN
TWO KEY ELEMENTS
• ENERGY OR ENOUGH POWER
- Energy = kinetic energy that hits the brain
• CORRECT POSITION
- Position where maximum impact can be
expected
RESTRAINT OF SHEEP
PRIOR
• Restraint – same principles as in electrical
stunning
• Restrainer conveyer
• Group pen
POSITION 1
On the top of the head
in the midline position
aiming straight down
(source HSA, 2006)
POSITION 2
Behind the ridge of horns while aiming to the
base of tongue
(source HSA, 2006)
POWER
• Appropriate size of cartridges according to
the producer ‘s guidelines
POST STUNNING
•
•
•
•
•
•
•
Immediate collapse
No rhythmical breathing
Eyes wide open
No corneal reflex
Tonic phase ( 10 – 20 seconds)
Clonic phase
IF RHYTHMIC BREATHING OR KICKING are
observed immediately post stunning
MUST STUN AGAIN!!!!
RECAPITULATION VIDEO
(source HSA)
BLEEDING
• Even chance of recovery is low, sheep must be
bled as soon as possible after stunning
• Usually in first 10 seconds within the tonic phase
• It is important that all major blood vessels are
severed.
MECHANICAL STUNNING OF PIGS
• Should not be used routinely for commercial purposes
• Might be used for emergency slaughter/killing of animals
that cannot move or other emergency situations.
• Reasons……???????
• Small volume of a pig brain
• Large skull and thick frontal bones (up to 4 cm) well
protecting pig’s brain
• Vigorous and long lasting clonic phase
Source: HSA, 2006
VIGOROUS CLONIC PHASE AFTER
MECHANICAL STUNNING
CAPTIVE BOLT IN PIGS
Source: HSA, 2006
CAPTIVE BOLT STUNNING – ATTRIBUTES OF
CORRECT STUNNING.
• Correct position of gun
• Correct angle
• Proper triggering followed by hit
• Animal collapses immediately
• Absent peripheral sensitivity
• Absent corneal reflex
• Vigorous clonic phase ( very strong kicking)
• If eyelids are wide open the animal is dead
!!!!! NO RHYTHMIC BREATHING!!!!
CAPTIVE BOLT STUNNING –
INCORRECT STUNNING
• Incorrect position of stunner on skull
• Stunning device misfires or insufficient velocity:
– Wrong cartridge
– Poor gun maintenance
– Damp powder
• Animal does not collapse
• Eyes are rolled out
• Standing kicking or escape behaviour
!!!!! RHYTHMIC BREATHING!!!!
EQUIPMENT FOR MECHANICAL
STUNNING
A – Bolt B – Stop washer C – Recuperative Sleeves D – Flange Washer
,E – Flange F – Piston G – Combustion Chamber H – Breech I –
Cartridge J – Firing Block K – Hammer L – Undercut M – Trigger N –
Barrel
Stunning
equipment
- Magnum knocker
MAINTENANCE
•
•
•
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DAILY CLEANING
Clean barrel from inside and outside
Clean bolt
Clean recuperative sleeves and washers
WEEKLY MAINTENANCE
Clean expansion chamber (carbon buildup)
REGULAR SERVICING
replace sleeves, washers etc. before
efficiency is reduced
VIDEO - MAINTENANCE
GAS STUNNING/KILLING
• ADVANTAGES
- meat quality
- easy handling systems (Butina)
• DISADVANTAGES
- aversive reactions of pigs to high concentrations
of CO2 / respiratory distress
CO2 AND ITS MIXTURES
• CO2 is heavier than air therefore in
chambers (in mixtures with air or oxygen) is
usually located on the bottom of the
chamber
• Therefore principle of moving pigs on the
bottom of the pit ( gas chamber) are used
HOW DOES IT WORK
• When animal is placed into atmosphere with a
higher concentration of CO2
• CO2 replaces Oxygen in the respiratory and
circulatory system which causes acute lack of
oxygen in CNS /unconsciousness and brain death.
• Gas stun/kill is neither immediate nor induction is
without stress
• Raj and Gregory (1995) found that pigs withdrew
from an atmosphere of 90% CO2 in less than 5 sec
KEY PARAMETERS
• Concentration of CO2
- With increased concentration of the CO2 in the atmosphere,
shorter time of exposure is needed to stun an animal
- When same period of exposure applies unconsciousness
increases with the concentration of the CO2
• Time of exposure
- In practice: from 80 – 250 sec.
- EFSA recommendation : optimum exposure time of 100
sec should be mandatory for all systems.
- GONDOLA WITH PIGS MUST REACH THE BOTTOM OF
PIT – PLACE WITH HIGHEST CONCENTRATION WITHIN
30 SECONDS FROM ENTERING THE CHAMBER.
GAS STUNNING SYSTEMS
• DIP LIFT
SYSTEM
• PATER –
NOSTER
SYSTEM
MONITORING OF CO2
• Carbon dioxide concentrations should be monitored
AND DISPLAYED continuously:
A) IN PATERNOSTER - above the pig’s head while
standing, at both 1st stop position and bottom
position. At the bottom - 0.2 m above floor level of
the gondola.
B) IN A DIP LIFT at the position the gondola reaches
after 10 sec in dip-lift systems - 0.6 m above floor
level of the gondola
• A clearly audible or visible warning must be given if
the carbon dioxide concentration falls below the
required levels.
SIGNS OF UNCONSCIOUSNESS
• The stunning efficiency shall be monitored regularly
so no pigs regain consciousness during sticking or
bleeding. Signs of unconsciousness are:
• Lateral recumbency
• Absence of rhythmic breathing.
• Gagging or gasping may be present briefly.
• No convulsions present.
• Absence of spontaneous blinking of the eye.
• Corneal reflex may be present briefly in a low
frequency (<5%) of the total number of pigs,
provided that other reflexes are absent.
RETURN TO CONSCIOUSNESS
BLEEDING AND STUN TO STICK
INTERVALS
• In experiments 1 min of exposure to 80% carbon dioxide
induced unconsciousness lasting about 1 min. In another
study the recovery from exposure to 90% carbon dioxide was
approximately 60 to 90 sec.
• Basic principle is to stick as soon as possible
Time of exposure 90% (sec)
Sticking within (sec)
100
120
130
30
30
60
GOOD PRACTICE
• In dip-lift and pater-noster systems, pigs shall be exposed to
a minimum 80% carbon dioxide within 10 sec from leaving
atmospheric air.
• The carbon dioxide concentration at the bottom of the pit
shall be a minimum 90%.
• Exposure time to carbon dioxide shall be sufficient to ensure
that no pigs regain consciousness before death supervenes
through bleeding.
• A minimum exposure time, which cannot be shortened by
the personnel, appropriate to the concentration gradient in
the pit must be set.
DIP – LIFT SYSTEM
PATER-NOSTER
AUTOMATIC DRIVEWAY
SYSTEM
THE ADVANTAGES OF DRIVING
THE PIGS IN AUTOMATIC
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No contact with personnel
Low noise level
Minimal shadows
Adjustable pressure
Variable driving speed
Synchronization with CO2 stunning
system
AUTOMATIC DRIVEWAY
SYSTEM
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•
•
•
Model Butina Push Hoist Gates (PHG)
Speed forward m/s 0,25 - 0,50
Total time Sec. 62 - 39
Capacity of the handling system / pigs
pr. hour: 870 - 1380
HOW ABOUT THAT?
• Midas stunning system with three-electrode
stunning capacity 300 – 700 animals per
hour
OLD STYLE HANDLING
SYSTEMS
BUTINA SYSTEM
Questions??
THANK YOU FOR YOUR ATTENTION
Organisation mondiale
de la santé animale
World Organisation
for Animal Health
Organización Mundial
de Sanidad Animal
12 rue de Prony, 75017 Paris, France - www.oie.int – [email protected]