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8/9/2019 Methods for the euthanasia of dogs and cats- English.pdf
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Methods or the euthanasiao dogs and cats: comparisonand recommendations
World Society or the Protection o Animals
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FOREWORD
This document aims to provide guidance on theeuthanasia o dogs and cats by identiying methodsconsidered humane and methods that might
compromise animal welare.
The euthanasia o companion animals is a muchdebated issue or animal welare organisations aroundthe world. Opinions are diverse and are oten inuencedby local situations and cultural backgrounds.
The decision to euthanase an animal is a complexethical matter involving many actors, and a detaileddiscussion o the subject is beyond the scope o this
document. As an animal welare organisation, it is ourobligation to ensure that when the decision to euthanaseis taken the methods used are truly humane andadministered by responsible and appropriately trainedindividuals.
Methods o euthanasia, scientifc knowledge andopinions evolve over time; this overview is based oncurrent scientifc evidence and will be subject to review.
Author: Louisa Tasker, MSc, BSc (Hons.)
Editor: Companion Animals Unit, World Society or the Protection o Animals
World Society or the Protection o Animals89 Albert Embankment
London SE1 7TP
T: +44 (0)20 7557 5000
F: + 44 (0)20 7703 0208
W: wspa-international.org
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CONTENTS
INTRODUCTION 4
Criteria or euthanasia 4
Reasons or euthanasia 4
Personnel and training 4
Signs o pain and distress 4Confrmation o death 5
Carcass disposal 5
Proessional and sympathetic conduct 5
METHODS FOR THE
EUTHANASIA OF
DOGS AND CATS 6
Summary table o methods:
Recommended 7
Acceptable 7
Conditionally acceptable 8Not acceptable 10
PRE-EUTHANASIA DRUGS 13
Tranquillisers 13
Sedatives 13
Immobilisers 13
Anaesthetics 14
Combinations o pre-euthanasia drugs 14
DISCUSSION OF
EUTHANASIA
METHODS 15
Non-inhalant, injectablepharmaceutical agents 15
Barbiturates 15Other intravenous anaesthetics 16
T61 16Potassium chloride (KCI) 16Magnesium sulphate (MgSO4) 17
Chloral hydrate (CH) 17Inhalant agents (gas mixtures) 17
General considerations 17
Anaesthetic gases 17Nitrogen or nitrogen/argon mixtures 18Carbon dioxide (CO2) 18
Carbon monoxide (CO) 19
Nitrous oxide (N20) 19Ether 19
Physical methods 20
General considerations 20Shooting using a ree bullet 20
Captive bolt 20Electrocution 20Decompression 20
Hanging 21Drowning 21
Poisons 21
General considerations 21Strychnine 21
Cyanide 21
REFERENCES 22
ANNEX 1:Dosages and routes o
administration o agents
or euthanasia o dogs and cats 23
ANNEX 2:Guidelines on the intravenous
injection o Pentobarbitone or
the euthanasia o dogs and cats 25
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INTRODUCTION
Criteria or euthanasia
The term euthanasia comes rom the Greek eumeaning good and thanatos meaning death, literallytranslated it means good death. There are our
primary criteria that ensure death caused by methodso euthanasia is humane (Beaver et al., 2001). Themethod must:
1 Be painless
2 Achieve rapid unconsciousness ollowed by death3 Minimise animal ear and distress4 Be reliable and irreversible
To meet these criteria, the method should take intoaccount the species, age and health o the animal. Inaddition the method should be simple to administer,sae or the operator, as aesthetically acceptable to the
operator as possible, and preerably require small doseso any chemicals used.
Reasons or euthanasia
A decision to euthanase an animal is a complex ethical
matter involving many actors, and a detailed discussiono the subject is beyond the scope o this document.The World Society or the Protection o Animals (WSPA)
believes euthanasia is acceptable and necessary whenan animal is suering due to an incurable illness orinjury, or when an animal presents a signicant risk to
human health and saety or the saety o other animals,through disease or aggressive behaviour.
It is advisable or WSPA member societies, which mayhave cause to euthanase animals in their care, to adoptan agreed euthanasia protocol that clearly outlines the
reasons or euthanasia and the acceptable methods.
WSPA does not condone the mass destruction odogs and cats as a population control measure.Successul control o dog and cat populations requiresa coordinated strategy that has been agreed by all
stakeholders and includes:
Legislation with eective enorcement Registration coupled with a dependable method o
identication or dogs and cats Reproduction control Measures to reduce the availability o dogs and cats
through the control o breeders, pet-shops and othersales outlets
Education o owners or guardians so that they act as
responsible carers or their animals
Even when these components are in place, WSPAreluctantly accepts that there are circumstances when
the euthanasia o healthy animals is required, orexample in the case o animals that cannot be rehomed,or to avoid overcrowding in shelters that wouldcompromise the welare o animals being held there.
WSPA rmly believes that in all situations wheneuthanasia is deemed necessary, the methods adopted
should meet all our o the criteria listed at the beginningo this introduction, and hence be truly humane.
Personnel and training
All methods o euthanasia have the potential to bepoorly perormed i operators are untrained andunsupported. Consequently, it is essential that
operators are provided with suitable training, includinga period o initial tuition with assessment o prociency,ollowed by continuous monitoring o skills and ability,
as well as access to emotional support.
The initial period o instruction should, without
exception, include training in both the technical aspectso the methods to be used and the recognition osigns o animal distress. Following the instruction,
operators should understand the mechanism bywhich that particular method o euthanasia causesunconsciousness and death. They should also receive
direction and practical training in the careul handlingrequired to prevent distress in the animals they will berestraining or euthanasia. It is essential that operators
are taught to recognise the species-typical behaviourand physiological responses that indicate an animal isexperiencing ear, distress, pain or anxiety, and how to
take immediate action to alleviate these states shouldthey be observed.
Signs o pain and distress
The ollowing behaviours or physiological responses
may be signs o pain and distress:
Aggression towards humans or redirected towards selor inanimate objects e.g. snapping, biting, growling,
scratchingVocalisation whining, whimpering, high pitchedbarking, howling, or growling in dogs, hissing or yowling
in catsAttempting to escape or withdraw rom the situationStruggling
Panting
Hyperventilating
Salivating
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Pupils becoming dilated
Pilo-erection (hair standing on end)Increased heart rate (tachycardia)Shivering, muscle tremors and spasms; these may alsoresult rom refex skeletal muscular contractionsImmobility or reezing (the animal becomes tense andstops moving, but remains conscious and aware o thesituation)UrinationDeecation
Anal sacs are emptied (oul smelling liquid isevacuated)
Confrmation o death
All operators perorming euthanasia should be able toidentiy when death has occurred. Indicators include:
Nomovementofthechest/Nosignsofrespiration
The animals chest has stopped moving up anddown indicating that it has stopped breathing.DO NOT rely on this sign alone as the animals
heart may continue to beat or some time ater it
has stopped breathing
Noheartbeat
Check or this with a stethoscope or by palpating
the animals chest wall.
Nopulse
Check or this by palpation over the medialaspect o the animals hind limb.Not always easy to locate in small animals
Lossofcolourfromthemucousmembranesinthe
animals mouth
Mucous membranes become pale and there is no
capillary rell i pressure is applied. With time themucous membrane becomes dry and sticky.Capillary refll is requently still evident or
prolonged periods ater an animal has died
Cornealreex(blinkreex)islost
The corneal refex is normally elicited when the
eyeball is touched. Ater death, the animals eyesremain open and the lids do not move when touched.
Glazingoftheeyes
This occurs rapidly ater death. The cornea loses its
clear, moist appearance and becomes opaque, dryand wrinkled.
Rigormortis
I death cannot be confrmed by a veterinary
surgeon, or there is any doubt, operators should
wait until rigor mortis has set in beore disposing o
the animals carcass.
Carcass disposal
Noanimalshouldbedisposedofuntildeathisveried
Disposalshouldtakeintoaccountregulations,
disease control and drug residues
Once death has been conrmed the animal shouldbe disposed o in accordance with the local and/ornational regulations. These rules should be obtained
rom the local municipality or relevant animal health/environment departments in advance and all operatorsshould comply with the necessary procedures.
This is especially important or disease control.Moreover, many o the injectable agents used oreuthanasia may leave residues in animal carcasses.
These drug residues may pose a threat to other
animals in the event that the carcass is eaten andmay cause localised contamination upon carcass
decomposition.
Suspectrabiescasesrequirecautioushandlingand
compliance with reporting regulations
Special precautions should be taken when handlingthe carcass o any animal suspected o carrying
rabies, including the use o protective clothing:gloves, overalls, eye goggles and protective shoes.
The carcass should be sealed in a plastic bag, asthe rabies virus can remain active or some timeater death. The external suraces o the carcass can
remain inective or several hours ater death, andthe internal organs can remain inective or severalweeks depending upon environmental temperature,
so burial is not recommended. National or localregulations may require that the carcass, head ora sample o brain tissue are sent to a public health
authority laboratory or testing and surveillance.
Proessional and sympathetic conduct
All operators need to show proessionalism and respector animal welare, or the value o animal lie, and
or other people involved. The degree o distress thatoperators and other people experience when euthanasia
is perormed will be aected by their culture, beliesand the community in which they live.
Operators should be emotionally supported and trained
to develop coping mechanisms to deal with this stress.This is important or many reasons, including the riskthat dissatised personnel may become careless whenhandling animals and performing euthanasia. Ensuring that
the methods used are humane can also help to reduce the
distress experienced by operators and other people.
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METHO
DSFOR
THEEUTHANASIAOFDOGSAND
CATS
The ollowing pages assess the methods o euthanasiain current use, in terms o the eects on the animal andadditional inormation regarding usage. The methods aredivided into the ollowing categories:
METHODS FOR THE EUTHANASIA
OF DOGS AND CATS
RECOMMENDED
This method is considered best practice because it
consistently produces a humane death when used asthe sole means o euthanasia.
ACCEPTABLE
These methods also produce a humane death whenused as the sole means o euthanasia. However, there
are practical limitations to their use.
CONDITIONALLYACCEPTABLE
These methods are acceptable only with caveats, dueto the nature o the technique, potential or operatorerror, or saety hazards to personnel. These methods
may not consistently cause death humanely.
NOTACCEPTABLE
These methods are inhumane and are not consideredacceptable or the euthanasia o dogs and cats.
Some methods o euthanasia can be used incombination with pre-euthanasia drugs, and these arediscussed ater the summary table. A detailed overview
o each euthanasia method, giving rationale or theircategorisation, is provided on pages 1521.
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METHO
DSFOR
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CATS
RECOMMENDED
Method Remarks
Intravenous (IV) injection o 20%
Pentobarbitone solution
Barbiturate
Page 15
Regarded as best practice
Rapid acting
Rapid loss o consciousness, ollowed by cardiac arrest
May be used in combination with a pre-euthanasia drug i required or
earul, ractious or aggressive animals
No distressing side eects
Requires training
Relatively cheap
Not licensed or use in all countries
Cost and availability may vary rom country to country
Combinations o high concentrations o barbiturate with a local
anaesthetic may also be available and suitable i given intravenously as a
euthanasia agent
ACCEPTABLE
Method Remarks
Intraperitoneal (IP) injection o
20% Pentobarbitone solution
Barbiturate
Page 15
Slow acting
Takes longer to take eect than IV injection: 1530 minutes (dependent
upon the species and size o the animal)
A larger dose may be required than i given intravenously
May be used when collapsed or poor venous access precludes IV injection
May not be suitable or the euthanasia o larger animals
The use o pre-euthanasia drugs may prolong the time until death
May cause irritation to the peritoneum, particularly with
concentrations >20%
Can be combined with a local anaesthetic to reduce the risk o irritation
Animal may become distressed when it starts to lose consciousness
May be a practical alternative when IV injection is dicult e.g. or
ractious stray or eral cats, neonatal kittens and puppies. It is advisable to
return cats to a secure cage ater injection as they may become distressed
while the drug takes eect
Intravenous (IV) injection o
anaesthetic agents, given as an
overdose
e.g. Thiopentone or Propool;
Thiobarbiturate or Phenol
compound
Page 16
Rapid acting
Rapid loss o consciousness
May be suitable i animals are already anaesthetised or surgery and,
on humane grounds, not permitted to regain consciousness
Relatively large volumes or high concentrations required to euthanase
animals, potentially making it impractical or routine use depending upon
the commercial availability o the preparation
Under-dosing may lead to recovery
May be used in combination with a pre-euthanasia drug i required
Requires training
Cost may preclude routine use
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CONDITIONALLYACCEPTABLE
Method Remarks
Intracardiac (IC) injection o 20%
Pentobarbitone solution
Barbiturate
Only acceptable i animals are
anaesthetised by other means prior
to its administration (page 14)
Page 15
Rapid acting
Only suitable in collapsed, unconscious animals, or very young puppies
and kittens
May be suitable i animals are already anaesthetised or surgery and, on
humane grounds, not permitted to regain consciousness
Intracardiac route may be painul in ully conscious animals
Requires training, skill and knowledge o anatomy to ensure penetration o
the heart is successul on the rst attempt
Same licensing restrictions apply as with IV injection
Oral (PO) administration o
Pentobarbitone
Barbiturate
Only acceptable or neonatal
animals or to sedate animals prior
to intravenous injection o 20%
pentobarbitone solution
Page 15
Slow acting
Takes longer to take eect than IV injection (over 30 minutes)
May be suitable or neonates (within the rst ew hours/days o lie) aspoor venous access precludes IV injection
Not suitable or the euthanasia o larger/older animals
May be used to sedate animals prior to euthanasia with intravenous
injection o Pentobarbitone
Liquid orm o the drug may be detected by animals in their ood and
ingestion is avoided
Powdered orm may be delivered in gelatine tablets and hidden in ood to
encourage consumption
Animal may become distressed when it starts to become unconscious
Same licensing restrictions apply as with IV injection
Intravenous (IV) injection o T61
in a controlled manner, ater prior
sedation
Contains 3 drugs: general
anaesthetic, local anaesthetic and
curariorm-like agent
Only acceptable i animals are
sedated by other means prior to its
administration and injection rate is
slow (page 13)
Page 16
Rapid acting
Causes death by respiratory collapse due to paralysis o the diaphragm
and intercostal muscles, resulting in asphyxiaRequires slow, steady rate o injection
Precise rate o injection is required: its use in ractious animals is
problematic
Intense pain may result i the injection is given too quickly, due to muscle
paralysis prior to loss o consciousness
It should never be used without prior sedation to permit slow rate o
injection
Requires training and skill
No longer available or use in the United States
Intravenous (IV) or intracardiac
(IC) injection o potassium chloride
(KCl) ater general anaesthesia
Concentrated electrolyte solution
Only acceptable i animals are
anaesthetised by other means prior
to its administration (page 14)
Page 16
Rapid acting
Causes death by cardiac arrest
It should never be used without prior general anaesthesia to achievesucient insensibility and analgesia, to block the painul side eects o
this method
Requires training to ensure operator can assess suitability o anaesthetic
depth prior to use o KCl
Prior use o narcotic and analgesic mixtures adds signicantly to the cost
and prolongs the time o the procedure
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CONDITIONALLYACCEPTABLE
Method Remarks
Intravenous (IV) or intracardiac
(IC) injection o magnesium
sulphate (MgSO4) ater general
anaesthesia
Concentrated electrolyte solution
Only acceptable i animals are
anaesthetised by other means prior
to its administration (page 14)
Page 17
Rapid acting
Causes death by cardiac arrest
It should never be used without prior general anaesthesia to achieve
sucient insensibility and analgesia, to block the painul side eects
Requires training to ensure operator can assess suitability o anaesthetic
depth prior to its use
Large volumes are required or euthanasia
A saturated solution is required but this makes the liquid very viscous and
can result in diculty o administration
Prior use o narcotic and analgesic mixtures adds signicantly to the cost
and prolongs the time o the procedure
Inhalation o gaseous anaestheticssuch as halothane, enurane,
isourane and sevourane
Volatile inhalation anaesthetics
Page 17
Slow actingRequires high concentrations to be eective
Only suitable or small animals (weighing
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NOTACCEPTABLE
Method Remarks
Intravenous (IV) injection o T61
when used alone
Contains 3 drugs: general
anaesthetic, local anaesthetic and
curariorm-like agent
Page 16
May produce intense pain and causes death by paralysis o muscles
leading to asphyxiation prior to loss o consciousness i the injection rate
is too quick
Not acceptable when used alone or euthanasia
No longer available or use in United States
Intravenous (IV) injection o
potassium chloride (KCl) given
alone or only with prior sedation
Concentrated electrolyte solution
Page 16
Cardiotoxic causes cardiac arrest without rendering the animal
unconscious
Produces severe cardiac pain as a result
Sedation provides insucient analgesia to block painul side eects o
euthanasia agentNot acceptable when used alone or euthanasia
Intravenous (IV) injection o
magnesium sulphate (MgSO4)
given alone or only with prior
sedation
Concentrated electrolyte solution
Page 17
Causes cardiac arrest without rendering the animal unconscious
May cause intense pain and distress
Sedation provides insucient analgesia to block painul side eects o
euthanasia agent
Not acceptable when used alone or euthanasia
Oral (PO) or intravenous (IV)
administration o chloral hydrate
(CH)
Chemical reagent with sedative/
hypnotic properties
Page 17
Slow acting
Death results rom depression o the central nervous system resulting in
hypoxiaResults in convulsions, muscular contractions and gasping
Distressing and painul side eects
Large volumes are required to be eective
Not acceptable or euthanasia
Inhalation o nitrogen (N) or
nitrogen/argonmixtures
Gases
Page 18
Slow acting
Death due to hypoxia rom paralysis o the respiratory centre
Hypoxia may occur beore loss o consciousness even at high
concentrations, which is distressing or animals
Vocalisation, convulsions and tremors have been observed prior to death
Very young animals (
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NOTACCEPTABLE
Method Remarks
Inhalation o carbon monoxide
(CO)
Gas
Page 19
Slow acting
Highly variable time taken to lose consciousness and can take up to two
minutes at 6% concentration
Death by hypoxia
Vocalisations and agitation observed in dogs and this may occur while
they are still conscious
Distressing side eects observed in cats during induction
Animals
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NOTACCEPTABLE
Method Remarks
Electrocution
Physical method
Page 20
Although it is theoretically possible to apply a suitable current and voltage
across the skull (so that it passes through the animals brain) by trained
personnel using suitable electrodes, it is WSPAs experience that such
conditions are never achieved in practice
Whole body exposure to the electric current in an electrocution chamber is
not acceptable
Painul and inhumane under practical conditions
Dangerous to personnel
Not acceptable or euthanasia
Decompression
Physical method
Page 20
Slow acting
Death results rom hypoxia
Pain and distress results rom expanding trapped gases in the body prior
to the animal becoming unconsciousImmature animals are tolerant o hypoxia and require longer periods o
decompression beore respiration ceases
Aesthetically abhorrent as unconscious animals may bloat, bleed, vomit,
convulse, urinate and deecate during decompression
Totally unacceptable
Hanging
Physical method
Page 21
Death by asphyxiation rom strangulation
Causes ear and distress
Totally unacceptable
Drowning
Physical method
Page 21
Slow acting
Prolonged death by asphyxiation caused by immersion in water
Causes ear and severe stressTotally unacceptable
Strychnine
Poison: Neuromuscular blocker
Page 21
Slow acting
Prolonged time or the animal to die and this can be highly variable rom
minutes to days depending upon the dose ingested
Causes violent and painul muscle contractions resulting in asphyxiation
Extreme danger to personnel
Totally unacceptable
Cyanide
Poison
Page 21
Slow acting
Causes death by hypoxia and cardiac arrest
Results in violent convulsions and causes pain and distress while the
animal remains conscious
Extreme danger to personnel
Totally unacceptable
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PRE-EU
THANASIADRUGS
Pre-euthanasia drugs (tranquillisers, sedatives,
immobilisers or general anaesthetics) may be requiredto acilitate sae and humane handling o animalsprior to euthanasia, particularly i they are ractious,
aggressive or earul. Moreover, the prior administrationo suitable pre-euthanasia drugs may be necessary withsome conditionally acceptable euthanasia agents to
ensure they are humane.
The majority o these drugs require minimal animalhandling during their administration as they arepreerably given as a subcutaneous injection (unlesscontraindicated by the manuacturer), or sometimes as
an intramuscular injection or even via oral dosing. Theoperator then withdraws and waits or the drug to takeeect beore administering the euthanasia agent. Somepre-euthanasia agents, however, will require intravenous
administration. An important point is that the use othese drugs can add signicantly to the time taken toperorm euthanasia and this should be considered in
advance to saeguard animal welare.
There are several drugs that are commonly used prior to
euthanasia. It is essential that operators understand thedierent eects each o these has on an animal, as theiruse may not be appropriate or humane as an adjunct to
potentially distressing or painul euthanasia methods.Terms such as tranquillisation, sedation, immobilisationand anaesthesia describe the actions o these drugs.
These terms are sometimes incorrectly used as ithey were interchangeable, their specic meaning anddierent eects are explained below.
Tranquillisers
These drugs have some eects in decreasing ear andapprehension while the animal remains awake, making
it calm when exposed to low level stimuli. However,they have no analgesic eects and the animal is readilyaroused by painul stimulation. Oten they give a alsesense o security to someone handling an animal, which
appears calm but may then display enhanced and evenviolent responses to a strong stimulus such as a loudnoise or an approach by a person. This is potentially
dangerous to anyone who has to perorm euthanasia.
Example o common tranquillising agent:
Acepromazinemaleate(ACP) is a common tranquilliserused in animals, and has some depressing eects
on the central nervous system. Its principal use isin combination with other opiate drugs as a pre-
medication given beore anaesthesia. It will noteliminate any pain associated with euthanasia agents,and increasing the dosage above what is recommendedwill have little urther eect over the tranquillising
PRE-EUTHANASIA DRUGS
action, hence this drug cannot be recommended or sole
use prior to euthanasia with agents that may cause pain.Moreover ACP should not be used alone to calm earulanimals prior to euthanasia with any, even non-painul
agent, as it does not alter the animals perception o thesituation, merely its ability to respond.
Sedatives
These drugs depress the activity o the central nervous
system, resulting in drowsiness and muscle relaxation sothat animals become uncoordinated. I they are given insuciently high doses an animal may all into a sleep-likestate. However, they may not render the animal insensible
to pain: the animal generally remains conscious butcalm. As with tranquillisers, sedated animals can becomearoused by strong stimulation such as a painul procedure,
making their behaviour unpredictable.
Examples o common sedative agents:
Xylazine(Chanazine,Rompun,Virbaxyl,Xylacare)is a common sedative used with both large animals(equines and livestock) and small (companion) animals.
It induces muscle relaxation and also possesses someanalgesic properties. I used alone this drug may not bea suitable pre-euthanasia agent or some conditionally
acceptable euthanasia methods, as it does not inducesucient anaesthesia. In addition this drug will cause adrop in blood pressure, rendering subsequent intravenous
injection o euthanasia agents more dicult.
Medetomidine (Domitor) can induce sedation but must
be given in a suciently large dose. Its use also resultsin muscle relaxation and provides some analgesia. Aswith Xylazine, i used alone this drug may not be a
suitable pre-euthanasia agent or some conditionallyacceptable euthanasia methods, as it does not induce
sucient anaesthesia. Also as with Xylazine, thisdrug will cause a drop in blood pressure, renderingsubsequent intravenous injection o euthanasia agentsmore dicult.
Butorphanol (Torbugesic, Torbutrol) has some analgesicproperties. But both its sedative and analgesic eects
are dose dependent. However, this drug may not besuitable or sole use with some conditionally acceptableeuthanasia methods, as it does not induce sucientanaesthesia or analgesia. Its use is unlikely to produce
the drop in blood pressure caused by Xylazine orMedetomidine.
ImmobilisersThese drugs render the animal immobile by inducingparalysis. The animals body may become rigid and stiand the animal appears unresponsive to external stimuli
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PRE-EU
THANASIADRUGS
such as sound. However, the animal can still eel painand thereore the sole use o immobilisers with painul,
conditionally acceptable euthanasia agents is notacceptable.
Example o common immobilising agent:
Ketamine (Ketaset, Vetalar) classed as a dissociativeanaesthetic, can also be used or restraint. It may
induce muscle rigidity when used alone and producesan altered state o consciousness (catatonia: not a losso consciousness). Unless combined with other drugs
such as Medetomidine, Xylazine and/or Butorphanol toproduce sucient analgesia and anaesthesia, it is notacceptable as a sole pre-euthanasia drug or use with
euthanasia agents that may cause pain. Injection byintramuscular or subcutaneous routes may be painul
and its rate o absorption can be altered.
Anaesthetics
These result in loss o consciousness and provide
good analgesia and muscle relaxation, so that surgicalprocedures can be undertaken.
Examples o common anaesthetic agents:
Tiletamine-Zolazepam(Telazol,Zoletil).This drugcombination oers good anaesthesia and allows or an
intracardiac injection o pentobarbitone or intravenousor intracardiac injection o conditionally acceptablemethods o euthanasia when properly administered.
This drug combination should be injectedintramuscularly.
Thiopentone and Propool. These drugs will result insucient anaesthesia to allow or intracardiac injectiono pentobarbitone or intravenous or intracardiac
injection o conditionally acceptable methods oeuthanasia. However, both o these drugs must be givenintravenously and may be unsuitable or use in animals
that are dicult to handle or restrain.
Combinations o pre-euthanasia drugs
Combinations o drugs may enhance their suitabilityas a prelude to euthanasia, especially i they possess
dierent, complementary analgesic and anaestheticproperties (e.g. Ketamine and Butorphanol). Suchcombinations should be chosen to render the animalinsensible to the pain that may result rom some
conditionally acceptable euthanasia methods. Whenusing a combination o drugs it is vital that a sucientdose o each drug is used, and that ample time is
allowed or them to reach their maximum eect beoreeuthanasia is undertaken. Moreover, animals should bemaintained in a quiet and calm environment as external
stimulation can prolong the time taken or drugs totake eect. Both o these actors can be aectedby an animals species (dog or cat), age, body size,
demeanour and metabolism, so the individual animals
drug requirements must be careully determined beorethis course o action.
Oral administration o drugs or combinations o drugsas a prelude to euthanasia has been explored or dogs(Ramsay and Wetzel, 1998) and cats (Wetzel and
Ramsay, 1998; Grove and Ramsay, 2000). For dogsa combination o Tiletamine-Zolazepam/Acepromazineor Pentobarbitone used alone consistently induced
sedation and lateral recumbency (Ramsay andWetzel, 1998). However, the time taken to produceproound sedation was prolonged (3090 minutes)
and highly variable between individuals.
In addition, the sole use o Pentobarbitone was
associated with struggling to stand and prolongedataxia during the onset o ull sedation. Theseundesirable eects were not observed or the
Tiletamine-Zolazepam/Acepromazine combination
and they may be ameliorated i Acepromazine isadded to the Pentobarbitone dose (Ramsay andWetzel, 1998), but this combination was not tested.
It is important to note that liquid preparations o thedrugs mixed with ood were detected and rejectedby dogs (Ramsay and Wetzel, 1998). Uptake by
dogs was greatly improved when the required doseo powdered preparations was placed in gelatinecapsules and hidden in canned (wet) ood.
The oral administration o Detomidine/Ketaminecombination was successul in sedating cats (Wetzel
and Ramsay, 1998; Grove and Ramsay, 2000)in comparison with other drugs tested (Ketamine,Detomidine, and Xylazine/Ketamine, Medetomidine/
Ketamine combinations). This particular combinationproduced reliable sedation within 1025 minuteso oral dosing (Grove and Ramsay, 2000). However
there are several undesirable side eects that maypreclude this rom routine use. The oral treatmento cats with all combinations tested (Detomidine/
Ketamine, Xylazine/Ketamine and Medetomidine/Ketamine) resulted in vomiting and excessivesalivation in some cats (Wetzel and Ramsay, 1998;
Grove and Ramsay, 2000) and is likely to causedistress to cats during induction prior to loss oconsciousness.
Food dosed with these types o drug is unpalatable,hence precluding accurate administration via ood.
However, the method o dosing used in these tests(squirting the liquid medicants directly into the catsmouth) is dicult to perorm remotely with any
accuracy. The handling o ractious or aggressive catsor oral dosing is likely to cause stress to the animals,thus presenting a welare issue as well as a potential
hazard or operators. Furthermore, Detomidine maynot be licensed or use in cats and guidelines or o-label use should be ollowed.
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The ollowing discussion provides greater detail
regarding the use and suitability o each methoddescribed in the summary table, to explain the reasonsor their categorisation. They are arranged by mode o
action and their acceptability or euthanasia.
Euthanasia agents are generally classied by their physical
characteristics: non-inhalant (injectable) pharmaceuticalagents; inhalant agents (gas mixtures); physical
methods; and poisons. They work by one o three modeso action (Close et al., 1996; Beaver et al., 2001):
Hypoxiadeathresultsfromreducingtheamountof
oxygen available to the animals cells and tissues.
Directdepressionofthenervecellsintherespiratory
centres o the brain necessary or maintaining lie
unction, leading to a loss o consciousness ollowedby death.
Physicaldisruptionofbrainactivitythrough
concussion, direct destruction o the brain, orelectrical depolarisation o nerve cells, leading to
rapid unconsciousness. Death occurs owing todestruction o the areas o the brain that controlcardiac and respiratory unctions.
Non-inhalant, injectable
pharmaceutical agentsBarbiturate, injectable anaesthetic agents,
T61, potassium chloride, magnesium sulphate
and chloral hydrate
RECOMMENDED
BarbituratesBarbiturates act by depressing the central nervoussystem, starting with the cerebral cortex, which
causes rapid loss o consciousness progressing toanaesthesia (Beaver et al., 2001). Their ecacy asanaesthetic agents ree rom distressing side eects iswidely recognised. With sucient dosages (overdose)
barbiturates induce respiratory and cardiac arrestby depressing the centres within the central nervoussystem that control these lie-maintaining unctions.
For euthanasia o dogs and cats, barbiturates thathave been specically ormulated as euthanasia
agents are preerred. The intravenous injection o 20%
Pentobarbitone solution is regarded as the most humanemethod o euthanasia or dogs and cats (Reilly, 1993;
Close et al., 1997; Beaver et al., 2001; European FoodSaety Authority, 2005) (see Annex 2). Dogs and catsare simply put to sleep; there is no audible or other
expression o pain. In some individuals a terminalgasp may occur when the animal is unconscious and
although this may distress some observers, it is not anexpression o pain or discomort, merely a refex action.Pentobarbitone is easy to use, relatively cheap and sae
or the operator (provided that it is not misused, e.g.deliberately sel-injected).
When the restraint necessary or giving an intravenous
injection would distress an animal or pose undue riskto the operator then prior sedation or anaesthesia
(pages 1314) or other accepted alternative routes oadministration should be employed (Beaver et al., 2001).
In an emergency situation the drug can be injecteddirectly into the peritoneal cavity (intraperitoneal).The time taken or the animal to lose consciousness
and die (1530 minutes) is longer than i the drug isgiven intravenously (a ew seconds). A higher doseo Pentobarbitone is required or intraperitoneal
euthanasia (Grier and Schaer, 1990; Sinclair, 2004)and it can cause irritation to the peritoneum, but thiscan be avoided i the drug is combined with a localanaesthetic.
There are no published reports on the use ointraperitoneal injection in dogs; nevertheless Sinclair
(2004) provides anecdotal accounts that dogsstruggle more than cats; repeatedly attempting toright themselves during the induction phase. For this
reason intraperitoneal injection may be unsuitable orlarger animals.
While most cats, kittens and puppies appear to advancemore smoothly to unconsciousness than adult dogs, theyshould be closely monitored, and conned to a warm,
dark, quiet place to acilitate distress-ree induction.The combination o Pentobarbitone and Phenytoin (acardiotoxic anticonvulsant drug) may be unsuitable
or intraperitoneal injection, because o concerns overthe dierential absorption rates o the two compounds(Sinclair, 2004). The eects o Phenytoin on the heart
may occur beore the Pentobarbitone component hascaused unconsciousness (Fakkema, 1999 cited bySinclair, 2004).
The technique or intrahepatic injection oPentobarbitone has been reported by Grier and
Schaer (1990). When correctly administered,its action is considerably aster in comparison to
injection via the intraperitoneal route, with cardiacstandstill being reported within 1114 minutes.However, perorming accurate intrahepatic injection istechnically dicult and may cause animals discomort
(Sinclair, 2004). Administration outside o the target
DISCUSSION OF
EUTHANASIA METHODS
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organ (the liver) is associated with excitement, whichmay also be distressing to the operator (Grier and
Schaer, 1990).
Injection o 20% Pentobarbitone directly into the heart
(intracardiac) may be suitable in collapsed, unconsciousanimals. However, this requires skill and knowledge oanatomy because ailure to inject into the correct place
will cause pain. It should only be used by experiencedtechnicians in an emergency.
It may be appropriate to administer liquid orm o a
suitable concentration o Pentobarbitone orally (bymouth) to neonatal puppies and kittens (within the rstew hours/days o lie) or euthanasia, as intravenous
access is dicult. The time taken or eect is longer
than i administered intravenously.
It should be noted that the time taken or oraladministration o Pentobarbitone to reach its maximumeect is prolonged (3090 minutes) and highly variable
between individuals given the same dose (Ramsay andWetzel, 1998). In addition to the lengthy inductiontime, other undesirable side eects may make this
method unsuitable or routine use, or instance somedogs may struggle prior to becoming ully sedated(Ramsay and Wetzel, 1998).
Oral administration o Pentobarbitone or euthanasiao juvenile or adult dogs and cats is unsuitable.
It may, however, be used to produce sedation orlight anaesthesia to precede intravenous injectiono Pentobarbitone or the euthanasia o ractious or
aggressive animals (Ramsay and Wetzel, 1998;Sinclair, 2004).
Some euthanasia products have been ormulated to usebarbiturates combined with a local anaesthetic agentor Phenytoin. The pharmacological dierences are
inconsequential when injected intravenously but suchcompounds may be more easily obtained insome countries.
WSPA considers the use o intravenous Pentobarbitoneor euthanasia o dogs and cats as best practice
(Annex 1, Annex 2) and its use is stronglyrecommended provided that it is legally permissibleand operators have been given appropriate training.However, suitable barbiturates are not always
available and in these circumstances WSPA urgesveterinary authorities, animal welare organisations andgovernments to strive to make these drugs legally and
easily available to the relevant proessionals.
ACCEPTABLE
Other intravenous anaesthetics
Other barbiturate drugs commonly used asanaesthetics, such as Thiopentone and newer agentssuch as Propool,will produce painless euthanasia igiven intravenously as overdoses (Annex 1). They work
in a similar manner to that described above, rapidly
inducing unconsciousness and death. However,larger volumes are required or euthanasia (Annex 1)and oten this makes their use more cost prohibitive
or routine euthanasia than Pentobarbitone. Inaddition these agents should not be given other thanintravenously, as they may cause tissue reactions at
the site o injection leading to pain and discomort. Aswith Pentobarbitone, they may be subject to restrictedlicensing practices.
ACCEPTABLEWITHCONDITIONS
T61
T61 is a mixture o three compounds (embutramide,
mebezonium iodine, tetracaine hydrochloride),which provide a combination o muscle paralysis
(via curarirom-like mechanisms), local anaestheticand general anaesthetic actions (Giorgi and Bertini,2000). The muscle paralysing agent rapidlyinduces respiratory collapse by paralysing the
animals diaphragm and intercostal muscles. Alocal anaesthetic acts to reduce (painul) tissueinfammation at the site o the injection, and the
general anaesthetic induces loss o consciousness.
The three compounds have dierent speeds o
absorption in the body (Beaver et al., 2001) andthere is a risk that i the injection is given too quicklythe animal will remain conscious during respiratory
collapse, which may produce pain (Giorgi and Bertini,2000) and distress (Hellebrekers et al., 1990) priorto death. For this reason T61 should be given by aslow and precise rate o intravenous injection (Beaveret al., 2001). This is likely to be dicult with animalsthat are anxious when being handled or restrained.
T61 should thereore only be used with prior sedation(page 13) to allow or close monitoring o injectionrate and to avoid causing pain to the animal. It should
never be given other than intravenously (Annex 1), asthe onset o action o each o the three constituentscan be altered when administered via alternative
routes (Beaver et al., 2001). T61 is no longer
available or use in the United States.
ACCEPTABLEWITHCONDITIONS
Potassium chloride (KCI)
The potassium ion is cardiotoxic (has a toxic eect
on the heart muscle) and rapid injection o potassiumchloride (KCI) as a saturated salt solution causescardiac arrest leading to death i given intravenouslyor by the intracardiac route o injection. It has no
anaesthetic or analgesic properties so i used aloneit causes animals intense pain prior to death. HenceKCI is only acceptable as the nal stage o euthanasia
in animals given prior narcotic or analgesic agents to
block its painul side eects (page 14). It is essentialthat personnel perorming this technique are trained
and knowledgeable in anaesthetic techniques. Theyshould be competent at assessing anaesthetic depthappropriate or subsequent administration o KCI.
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Euthanasia with KCl is only considered to be acceptablei animals are under general anaesthesia, characterised
by loss o consciousness, loss o response to unpleasant(including painul) stimuli and an absence o refexmuscle responses (Beaver et al., 2001). KCI can be
easily acquired, transported and mixed with water toorm an injectable, supersaturated solution (Annex1) to kill animals. However, the use o suitable pre-
euthanasia drugs will signicantly increase both thetime taken to perorm euthanasia and its cost.
ACCEPTABLEWITHCONDITIONS
Magnesium sulphate (MgSO4)
Magnesium sulphate (MgSO4) is a neuromuscularblocking agent. I delivered intravenously as a saturated
salt solution it will lead to cardiac and respiratory arrestollowed by death (Close et al., 1996). However, itcauses muscle paralysis (inducing respiratory arrest)without prior loss o consciousness (Beaver et al.,
2001); the animal thereore remains conscious butimmobile until the brain succumbs to lack o oxygen(European Food Saety Authority, 2005). Moreover
MgSO4 has no analgesic or anaesthetic propertiesto block the painul side eects and its sole use asan agent or euthanasia is inhumane (Close et al.,
1996, 1997; Beaver et al., 2001; European FoodSaety Authority, 2005). Dogs have been observed toexperience violent muscle spasms and contractions,
vocalising, gasping or breath and convulsion seizuresprior to death (Avariez and Caday, 1958), indicatingthat they experience pain and distress. As with
using KCI or euthanasia, MgSO4 is only acceptableas the nal stage o euthanasia in animals that areanaesthetised (page 14) and hence unconscious and
unresponsive to noxious (including painul) stimuli (andtheir refex muscle responses can no longer be evoked).Again, this requirement or pre-euthanasia drugs
signicantly adds to both the time taken to perormeuthanasia and to its cost. Furthermore, large volumeso MgSO4 are required (Annex 1) and an eective
saturated solution becomes very viscous and dicult tohandle or injection.
NOTACCEPTABLE
Chloral hydrate (CH)
Chloral hydrate (CH) acts slowly to depress the braincentres responsible or controlling respiration and
during the time taken to become unconscious animalsdisplay muscle spasms, gasp or breath and vocalise;indicating that they are in distress (Carding, 1977;Close et al., 1996). This drug has no anaesthetic or
analgesic properties to block the painul and distressingside eects and it is unacceptable or use in dogs andcats. Even with prior use o anaesthetics its slow mode
o action and the large volume required or it to be
eective make it unacceptable or euthanasia (Carding,1977; Beaver et al., 2001).
Inhalant agents (gas mixtures)
Anaestheticgases,nitrogen/argon,carbondioxide,
carbon monoxide, nitrous oxide and ether
General considerations
Inhalation agents used or euthanasia include volatileliquid anaesthetics and gases or gas mixtures that resultin hypoxia; delivered at increasing concentrations they
displace oxygen in the air breathed by animals (inspiredair) thereby lowering the concentration o oxygenreaching the lungs and tissues (Close et al., 1996).
To be eective, inhaled agents must reach a certain(minimum) concentration in the animals lungs (Beaver et
al., 2001). This means they do not induce an immediateloss o consciousness, and death ollows at some
considerable time later (European Food Saety Authority,2005). The humane induction o unconsciousness is
important, and any inhalation agents used must notbe unpleasant or the animal to breathe or producepain or distress prior to loss o consciousness (Closeet al., 1996, 1997; Leach et al., 2004; European FoodSaety Authority, 2005). In particular, inhalation agentsthat produce convulsions prior to unconsciousness are
unacceptable or euthanasia and should not be used(Close et al., 1996; Beaver et al., 2001).
Very young animals are particularly resistant to theeects o lowered oxygen concentrations (hypoxia/anoxia) because their haemoglobin (the oxygen-
transporting molecule in red blood cells) has a higheranity or oxygen than that o adults (Pritchett et al.,2005 cited by European Food Saety Authority, 2005);
an adaptation to being in the uterus. Young animals,thereore, take longer to die rom hypoxia than adults(Close et al., 1996; Beaver et al., 2001).
Inhaled agents may take longer to build up in the lungsand be eective in animals that are ill, injured or old, as
these animals may show decreased ventilation (shallowbreathing), making agitation more likely beore loss oconsciousness (Beaver et al., 2001).
In addition to these general considerations or animalwelare, the health and saety o operators is a major
concern with some o these methods. Both acute andchronic exposure to these agents can have toxic eectson humans (National Institute or Occupational Saety
and Health, 1977).
ACCEPTABLEWITHCONDITIONS
Anaesthetic gases
Halothane, Enfurane, Isofurane and Sevofurane arecommonly used as anaesthetic agents and can be
used or euthanasia i they are given as an overdose(Annex 1) (European Food Saety Authority, 2005).
However, these agents dier in the speed at whichthey induce unconsciousness and they possessvarying degrees o pungency, which animals may ndunpleasant (Leach et al., 2004; European Food Saety
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Authority, 2005). In addition, animals may struggle andbecome anxious during induction (Beaver et al., 2001)
because anaesthetic vapours may be irritating (Leach et
al., 2004). They are thereore not generally consideredto be suitable as sole agents or euthanasia in larger
animals (>7kg). Halothane is preerred because it maybe less aversive during induction (Leach et al., 2004)and produces anaesthesia more rapidly than the other
agents (Beaver et al., 2001; European Food SaetyAuthority, 2005).
Inhalation anaesthetic agents are vaporised and
delivered into chambers, via a ace mask or tube romanaesthetic machines; they are combined with air/oxygen during induction to prevent hypoxia (Closeet al., 1996, Beaver et al., 2001). The liquid states
o these agents are highly irritant, and animalsshould only be exposed to vapours. Chambers and
anaesthetic machines should be properly designed toensure that the gas is evenly distributed and that theanimal is rapidly exposed to eective concentrations
o the agent (Close et al.,1996). It is important touse equipment that is well maintained and to havescavenging units (devices used to reduce the pollution
in the air) to prevent personnel being exposed to theanaesthetic agents, as exposure to trace concentrationso anaesthetic gases is recognised as a human health
hazard (National Institute or Occupational Saety andHealth, 1977).
The large doses required or euthanasia are expensiveand tend to make this method cost prohibitive. Withthe diculty in administration and human health
aspects, this means that although this can be anacceptable method o euthanasia or small dogs andcats there are more suitable methods available (Closeet al., 1997; Beaver et al., 2001). The greatest valueo anaesthetic gases may be or the euthanasia o smallanimals (
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beore unconsciousness (Danneman et al., 1997; Leachet al., 2004). The cumulative stress associated with the
induction o unconsciousness when using CO2 is a seriouswelare concern (European Food Saety Authority, 2005).WSPA thereore considers this to be an unacceptable
method or the euthanasia o dogs and cats.
NOTACCEPTABLE
Carbon monoxide (CO)
Methods o generating carbon monoxide (CO) gas
or euthanasia o animals have included chemicalinteraction arising rom combining sulphuric acidand sodium ormate and the use o exhaust umes
produced rom idling petrol engines (Carding, 1977).Both o these techniques produce irritants that are
likely to result in considerable distress to animals andare thereore detrimental to the welare o dogs andcats (Carding, 1968, 1977; Close et al., 1996; Beaveret al., 2001), and hence their use is not acceptable.
Commercially compressed CO delivered rom cylindersinto specially constructed chambers has been used orthe mass euthanasia o dogs and cats.
CO combines with haemoglobin in the red bloodcells, decreasing the oxygen carrying capacity o theanimals blood. As a result, less oxygen is delivered
to the tissues and cells (hypoxia), which leads tounconsciousness, ollowed by death (Chaliouxand Dallaire, 1983). Although the animal becomes
unconscious within 12 minutes (variable betweenindividuals), death as conrmed by cessation oheartbeat does not occur until 1020 minutes ater
initial exposure to CO at concentrations reaching6% (Moreland, 1974; Chalioux and Dallaire, 1983;Dallaire and Chalioux, 1985). Although the welare
aspects o this method have not been well researched,a ew studies have reported that prior to loss oconsciousness dogs show signs o anxiety, including
moaning vocalisations (Carding, 1968; Chalioux andDallaire, 1983; Dallaire and Chalioux, 1985) andsigns o agitation (Moreland, 1974; Chalioux and
Dallaire, 1983). Furthermore, there is some concern
that the onset o convulsions (Close et al., 1996) andmuscular spasms (Moreland, 1974) may precede loss
o consciousness (Chalioux and Dallaire, 1983; Close
et al., 1997). Equally distressing behaviours have beenobserved in cats during the initial phase o euthanasia
using this method (Simonsen et al., 1981).
Use o the tranquiliser ACP prior to euthanasia with
CO signicantly reduced some o the behavioural andphysiological responses o dogs, but sucient timemust be allowed or ACP to reach its maximum eect
beore exposure to CO (Dallaire and Chalioux, 1985).
In addition to the risks or animal welare, CO is
extremely hazardous or humans because it is highlytoxic and dicult to detect. Even chronic low levelexposure is considered a human health hazard and isassociated with cardiovascular disease (Beaver et al.,
2001).
There are several practical limitations associated withthis method o euthanasia. Firstly, the construction,
diligent maintenance and careul operation o specialchambers are essential to reduce the risk to humanand animal welare; and these are likely to be costly.
Secondly, use o CO to euthanase certain groups oanimals is considered unacceptable (Humane Societyo the United States, undated). In particular, animals
under our months old (resistant to hypoxia); thosewith impaired breathing and or low blood pressure(due to systemic disease, injury or old age) will take
longer to succumb, causing additional distress priorto death. Use o CO inhalation to euthanase obviouslypregnant animals is also discouraged as the unborn
young will not be exposed to the gas and will die slowlyas a result o suocation, due to death o the mother
(Humane Society o the United States, undated).Moreover, unconscious dogs urinate, deecate andregurgitate (Moreland, 1974) making this aestheticallyobjectionable or operators and requiring chambers to
be thoroughly cleaned, adding to the time o use.
Although considered a conditionally acceptable method
o euthanasia by the American Veterinary MedicineAssociation (Beaver et al., 2001) and the HumaneSociety o the United States or some dogs and cats,
the many limitations o CO may make this method lesspractical, considerably slower and more expensive thanlethal injection (Humane Society o the United States,undated). There is also concern over the distressing
side eects o exposure to CO (European Food SaetyAuthority, 2005) while the animal is conscious (Staord,2006) and over the signicant danger to operators. For
these reasons WSPA considers this to be an unacceptablemethod or the euthanasia o dogs and cats.
NOTACCEPTABLE
Nitrous oxide (N20)
This gas is no longer considered appropriate as a soleanaesthetic agent as it does not induce anaesthesia
in animals even at 100% concentrations (Beaver
et al., 2001). I N20 is used on its own it produces
hypoxemia (low oxygen in the blood) (European FoodSaety Authority, 2005) beore respiratory or cardiacarrest (Beaver et al., 2001) and as a result animalsmay become distressed prior to loss o consciousness
(Beaver et al., 2001). This method is consideredinhumane and not acceptable or euthanasia.
NOTACCEPTABLE
Ether
This is a highly infammable volatile liquid, which maybe explosive under some circumstances. It must be
vaporised by the passage o a gas, normally oxygen,to be used as an anaesthetic. Ether is a relatively
dangerous substance to use and causes distress byirritation to the nasal passages and eyes to both theanimal and the operator (Close et al., 1996). This agentis not suitable or euthanasia, because o extreme risk tooperators and the detrimental eects on animal welare.
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Physical methods
Shooting using a ree bullet, penetrating captive bolt,
electrocution, decompression, hanging and drowning
General considerations
For several reasons physical methods or the euthanasiao dogs and cats are generally not recommended(Close et al., 1997). Some methods are likely to cause
severe pain and suering to animals and are thereoreconsidered inhumane, and unsuitable or euthanasia. Inaddition the high risk o equipment ailure, malunction
and operator error when used in practice will causepain and distress to the animals. The only physicalmethod considered conditionally acceptable by WSPA
shooting with a ree bullet could be used as alast resort in an emergency situation when no other
methods are possible, but not as routine.
Many o these methods may be aestheticallyobjectionable or personnel, making them distressingto perorm and urther increasing the stress that
operators may experience. Furthermore, i operatorsare distressed and dissatised themselves, there is anincreased likelihood o them becoming careless when
handling animals.
ACCEPTABLEWITHCONDITIONS
Shooting using a ree bullet
An accurate shot to the animals head will resultin immediate destruction o the brain and loss oconsciousness, ollowed by death (Carding, 1977).
However, specialist training and considerable skillis required to ensure that the bullet will penetratethe brain. In addition there is extreme danger to the
operators and any bystanders, and a rearm shouldnever be used in enclosed spaces as there is a risko ricocheting bullets. Moreover, the use o a rearm
is likely to be subject to strict local and nationalregulations. WSPA would only conditionally acceptthis method or use in an emergency situation, when it
is necessary to alleviate the suering o an individualanimal but no acceptable euthanasia methods are
possible, because the animal cannot be handled orgiven pre-euthanasia drugs.
NOTACCEPTABLE
Captive bolt
Although widely used and accepted as a stunningprocedure or the slaughter o large livestock species,this method is generally considered inappropriate ordogs and cats (European Food Saety Authority, 2005).
The penetrative captive bolt pistol must be placed incontact with the animals skull and precise positioningis essential so that the bolt penetrates the correct area
o the brain rst time. Animals must be adequately
restrained so that the head remains steady (Carding,1977; Dennis et al., 1988; Beaver et al., 2001), which
makes this method particularly dicult with earul andaggressive dogs and cats (Carding, 1977). Furthermore,
the conormational dierences between the skulls oindividuals and breeds o dogs increase the risk o amis-stun. The principle skull types are dolichocephalic
(long, narrow head), brachycephalic (short, wide heads)and mesaticephalic (medium proportions).
Use o a captive bolt may be aesthetically unpleasantto the operator, especially as urther measures arenecessary (e.g. pithing or exsanguination) to ensure death
(Beaver et al., 2001). The bleeding that occurs aterpenetration o the skull and ater urther pithing createsa hazard or the operator, due to the risk o coming into
contact with blood and brain matter. This risk may be oparticular concern in rabies-endemic areas.
As there is a high risk o mis-stunning through inadequate
use o the penetrating captive bolt, and hence causingpain and distress, WSPA considers this an unacceptable
method or the euthanasia o dogs and cats.
NOTACCEPTABLE
Electrocution
In theory it is possible to achieve euthanasia byapplying an appropriate electric current and voltagein a two-step process: rst, spanning the animals
brain to render it unconscious producing an eectivestun; second, applying sucient current acrossthe heart to produce cardiac brillation and death
rom hypoxia (Beaver et al., 2001). However, it isWSPAs experience that such ideal conditions arenever achieved in practice. There are grave concerns
over the suitability o the design (Carding, 1977)and maintenance o equipment, which, coupled withlack o training and misuse (Phillips, undated), make
this method inhumane. I an animal is not eectivelystunned, which is oten the case with whole bodyexposure to electric current in electrocution chambers
(Carding, 1977), death results rom cardiac brillationin a conscious animal, and hence involves excruciatingpain and distress. In addition this method may be
extremely hazardous to personnel, and is aestheticallyobjectionable as it causes violent extension and
stiening o the animals limbs, head and neck(Beaver et al., 2001).
WSPA regards electrocution as an unacceptable methodo euthanasia or dogs and cats, as the minimum
conditions necessary or it to be humane are oten notachieved in practice.
NOTACCEPTABLE
Decompression
This method requires the use o decompression
chambers. In theory the low ambient air pressure inthe absence o extra oxygen results in cerebral hypoxia,
leading to loss o consciousness ollowed by death(Carding, 1977). However, expansion o trapped gasesin body cavities leads to adverse physical eects, painand discomort (Close et al., 1996), and is likely tocause anxiety and stress in animals (Close et al., 1997).
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In addition this method may be aesthetically unpleasantor the operator as unconscious animals may bloat,
bleed, vomit, convulse, urinate and deecate duringdecompression (Hatch, 1982).
This method is inhumane and thereore not acceptableor the euthanasia o dogs and cats.
NOTACCEPTABLE
Hanging
Death results by asphyxiation rom constriction o thetrachea ater strangulation, causing the animals earand distress. This method is inhumane and its use is
condemned by WSPA.
NOTACCEPTABLE
Drowning
Prolonged death by asphyxiation ater immersion in
water (drowning) causes animals ear and severe stress(Close et al., 1996). This method is inhumane and itsuse is condemned by WSPA.
Poisons
Strychnine and cyanide
General considerations
These agents cause excruciating pain and distress to
animals.
NOTACCEPTABLE
Strychnine
Strychnine acts on the nervous system resulting in
painul muscle contractions and violent convulsions.The animal remains conscious and experiences extremepain and distress beore it dies as a result o suocation
(Lumb, 1985; Close et al., 1996; Beaver et al., 2001).This is an unacceptable agent or euthanasia as itsmode o action is inhumane.
NOTACCEPTABLE
Cyanide
Cyanide blocks oxygen uptake, leading to respiratorycollapse. It is accompanied by violent and painul
convulsions prior to the onset o unconsciousness anddeath (Hatch, 1982). In addition, the use o cyaniderepresents an extreme danger to people as they are
equally susceptible to its toxicity. The use o cyanide isinhumane and should never be a method o euthanasia.
The World Society or
the Protection o Animalsfrmly believes that in allsituations when euthanasiais deemed necessary themethods adopted should betruly humane. They shouldachieve rapid, painlessdeath and minimise earand distress to animals. Ourgoal is or all countries to
adopt the humane methodsendorsed by WSPA, and or
this document to be usedto encourage authorities tomake the recommendeddrugs available.
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REFERENCES
REFERENCES
Hellebrekers, L.J., Baumans, V., Bertens, A.P., Hartman, W. 1990. On the use
o T61 or euthanasia o domestic and laborator y animals; an ethical evaluation.
Laboratory Animals 24(3): 200204.
Herin, R.A., Hall, P., Fitch, J.W. 1978. Nitrogen inhalation as a method
o euthanasia in dogs.American Journal o Veterinary Research 39 (6):
989991.
Hewett, T.A., Kovacs, M.S., Antwohl, J.E., Taylor-Bennett, B. 1993. A comparison
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ANNEX
1
ANNEX 1: Dosages and routes o administration o
agents or euthanasia o dogs and cats
The inormation is rom those organisations using drugs or euthanasia
in the eld. The eects o many o these agents are dose dependent. Itis thereore essential that an accurate estimate o the animals weight isobtained prior to euthanasia. In addition the eects o these drugs may
be highly variable and dependent upon the individual animals physicalcharacteristics and circumstances. All manuacturers instructionsshould be consulted and adhered to.
Eutha
nasiaa
gent
Route
ofad
ministr
ation
Dosag
eRe
marks
Us
eofp
re-eut
hanasi
a
drugsind
icated
?
Pentobarbitonesolution
Injectablesolutions suitableor euthanasia(20%: 200mg/
ml)
Intravenous (IV) 150mg/kg or both dogs and cats Best practice
Carcass disposal recommendincineration
Not unlessthe animal isractious
Intraperitoneal(IP)
Proposed dosage schedule is23 x recommended dose or IVadministration when preparationscontaining concentrations o 390mg/ml o Pentobarbitone are used(Sinclair, 2004: p 397.)
120200 mg/kg as necessary(Bishop, 2005:p 291)
Can be an irritant i given by thisroute
Takes longer to take eect than viaIV route: 1530 minutes
Carcass disposal recommendincineration
Yes, ideallyunless the animalis unconscious,collapsed
Intracardiac (IC) 150mg/kg or both dogs and cats Can be painul i attempted in ullyconscious animals
Carcass disposal recommendincineration
Yes, this route oadministrationis only suitableor unconscious,collapsed animals
Oraladministration(PO)
Dose or neonatal kittens andpuppies: despite discussion withanimal welare groups we havebeen unable to provide suitableguidance on an acceptable doseor oral administration to neonatesat this time.
Dose or sedation o dogs: 63mg/kg(Ramsay and Wetzel, 1998)
Takes longer to take eect than viaIV route
Powdered preparation delivered in
gelatine capsules can be hiddenin ood and is less likely to bedetected by dogs than mixing theliquid orm with ood.
Highly variable time to take eecteven in dogs given the same dose.
Prolonged time to take eect:3090 minutes.
No
Anaestheticagents given asan overdose.
Thiopentone
Proprool
Intravenous (IV) Given to eect Eective dose is highly variable,dependent upon the animalsage, physical status and use opre-euthanasia drugs
This method is time consumingand costly in comparison to othermethods
Carcass disposal recommendincineration
Not unlessthe animal isractious, asthese agentsshould be given
intravenously
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ANN
EX1
Eutha
nasiaagent
Route
ofad
ministra
tion
Dosag
eRe
marks
Us
eofpre-e
uthana
sia
drugsind
icated?
T61(embutramide,mebezoniumiodine, tetracainehydrochloride)ater sedation
Intravenous (IV) Dogs and cats: 0.3ml/kg Slow, steady rate o injectionrequired
Commercially available as apre-prepared euthanasia solutionaccept in the USA
Carcass disposal recommendincineration
Yes, shouldbe sedated toensure slowinjection rate
Potassium
chloride (KCl)ater anaesthesia
Intravenous (IV)
or
intracardiac (IC)
One proposed dosage schedule
is 100g o KCI dissolved in 1 litreo water; 2030ml o solutionsucient or euthanasia o dogsweighing 1520kg
12 mmol/kg o body weight willcause cardiac arrest (Beaver etal., 2001)
Oten available commercially as
a powder which is made into aninjectable solution by dissolvingin water
Carcass disposal recommend
incineration
Yes, must be
anaesthetised
Magnesiumsulphate (MgSO4)ater anaesthesia
Intravenous (IV)
or
intracardiac (IC)
Saturated solution o MgSO4. Oneproposed dosage schedule is:
83% solution o MgSO4 dissolvedin boiling water:
Dosage varies little i given byIV or IC route o administration(Avariez and Caday, 1958).
But highly variable dose orindividuals; one suggestedpublished eective dose:
2038 ml or a 15 kg dog (Avariezand Caday, 1958).
80mg/kg dose (Close et al., 1996)
Saturated aqueous solution1g/ml at a dose o2.54.0 mg/kg (Carding, 1977)
Oten available commercially asa powder, which is made into aninjectable solution by dissolvingin water
Saturated solution becomes veryviscous
Large volumes required to achieve
euthanasia
Carcass disposal recommendincineration
Yes, must beanaesthetised
Gaseousanaestheticse.g. Halothane,Enfurane,
Isofurane,Sevofurane,Desfurane andMethoxyfurane
Inhalation Given to eect
Delivered in a carrier gas (usuallyoxygen) at the minimum alveolarconcentration (MAC)
Only suitable or small animals oranimals already anaesthetised orsurgery
Requires an anaesthetic chamber
or can be delivered via breathingsystems and masks applied tothe ace
Human health hazard i inhaled
Carcass disposal recommendincineration
Not suitableor use inlarger animalsunless already
anaesthetisedor surgery and,on humanegrounds, theyare not permittedto regainconsciousness
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ANNEX
2
ANNEX 2: Guidelines on the intravenous injection o
Pentobarbitone or the euthanasia o dogs and cats
and specialist capture and restraint equipment to prevent
handlers being bitten and to minimise human contact
with animal body uids. To acilitate sae handling o
these animals, sufcient sedation (pages 1314) should
be used prior to injection with the euthanasia agent.
5. Assessment o the animals temperament
and ease o handlingAnimals that are not used to being handled by humans
may experience ear when placed in novel surroundings,which may result in them showing deensive or avoidancebehaviour. Any animals that are likely to be ractious ordicult to handle may pose a risk to personnel through
aggressive behaviour. In these instances it is both morehumane and saer or these animals to be sedated priorto euthanasia with sucient time being allowed or the
sedative to take maximum eect beore euthanasia isundertaken.
Some nervous and aggressive dogs may require muzzlingto avoid danger to handlers. I no muzzle is available,a bandage tied around the dogs nose and then behind
the head (also known as a tape muzzle) can work in theshort term.
Feral cats require special consideration as they aregenerally extremely earul o humans. This presentsboth a welare concern or the cat and a saety concernor the handlers, as the cats deensive-aggressive
behaviour can infict injury. The most satisactorymethod o capturing a eral cat is to use a cat trap with asqueeze back acility (Figure 1). The captured cat is then
pressed against the mesh on the side o the cage so thatan injection o a pre-euthanasia agent (pages 1314) canbe given. Once suitably sedated/immobilised the cat can
be handled saely.
6. Materials
The ollowing materials are required or intravenous
injection:
Syringes
Disposablesyringeswitheccentric(i.e.off-centre)
nozzles. Forcats,asyringesizeof2mlisrecommended.
Fordogs,syringesizesof5,10and20mlwillbe
suitable or most weights.
Disposable needles
Needlediameterismeasuredbythegauge:the
larger the gauge the ner the needle. Needlesareusuallysuppliedindifferentcoloured
containers according to gauge or easy identication.The size o the needle depends upon the size o theanimal and the substance to be injected. For an
Introduction
The World Society or the Protection o Animals stronglyrecommends the use o Pentobarbitone (also sometimescalled Pentobarbitone sodium or sodium pentobarbital);
a barbiturate specically ormulated or euthanasia.The intravenous (IV) injection o Pentobarbitone 20%solution is regarded as the most humane method
o euthanasia or dogs and cats. The method ointravenous injection or dogs and cats can be mastered
easily with training. In most cases animals showlittle or no resistance, provided that they are handledconsiderately and that they are used to close humancontact. In certain countries euthanasia by intravenous
injection may only be perormed by a veterinarian or byoperators working under veterinary supervision.
1. Personnel
Trained, competent and considerate personnel areessential or the humane handling o animals or
euthanasia.
A minimum o two people are required or intravenous
injection: one person should be able to restrain theanimal saely and humanely (reerred to hereater asthe assistant), while the second accurately delivers
the intravenous injection or euthanasia (reerred tohereater as the operator).
2. Preparation
Appropriate preparation must be made or smoothinduction, and to ensure sae and humane handling o
animals or euthanasia. In the rst instance, personnelshould ensure that all materials are available to handand the environment is suitable, as ollows.
3. The environment
A quiet room away rom other animals is required inorder to avoid dogs and cats becoming excited beorethe procedure, which would make them dicult tohandle, requiring additional restraint.
An examination table approximately 90cm in height,with a non-slip surace, acilitates handling and allows
or accurate injection.
Good lighting o the area is essential to enable the
operator to see the site o the injection (usually thecephalic vein on the animals oreleg); thereoreacilitating precise delivery o the injection.
4. Special precautions should be taken orsuspect rabid animalsExtreme care should be taken when handling and
euthanasing animals suspected o having rabies. Special
precautions include protective clothing or personnel,
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26
ANNEX
2
intravenous injection o Pentobarbitone the ollowing
are recommended: Cats: needle o 2224 gauge andlength 0.75 inches (2cm), Dogs: needle o 1822gauge and length 1 inch (2.5 cm) is convenient or
most size o dog.
Cannulae
I permanent plastic cannulae are available or use theyare preerable as they minimise the risk that the needlemay slip during the procedure resulting in some or all o
the drug not being delivered directly into the vein (seesection 7e). The technique or inserting a plastic cannulais similar to that or giving an intravenous injection, but
may take a little more training and practice; insertion isespecially dicult in smaller dogs and cats.
Euthanasia agent
Injection o Pentobarbitone, 20% solution is consideredas best practice; however some euthanasia products
have been combined with a local anaesthetic agentor Phenytoin. The pharmacological dierences are
inconsequential but such compounds may be moreeasily obtained in some countries.
Dose rate
Where possible the animal should be weighed. I this
is not possible, experienced personnel may be able toestimate the animals weight with sucient accuracy.The dose o Pentobarbitone should be determined
according to the manuacturers instructions.
7. Method
(a) Filling the syringe
A new, disposable needle should be attached to thenozzle o a new, disposable syringe, and then inserted
into the bottle containing Pentobarbitone or lling.To prevent a vacuum orming in the bottle, resultingin diculty with subsequent withdrawal o fuid, it isadvisable rst to inject into the bottle an amount o air
equal to the volume o liquid to be withdrawn. Fill the
syringe with the correct dose, calculated according tothe manuacturers instructions or the animals weight.Remove the needle and syringe rom the bottle and
replace the cap on the needle or saety.
(b) Handling and restraint
Dogs
Gently lit the animal on to the examination table. Thedog should be acing the operator who will be giving
the intravenous injection. Large or ractious dogs mayrequire more than one handler or restraint. I theoperator is right handed, the assistant should stand
on the animals let. Where possible the animal shouldbe in the sitting or lying position. The assistants armpasses over the back o the and the other arm holds the
animal under the chin (Figure 2).
Cats
The cat should be gently placed onto the examination
table, acing the operator or intravenous injection. The
assistant should hold the cat against their body, makingthe cat eel secure.
The animals head should be held under its chin withone o the assistants hands, while the other hand
raises the cephalic vein (Figure 3). The cats orelegshould be pushed orward at the elbow, and the thumband orenger used to apply gentle tourniquet pressure,
as described or dogs in Figure 4.
(c) Site o injection
The cephalic vein in the animals oreleg is the mostconvenient site or intravenous injection. When theanimal is held correctly the cephalic vein is visible
on top o the oreleg (Figure 4). Once the animal hasbeen suitably restrained, it may be necessary to aidvisualisation o the vein, particularly in cats and small
dogs, to clip a small amount o hair on the orelegwhere the injection is to be given.
Figure 1.
Photograph o a squeeze-back cage or use with