Small-Scale Poultry Stunning

Small-Scale Poultry Stunning

National Center for Appropriate TechnologyFebruary 2009

Anne Fanatico, Ph.D.

Poultry are not included in Humane Slaughter ActHowever,

Birds should be stunned before slaughter because they feel pain

Electric stun is not a painful shock”, insensibility is instantaneous

Birds should be insensible to pain at the time of slaughter

Neck cut without stun, bird stays conscious for at least 15-30 secondsThis suffering is avoidable.

RestrainStun/KillBleed

Restraint/Immobilization

Position the bird for kill/stunProtect carcass quality by reducing wing flapping and convulsions

Methods•Manual•Shackles•Kill cone

Gas stun/kill generally uses a container

Humane slaughter Slaughter that occurs without causing avoidable fear, anxiety, pain, suffering, distress (Raj seminar)

StunNot required by law for poultry•Large plants: Universal (to immobilize bird and reduce carcass damage)•Small plants: Common•Small farms: RareWelfare programs require stunningBirds feel pain and should be insensible at slaughterStun method should induce immediate loss of consciousness (Raj seminar)

Stun should be longer than time interval between stun and neck cut (at least 40s)

Zero tolerance for birds entering scalder alive

Religious kill does not stun: kosher or halal

Stunning and Immobilization

Electric stunning immobilizes bird and positions it for automatic killer

Stunning also reduces massive involuntary wing flapping and muscular activity that may damage carcass and meat quality

• Electric Waterbath, group Whole body

Handheld, individual Stun knife, whole body Electrodes, head-only

• Mechanical•Penetrative captive bolt•Nonpenetrative captive bolt (concussive)•Firearm with free projectile•Maceration (only for embryos and young chicks)•Cervical dislocation

• Gas

• Atmosphere

Types of Stun/kill

ElectricalElectrical stun must be instantaneous

Head only Causes a generalized epilepsy Severe wing flapping if unrestrained (Gregory, 2004)

Whole body Exposes the body to a current generating a generalized epileptic form and, possibly, fibrillation or stopping of the heart (killing)

Currents travel through paths of least resistance (skin, breast muscle, cardiac muscle, leg muscle(abdominal fat has greatest resistivity of tissues)As a result, muscle contractions (tonic spasms and tremors) are stimulatedHeart and respiratory rates decrease and blood pressure increase (Bilgili 1992)

Majority of current may pass through body (only 20% through head) (Raj seminar)Impact on meat quality

Recoverable stun commonly used in USRegular breathing returns (signaled by return of abdominal movements in vent area)Bird should be cut and bled before recovery

Signs of effective stun•Absence of rhythmic breathing•Absence of third eyelid reflex•Constant rapid body tremors•Wings held tight against body

Signs of effective kill•Absence of rhythmic breathing•Absence of third eyelid reflex•Wings droop•Dilated pupils

Signs of ineffective stun/kill•Rhythmic breathing•Tension in neck•Ability to control head•Third eyelid reflex

Low voltage electric stun results in:

Epileptic seizure phase All or nothing threshold event; Can occur as low as 8 mA (notes) Although 45 mA needed for effective immobilization (Bilgili 1992)

Theorized that epileptic waveform are insensible to pain and are unconsciousnessHumans who have experience of grand mal or epileptic seizure report no pain

Electrical stun parameters

Impact of waveform (AC, DC constant, DC pulsed)

Impact of frequency (Hz, waveform per second) (household currents at 60 Hz)

Impact of amount of current or amps (mA) or voltage (V)

Period of time stun is applied

Electrical circuit should be in form of a closed loop

Amps do the actual stunning

Electric Water bath Stun

Causes epileptic waveformIn Europe, causes cardiac arrest

Electrical circuit passesthrough whole body

U.S.Low voltage stun used30-60 V, 20-45 mA/birdRecoverable stun

Europe High voltage stun used; stun to kill (for welfare reasons)150 V, 100 mA/bird (Bigili, 1999)Causes 90% heart fibrillationOver 120 mA can cause carcass damage (Wilkins, 1999) However carcass and meat quality issues can result from high voltage stunIncreased breast muscle hemorrhagesRed wingtipsBroken pectoral bones (clavicle, scapula)

Use of high frequency can reduce problems (increase from 60 Hz to 500 Hz) However, birds only stunned rather than killed by cardiac arrest

Use constant current rather than constant voltage (Raj seminar)

Electric Water bath Stun

Electrical Water Bath Stun Welfare Issues

Handling can be problematic: Dumping, inversion and shackling live birds Pre-stun shocks possible Inadequate stun possible Mis-stun (flock uniformity issues, insufficient feet-shackle contact (heavy scales on feet, not wetting feet-shackle contact point, wet birds (causes current to flow over surface of bird); high variation in resistivity of skull depending on thickness and density) Live birds may enter scalder; no red birds (associated with short bleed out time)

Stunning monitors (anmeter) can help insure adequate stun (Gregory, 2004)Bleed for 90 s (Bilgili 1992)

Handheld Electrical StunningStun knife

Electrical circuit passes through whole body Uses a metal grounded support (i.e. hang bird from a shackleCurrent runs through entire bird (whole body stun)Usually delivers about 200 mA, depends on setting

Problem:There are no protocols for use with animal welfare in mind

Little metering is doneTo determine volts and amps

Handheld electric stunner:Head Only

Two electrode pads on forked handsetHead-only stunDelivers 130 volts

Available in EuropeProblem: when converting to USElectricity, amps and volts may change

Air-powered

Cartridge-powered

http://www.acclesandshelvoke.co.uk/cashpoultry.htm

maximum pressure of 135psi

Captive boltStun/kill

One person can restrain and stun birdsTwo people required for adult turkeysGenerally used for euthansia

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Penetrating captive boltSevere wing flapping; may be reduced in a cone

Knocker head type

Air pressure (PSI)

Flat Broiler 110

Hen 110

Convex Broiler 120

Hen 120

Turkey (adult) 135

Turkey (poult) 60


Amount of air pressure needed for various bird types

Knocker headConvex orFlat


Position instrument at right angle to skullHold beak loosely; release grip when firing


Flat or convex knocker head



Cartridge components must be cleaned after use


Use minimum of 55 PSILarge rabbits: Increase PSI Two shots in quick successionZephyr is 99.6% effective whenused correctly

Place stun gun betweenears at top of skull

Modified nail gunCompressed air-driven,non-penetrating captivebolt to humanely stun rabbits

Captive Bolt: ConcussiveZephyr Stun Gun for Rabbits

Nonpenetrating captive bolt; concussiveBleed animal quickly before consciousness returnsNot recommended for euthanasia because animal may return to consciousness

Modified nail gun vs captive bolt gunNail gun pushes; must hold headLeaves wound size of quarter; little bleeding

Gas stunning

Large scale

Advantages: Less handling Birds can be killed in coop No inversion or shackling of live birds

Gas cart

http://www.fpmne.com/

Gas-stun

Small scale

Containerized

Gas approaches

Use argon/nitrogen with no more than 2% oxygenUse argon/nitrogen mixture with no more than 30% CO2 and no more than 2% oxygen

High levels of CO2 (above 30%) is aversive to birds; causes breathlessness; acid is produced

Anoxia (lack of oxygen) Leads to carcass convulsions after bird is unconscious (carcass damage)The use of CO2 at low levels can help reduce motor activity

Two phase approach Uses CO2 at 30% for anesthesia and then increases to 80% for euthanasia

What if you don’t have any stunning equipment?

•Cervical dislocation•Rapid decapitation(Not universally accepted as humane)(Practice with anesthetized birds; discard meat)

Spinal cord is severed

Carcass issuesWing flapping, violent muscular contractions Broken wings, poor bleeding, red discoloration (McNeal, 2003)

Meat quality issues Convulsions involving wing flapping associated with acceleration in breast muscle ATP and glycogen depletion and poor water-holding capacity

Watch cervical dislocation demonstration on Humane Slaughter Association video

Variable Neck cut Decapitation Stun, neck cut

Early (0-10 s) 1.8b 3.3a 1.2c

Intermediate (10-60 s)

3.0b 3.9a 2.0c

Late (> 60 s) 2.6a 2.4a 1.9b

Reaction scores1 = none to mild muscle quivering2 = mild wing flapping3 = moderate spasmodic body movement and full wing flapping4 = violent wing flapping and full-body movement capable of damaging carcass

Impact of stunning on body movement (McNeal 2003)

Results: Body movements that can lead to carcass damage are more violent with decapitation than neck cut; stunning reduces wing flapping and muscle contractions compared to decapitation and neck cut

Not stunning

Neck cut: Bird usually loses consciousness within 15 s, but some birds conscious for 30 s (Gregory, 2004)

Decapitation: loss of brain activity within 15 s (McNeal, 2003)

Factors to consider in stunning/not stunning

•Operator welfare

•Bird welfare

•Bleed out/carcass damage

•Meat quality

Bleeding Efficiency

At neck cut, blood shunted to organs in attempt to maintain homeostasis; only about half of the volume is lost

Bleeding efficiency depends on •Blood vessels that are severed

Ventral cut: cuts 4 blood vessels (2 carotid; 2 jugular) Bilateral cut: only cuts 2 vessels (slower bleeding)

•Size of cut•Orientation of carcass (vertical position)•Stun

Low voltage: muscle contractions force blood away from skeletal muscle towards large vessels for more efficient bleedingCardiac arrest can slow bleed out but doesn’t necessarily reduce blood

loss (Gregory)

Bleeding Efficiency

Variable Neck cut Decap Stun, neck cut

Bleed out (Newell and Shaffer 1950)

45% of total blood volume

39% of total blood volume

Source Newell and Shaffer (1950)

Meat Quality Basics

Conversion of muscle to meatBased on biochemistry

Muscle evolved for locomotionMuscle contracts, myofibrils interlock (sliding filament); cross bridges formMuscle does not die immediate at death of animalATP is required to break crossbridges of myofibrilsRigor mortis occurs because myofibril crossbridges cannot be broken afterATP used up; (until proteins start to degrade)

Meat quality factors•pH•Water-holding capacity•Texture, tenderness•Color•Nutrients•Shelf life

Impact of Stress on Meat Quality

Dark, firm, dry meat (DFD)Stress sensitive birds may exhaust glycogen stores and, after death, experience little pH reduction due to low production of lactic acid. This can lead to dark, firm, dry meat that has a high ultimate pH and is susceptible to bacterial growth and has a short shelf life.

or

Pale, soft, exudative meat (PSE)Accelerated metabolism which, when occurring in a carcass that is still warm, can lead to denaturation of protein and PSE-type meat with poor water holding capacity and a low ultimate pH.

Rate and extent of pH decline

Rate: You don’t want pH to go down too fast while muscle is hot or denaturation occurs (PSE)Degree: You don’t want the pH to be too low (it might get to the isoelectric point)You don’t want the pH too high (poor shelf life)

Electric stunning slows rigor

Documents

Small-Scale Poultry Stunning