Euthanasia Flashcards
Euthanasia
goal of ending life of individual animal in way that minimizes or eliminates pain and distress
Humane Slaughter
processes, methods employed to intentionally kill animals raised for food, fur, or fiber production
o Applies to individual animals killed on farm, commercial production processes
o Includes transport, handling to time of death when ready to enter food chain
Depopulation
rapid destruction of large numbers of animals in response to emergencies, such as the control of catastrophic infectious diseases, or exigent situations caused by natural or human disasters
o Extenuating circumstances
o Large numbers of animals quickly, efficiently destroyed
o As much consideration for welfare as possible
Two Laws that Federally Codify Humane Slaughter for Cattle, Calves, Horses, Mules, Sheep, Swine?
1958 Humane Slaughter Act
1978 Humane Methods of Livestock Slaughter Act
Acceptable Methods
consistently produce a humane death when used alone or as the sole means of producing death
Acceptable with conditions
require certain conditions to be met to produce humane death consistently
o May have greater potential for operator error or safety hazard,
o Not well documented in the scientific literature
o May require a secondary method to ensure death
Unacceptable Methods of Euthanasia
inhumane under any conditions or pose a substantial risk to the human applying the technique
Unacceptable Methods of Euthanasia: Anesthetics
choral hydrate
chloroform
diethyl ether
NMBAs in consciousness vertebrate animals
Unacceptable Methods of Euthanasia: Chemicals
cyanide, formaldehyde, household products, solvents, cleaning products and disinfectants, strychnine
Unacceptable Methods of Euthanasia: Physical Methods
air embolism, asphyxiation, burning, rapid decompression, drowning, exsanguination, hypothermia, manually applied blunt force trauma to head, non-penetrating captive bolts, rapid freezing*, smothering, thoracic compression
What are the exceptions to manual blunt force trauma?
piglets, chickens, small laboratory animals
Unacceptable Methods of Euthanasia: other agents
insulin, MgSO4 (adjunctive or under GA), KCl (adjunctive or under GA)
What are the exceptions to NPCB?
piglets, chickens; lambs, kids with adjunctive
What are the exceptions to rapid freezing?
reptiles, amphibians <4g, <5d rodent neonates (7 per 2020)
Adjunctives for Euthanasia
practices not used as sole or primary method but can be used in conjunction with acceptable methods following initial loss of consciousness
exsanguination, pithing, intravenous or intracardiac magnesium sulfate or KCL, creation of pneumothorax
Depopulation: preferred
Utilized preferentially when circumstances allow implementation
Depopulation: Permitted in constrained circumstances
Only when circumstances constrain ability to reasonably implement a preferred method
Depopulation: Not Recommended
Only when circumstances preclude reasonable implementation of any of preferred methods or those permitted in constrained circumstances
AND when risk of doing nothing at all deemed likely to have a reasonable chance of resulting in significant more animal suffering than proposed depopulation technique
Animals: Loss of Consciousness
loss of rightening reflex (LORR), AKA loss of position (LOP)
* Should always precede loss of muscle movement
* Easily observable
* Applies to wide variety of species
* Integrated whole animal response
Physical Methods of Euthanasia: MOA
Instantaneous unconsciousness by destroying, or rendering non‐functional brain regions responsible for cortical integration
Death quickly follows when midbrain centers controlling respiration and cardiac activity fail
Often followed by adjunctive methods (exsanguination or pithing) to ensure death
Advantages of Physical Euthanasia Methods
Instantaneous unconsciousness
Inexpensive, humane, painless if performed properly
Leave no drug residues
Animals presumably experience less fear, anxiety DT little preparatory handling
Disadvantages of Physical Euthanasia Methods
Usually involves more direct physical proximity by people
More offensive and upsetting for operator
Decapitation, cervical killing:
electrical activity in brain can persist <30s
Unclear when unconscious develops
Inhaled: acute hypercapnia
> 5% atmospheric CO2 – killing DT hypoxia
* Rapidly reduces intracellular pH, producing unconsciousness, reversible anesthetic state
* Reduction of both basal and evoked neural activities
* Inhibition of central N-methyl-D-aspartate (NMDA) receptors
* Does not rely on induction of hypoxia to cause unconsciousness, death
Additional of Nitrous Oxide to Inhaled Euthanasia Techniques
N2O with CO2: Displacement rate faster than CO2 alone
* Displacement rate of 20, 60% of chamber volume per minute, produced LORR in mice 10.3% faster than CO2 alone
General Recommendations for CO2
gradual displacement rate between 10-30% of container volume per minute
Based on time constants: When starting from gas concentration near 0, one time constant required to reach washed in concentration 63 volume percent
o Ex: gas volume displacement rate of 20% per minute represents time constant of 5 minutes (1/0.2)
Inhaled Techniques: Hypoxia
MOA: direct via displacement of O2 with inert gas/low Patm, indirect via CO or exsanguination
Exposure to high concentrations of inert gases, such as nitrogen or argon
To be effective, O2 levels of <2% must be achieved and maintained
O2 of >6% prior to death allows immediate recovery
Ex: CO, exsanguination, low atmospheric pressure stunning of poultry (LAPS) in poultry
Limitations of Hypoxia Techniques for Euthanasia
Not appropriate for species or stages of development that are tolerant to prolonged periods of hypoxemia
Advantages of Inhaled techniques for euthanasia
Minimizes operator contact
Individuals or groups
Able to be scaled
Not DEA controlled substances
Disadvantages of Inhaled techniques for euthanasia
Unconsciousness not immediate
Most inhaled methods aversive to animals, humans
Worker protections necessary
Volatile Agents as Euthanasia
Halothane – least aversive of inhalants, more aversion with increased concentration
large amounts absorbed, significant amounts remain in the body for days even after apparent recovery
unsuitable for euthanasia of food producing animals
CO2 Exposure as Euthanasia
using gradual fill methods less likely to cause pain due to nociceptor activation by carbonic acid prior to onset of unconsciousness
Recommendation: CO2 displacement rate between 10 and 30% of chamber volume per minute
* At these rates, unconsciousness occurs prior to exposure to CO2 levels known to produce nociceptor stimulation
Aversion Assoc with Nitrogen, Argon
Aversion depends largely on species, conditions of administration
Hypoxia from exposure to these gases aversive to laboratory rodents
Not directly aversive to poultry, swine: hypoxia appears non inversive
Euthanasia: CAS
commercial controlled atmosphere stunning processes for stunning of poultry and hogs
Gradual introduction to CAS atmospheres
3 MOA
* Physical transport at controlled rate into contained stunning atmospheric gradient
* Controlled induction of stunning gases into enclosed space
* Controlled reduction of atmospheric pressure to produce hypoxia
Fetal Sentience and Euthanasia
- Observation of fetal body, respiratory movements = part of normal fetal physiology in utero - should not be a cause of welfare concern
To feel pain: have adequate neural development for sensory perception, must be in awake conscious state
All mammalian embryos or fetuses studied to date remain in an unconscious state throughout pregnancy and birth
Isoelectric EEG, which is incompatible with consciousness, rapidly appears after cessation of maternal oxygen supply
LAPS
Low Atmosphere Pressure Stunning
- Stunning poultry prior to humane slaughter
- MOA: Gradual reduction of barometric pressure due to hypoxia
Negative atmospheric pressure applied gradually over time, typically over 1min in broilers: results in acute hypoxic state not unlike being in an unpressurized airplane at altitude
Targets with LAPS
Atmospheric pressure =156 mmHg
Inspired PO2 = 33 mmHg = 4% oxygen atmosphere at sea level
target pressures for broilers achieved within 1’ from start of LAPS cycle maintained for 4’40s to assure recovery to consciousness does not occur prior to exsanguination
Advantages of LAPS
o Elimination of welfare issues associated with dumping live birds onto conveyor line
o Eliminating the need to handle live birds manually
o No hemorrhagic lesions
o Low to no risk of gas expansion in enclosed spaces
o Corticosteroid concentrations in LAPS stunned broilers nearly half those observed in electrically stunned birds, HR decrease over time
Rapid Decompression Vs LAPS
LAPS = gradual
Rapid decompression = Unacceptable for euthanasia
o Causes pain, distress through expansion of gases present in enclosed spaces
o Hemorrhagic lesions in lungs, brain, heart
Foam Depopulation
MOA: medium or high expansion foam generating equipment to create a blanket of water based foam to cover the animals
o Most current equipment uses compressed air ambient air to create bubbles
o Immersion in foam produces rapid airway blockage, occlusion: death by suffocation
* Water-based foam requires less time to death than CO2 gas, with similar pretreatment and post-mortem corticosterone levels
