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High Expansion Gas-foam: a humane agent for emergency killing of poultry?DEF McKeegan, MA Gerritzen, JM Sparrey, TGM Demmers and CM Wathes

Background

• Ongoing threat posed by Avian Influenza requires theavailability of rapid, practical and humane methods ofemergency killing for poultry

• Range of methods developed

• Considerations• Practicality

• Cost

• Availability for rapid deployment

• Disease transmission risk

• Welfare consequences

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Emergency killing methods

• Containerised Gassing Units• Flexible but birds must be handled• Slow throughput

• Whole house gassing• Birds killed in their production housing • No handling• CO2 availability?

• Ventilation Shutdown• Controversial, available only as a last resort

• Foam (in development)• Potential to use inert gases• In situ killing without sealing buildings

Foam as an emergency killing method

• Use of low expansion foam for emergency killing in the USA has been criticised on welfare grounds as its mode of operation is occlusion of the airway

• We investigated the welfare implications of application of high expansion foam, intended as a gas delivery method

• Examined in laboratory studies involving individual birds and groups, with Nitrogen and Carbon dioxide filled foam

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• Hens, broilers, ducks and turkeys

• Surgery to implant EEG electrodes then recovery

• Individually exposed to foam filled with air (control), nitrogen or carbon dioxide in a 1m3 Perspex box

• Foam introduced from above with hand held generator

• EEG and ECG continuously monitored – baseline and during exposure – via a logger worn in a lycra backpack

• Cameras to the side and below, oxygen sensors in corner of the box at 10 cm, 30 cm and 90 cm

Individual trials - methods

Telemetry/logging unit

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Hen trials – Oxygen concentrations in N2 foam Results - heart rate responses to foam in hens

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-200 -150 -100 -50 0 50 100 150 200 250

Time (s)

Hea

rt ra

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pm)

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Time (s)H

eart

rate

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Air filled foam (control) Nitrogen filled foam

F FS S S S M M

M - MotionlessS - SubmergedF – Foam start

Hen trials – Oxygen concentrations in N2 foam EEG responses to nitrogen filled foam (UK)

6.0 36.2 36.4 36.6 36.8 37.0 37.2 37.4 37.6 37.8s

375.6 375.8 376.0 376.2 376.4 376.6 376.8 377.0 377.2 377.4s

Baseline

Transitional

Transitional Suppressed Isoelectric

HensMean(± SD) 9.8 ± 2.8 30.1 ± 6.8 65.7 ± 11.5

BroilersMean(± SD) 8.3 ± 4.4 17.6 ± 3.5 46.9 ± 8.3

Time taken (s) to reach EEG phases in relation to submersion

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Transitional Suppressed Isoelectric

Broilers CO2 -2 ± 4 16 ± 2 66 ± 25

Ducks CO2 -11 ± 2 1 ± 2 58 ± 24

Turkeys CO2 -2 ± 3a 15 ± 4 60 ± 8

EEG responses to carbon dioxide filled foam (NL)

Time taken (s) to reach EEG phases in relation to submersion

Hen trials – Oxygen concentrations in N2 foam Behavioural responses to nitrogen foam

Headshakes Ataxia/loss of posture (s)

Flapping onset (s)

Flapping bouts

Flapping duration (s)

Time to motionless (s)

Hens Mean ± SD 2.0 ± 1.8 15.5 ± 3.9 17.8 ± 3.9 3.9 ± 1.4 13.7 ± 4.2 65.2 ± 10.9

Range 0 – 6 10 - 23 13 – 24 2 – 6 5 – 21 43 – 81

Broilers Mean ± SD 2.4 ± 2.1 9.2 ± 4.0 15.3 ± 4.7 3.6 ± 1.0 13.7 ± 5.5 51.4 ± 7.6

Range 0 – 7 0 – 14 10 – 23 2 – 5 6 – 20 40 – 64

T test NS P = 0.001 NS NS NS P = 0.004

Timings in relation to submersion

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Hen trials – Oxygen concentrations in N2 foam Behavioural responses to CO2 foam (NL)

Gasping(s)

Headshaking(s)

Ataxia/loss of posture (s)

Flapping onset (s)

Time to motionless (s)

Broilers 25 ± 6 23 ± 1 54 ± 16 65 ± 15 54 ± 15

Ducks 13 ± 4 10 ± 3 38 ± 10 43 ± 7 69 ± 21

Turkeys 14 ± 2 10 ± 7 47 ± 7 63 ± 19 60 ± 20

Timings (mean ± SD) in relation to foam onset

Individual bird trials – Results summary (1)

• Immersion in high expansion foam filled with nitrogen or carbon dioxide achieved a rapid and humane euthanasia, with broadly similar responses in all species

• Carbon dioxide foam was slightly faster acting, little response to immersion in air filled foam

• Behavioural responses included headshaking, loss of posture and vigorous wing flapping characteristic of anoxic death

• Mean time to loss consciousness was 18-30 s with N2 and up to 16 s with CO2

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Individual bird trials – Results summary (2)

• Foam did not occlude the airway (confirmed by PM)

• Mode of action is anoxia (regardless of gas used to make the foam), nitrogen produced more consistent foam

• Wing flapping quickly destroyed high expansion foam

• Height of foam achieved above the bird before wing flapping begins is crucial –60cm required – to retain foam covering and prevent re-exposure to air

Group trials - methods

Cameras

Foam generators Longitudinal pen

Lateral pen

• 4 trials with broilers (192-360 birds per trial), nitrogen filled foam

• 2 pen configurations (lateral or longitudinal)

• 2 stocking densities (40kg/m2 or 50kg/m2)

• 4 foam generators (achieving 42.5 m3 foam /min)

• 8 video cameras recorded the progress of foam

• In each trial, 3 instrumented birds were monitored (EEG and ECG)

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Group trials - Foam parameters

Trial 1 Trial 2 Trial 3 Trial 4

Stocking density (kg/m2) 40 40 50 50

Number of birds 192 192 240 360

Pen arrangement Lateral Longitudinal Lateral Longitudinal

Calculated foam generated (m3) 98 102 107 96

Final foam at end of run (m3) 86 96 89 86

Estimated foam destroyed (m3) 12 6 18 10

Foam destroyed (m3 per 100 birds) 6.2 3.0 7.5 3.3

Expansion rate 346:1 350:1 337:1 342:1

Group trials – ECG responses

50kg/m2

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Time (s)

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F – Foam start

S - First and last submersion

F S S

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Group trials – EEG and behavioural responses

Time to reach EEG phases* Transitional Suppressed Isoelectric

40kg / m2 Mean ± SD 5.8 ± 2.0 24.1 ± 5.8 39.8 ± 3.0

50kg / m2 Mean ± SD 4.2 ± 3.3 19.7 ± 6.5 51.7 ± 14.8

Wing flapping Flap onset (s)* Number of bouts

Total duration (s)

40Kg / m2 Mean ± SD 3.8 ± 2.3 3.2 ± 0.8 14.8 ± 5.9

50Kg / m2 Mean ± SD 5.1 ± 5.0 3.3 ± 1.7 13.9 ± 4.7

*in relation to submersion

Group trials – Results summary (1)

• The quantity and depth of foam delivered was sufficient to keep the birds covered during wing flapping - the foam front was consistently higher than 40 cm and built up to a minimum of 50-60 cm within15 seconds of submersion

• The width of the pen of birds had a greater effect on the amount of foam destroyed than the distance it had to travel over the birds - suggests that it is the width of a poultry shed that will determine the volumetric flow rate of foam

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Group trials – Results summary (2)

• The stocking density of the birds did not greatly affect foam destruction rate, but movement of the birds away from the approaching foam meant that the actual stocking density at the time of submersion was usually maximal

• Patterns of behavioural change and onset of changes in EEG characteristics closely matched those observed in individual bird trials

• Foam as deployed in these larger trials delivered a reliable and humane anoxic kill which was robust even at maximal stocking densities

• An advantage of the foam system means that large houses can be treated in sections, leaving birds in other areas unaffected

Gas filled foam – a humane agent?

• Collectively, the results show that anoxic foam has the potential to be a reliable and humane method of emergency killing for poultry

• Particular attention must be paid to foam quality and production rates must be sufficient to achieve the required foam height over birds to combat the destructive effects of wing flapping

• The method has particular advantages for systems which would not be suitable for whole house gassing

• The industry are supportive of the approach and a proposal to produce and test a full scale on-farm system in the UK (which will be available for disease outbreaks) is currently under consideration

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Acknowledgements

• Joint project by Glasgow University, RVC and Wageningen UR• Funded by Defra (UK) and Dutch Ministry of EL&I (NL)

• Livestock treatment (Frans Withoos)• Livetec (Jules Sparrey) • Ajax fire fighting equipment

Contact:

Dorothy.McKeegan@glasgow.ac.ukMarien.Gerritzen@wur.nl