On-Farm Killing Of Poultry Using Gas – UK Experiences from January 2007. David Pritchard Gordon Hickman, describing mass depopulation methods, comaring these methods with the Anoxia method of using Nitrogen base gas foam. Interesting read, including nice graphics!

1. On-Farm K illing Of Poult ry
Using Gas – UK Ex perienc es
David Prit c hard
Gordon Hic k m an
23 J anuary 2007

2. Overview
Recent developments & UK experience of:
q R&D Programme of physiology of gas
mixtures
q Containerised Gassing Units (CGUs)
q Whole House Gassing (WHG)
q Foam

3. Bac k ground
q Permissible techniques for
killing birds for disease control
(WASK, schedule 9):
yDislocation of the neck (NB OIE
code)
yDecapitation
yLethal injection
yFree bullet XXX
yElectrocution
yExposure to lethal gases
yPercussion killer

4. Bac k ground - Wheelie Bins
q Use Carbon dioxide
q Welfare issues: gas, bird
monitoring, physical trauma
& crushing; smothering
q Technical issues:
ygas supply
ytemperature
q Consequently there was a perceived need for an improved
system that addressed some of the welfare and technical issues
presented by the wheelie bin system

5. R& D – Modified Bins
q Study initiated at Bristol
University - “Emergency
Killing of Poultry on Farm
using Gas Mixture”
q Led by Dr Mohan Raj
q Major objectives
yInvestigate alternatives to
CO2
yModify design of bin
yExamine rates of filling with
gas in a variety of
circumstances

6. R& D - Alt ernat ive gases
qAvailable gases:
y inert gases (argon,
nitrogen);
y inert gases + CO2;
y carbon monoxide;
y cyanide
qAversiveness of gas
mixtures
qSelected: Ar: CO2 in
an 80:20 mix
yWelfare;
ycost;
y availability;
ypracticality;
yhealth & safety

7. Conc ept Developm ent (CGU)
q Subsequent “brainstorming”
resulted in birth of the
Containerised Gassing Unit or
CGU
q Principle of ramping up usual
procedures during crisis
y Use available catching teams
y Use available Poultry transport
module and crates
q Principle of simple robust
systems
y Gas tight container
y Supply of argon/CO2
y Monitoring equipment - Oxygen
meter

8. Cont ainerised Gassing Unit
q The containerised gassing units consist of a gas
- tight steel (3mm thick) container (1.5m W x
3.0m L x 1.5 H = 6.75m3)
q A number of standard poultry transport modules
q A supply of a 80% argon and 20% carbon
dioxide gas mix.

9. q2 CGUs and 6
modules stored on an
articulated trailer for
rapid response
q Gas sourced
separately
qBoth deployed in less
than 24 hours
q50 CGUs in total
Port able Syst em for Rapid
Deploym ent

10. q The container is pre-fitted
with gas pipe work and
diffusers to disperse gas
and reduce noise and are
secured to the metal
container.
q Each container comes
with two gas regulators
and a manifold
q For transport these are
securely attached to
inside back panel of CGU

11. q A rack full of
individual gas
cylinders
qManifold system and
gas regulators

12. q One standard chicken
transport module
containing poultry are
placed inside the CGU
using a forklift
q Capacity depends on
size of bird
q 12 drawers each with 25
birds = 300 chickens per
unit

13. q The door is shut and secured.
q The gas supply is turned on and
maintained at 3 bar delivery
pressure for up to three minutes
or until a residual oxygen of 5%
by volume is registered in the
oxygen analyser.
q The birds are held in the gas
mixture for up to five minutes
from the moment of turning the
gas on or until wing flapping has
stopped (as determined from
listening to the sound)
Oxygen
analyser

14. q A forklift is used to remove
the module full of birds and
it is placed in atmospheric
air.
q Each draw is pulled out
and examined to check
that there are no survivors.

15. qAfter checking for
survivors,
carcases are
sprayed with
disinfectant

16. q The dead birds are
emptied into bags or
direct into leak-proof
lorries
q Self-emptying modules
can be used to minimise
manual handling

17. Each module will hold about 300 chickens (2 kg)
q CGU can be filled in 2 minutes and an additional 30
seconds exposure to gas mixture will effectively kill the
birds
q Operating with two metal containers on a farm would
therefore facilitate killing 600 chickens in 5 minutes
q Allowing an interval of 5 minutes between each cycle,
for the purpose of unloading and reloading metal
containers with modules, would in theory allow the
killing 6,000 birds per hour.
Work ing Assum pt ions

18. q For planning purposes a maximum
throughput of 4,000 birds per hour is used.
q Incidentally, a catching team of 5 people can
also work at the rate of crating 6,000 birds
per hour
q Therefore, one catching team could supply
birds to operate two containers on each
farm.
Work ing Assum pt ions

19. Field ex perienc e w it h CGUs
qOver 120 staff trained using DVD, SOP and
practical course
qUsed on three farms in Norfolk LPAI outbreak
with about 48,700 birds killed in less than 48
hours
qUsed for East Lothian NDV outbreak for 12745
birds ( partridge, quail, pheasant chicken)
qPlanned throughput achieved with safe
operation and humane kill
qPositive media coverage

20. Cont ainerised Gassing Unit s
Strengths
q Used in last 2 UK poultry disease outbreaks
q Modest cost
q Proven technique
q Humane – non-aversive gas mix
q Flexible
Weakness
q Individual birds need to be handled
q H&S associated with use of gas
q Moderate throughput
Uses
q Medium sized units (10 - 20,000 birds)
q Free range and Caged units

21. Whole House Gassing Trial
qBirds being culled for disease reasons
qNE England October 2006
qUsing liquid Carbon dioxide direct
injection into the house
q to kill 13,000 chicken poults

22. Rec ording
probes
for gas &
Tem perat ure
Preparat ion
of house
House
m easured
Lengt h 30 m
Widt h 12 m
Height t o
ridge 4m
Plac ing
Biosec urit y and
Safet y Barriers

23. Preparat ion
Trailer with variable
height assembly for lance
fitted with high pressure
hose
( pressure over 5 bar)
Preparation of site and
presite briefing
Closed inlet flaps in side
walls immediately prior
to gas delivery

24. Delivery lanc e
Lance placed at
approximately
1.5 meters above floor
End of lance cut at 30 0
to direct gas to roof of
house
Temperature probe in
situ

25. Video Monit oring using IR
c am eras

26. Gas delivery equipm ent and st aff

27. Gas m onit oring
Personal Carbon dioxide meter Continuous gas monitor

28. Perimeter security
Gas Delivery t o House
4 Tons of Liquid CO2
delivered in 4 minutes
Housed closed for 1
hour

29. Safet y Chec k s
Post gassing
Operatives work
in pairs for safety
Engineers using
Breathing apparatus
used to check gas levels
to certify safe entry for
vet to check birds are
killed

30. Indic at ors of hum ane k ill
observed post c ull
qDistribution of birds e.g. clumping or
stacking of birds indicating signs of panic
or suffocation
qPosition of birds post cull – lateral
recumbency or supine or ventral
qExternal signs on birds of injury or dam
qSigns of convulsions e.g. disturbed litter

31. Dist ribut ion of birds post k ill

32. Ventral recumbency
Lateral recumbency
No signs of
convulsions

33. Com paring dist ribut ion before
and aft er gas delivery
Before - showing
free dispersion
After - showing a
small amount of
clumping

34. Post k ill dist ribut ion
qBarrier placed half way
down house to limit
clumping
qSome clumping was
seen around barrier
Indicating that birds
did move away from
source of gas

35. Liquid Carbon diox ide k illing
of poult s - Conc lusions
qGood preparation of house – removal of
furniture and feeding systems and barrier put in
place
qEffective delivery systems 4 minutes to 50%
CO2 at 1.5 meters high
qNo evidence of poor welfare such as injury,
suffocation, or convulsions
qSome evidence of movement from the incoming
gas stream
qHumane acceptable system of killing small
chickens

36. Gassing – w hole
house
Strengths
q Widely used in Holland and Canada
q Live birds do not need to be handled
q Large numbers can be killed quickly
q Humane
Weakness
q Need technical support
q H&S associated with use of gas
q Large quantity of gas required
q Limited range of houses suitable ?
q Uses
q Large broiler units
q Some caged units?

37. Low Densit y Foam For K illing
Poult ry On-Farm
Using nit rogen or sim ilar
anox ic gas m ix t ure

38. Low densit y foam For K illing
Poult ry On-Farm
q Still under development
qDetails subject to commercial confidentiality
q Low density foam as a carrier for anoxic gas
q Death by exposure to anoxic gas mixture and
not by physical obstruction of trachea/lungs
q Trials using nitrogen and carbon dioxide
q Trials using small buildings
q Laboratory scale trials with animals

39. Foam generat ion
q Low density foam
produced using standard
fire fighting foam
generator from surfactant
and water
q Instead of air, anoxic gas
is used to create bubbles
q Surfactant specification
and quantity is the key
q Fragile dry foam needed
not not strong wet foam

40. Liquid Nit rogen
& Vaporiser
qNitrogen is cheaper,
readily available and
non-aversive
qNitrogen has a
higher boiling point
and can be
vaporised more
easily than carbon
dioxide

41. Gas Delivery
q Gas (not liquid)
delivered to foam
generator at close to
ambient temperature
qFoam rapidly fills
building

42. Princ iples
q Foam surfactant must
be robust enough to
hold gas and fill building
to required height
BUT
q Fragile enough so that
bird movement breaks
bubble and releases
gas
q accepted by the birds
q Further development required before it can be considered for
practical on-farm use

43. Ac k now ledgem ent s
Thank s t o
qBristol University
qRoslin Institute
qSilsoe Research Institute and University of
London
qCommercial partners and poultry farmers
qState veterinary service staff who developed
practical training and lead field operations
qDefra colleagues in AWD