3 Flashcards
Why is induction of anaesthesia in pigs w/ CO2 and/or anoxia classified as killing and not stunning?
It takes between 10 and 15 seconds, therefore it is not immediate in action and does not meet UK criteria for stunning.
Must leave pig exposed to gas long enough to ensure it is killed.
Gas used to kill?
CO2 at high concentration (80%).
CO2 (up to 40%) associated w/ inert gases (argon or nitrogen).
Inert gases - argon or nitrogen (most welfare-friendly).
– argon easy to control.
Describe gaseous method of killing using CO2 at high concentration.
Direct or progressive exposure of conscious animals to a gas mixture containing more than 40% (minimum 80% for pigs) CO2.
May be used in pits, tunnels, containers or buildings previously sealed.
Simple stunning in case of slaughter of pigs.
Conditions of use of CO2 at high concentrations?
Pigs, mustelids, chinchillas, poultry except ducks and geese (diving reflex).
Slaughter only for pigs.
Other situations than slaughter for poultry, mustelids, chinchillas, pigs.
Description of using inert gases used to kill?
Direct or progressive exposure of conscious animals to an inert gas mixture such as argon or nitrogen leading to anoxia. May be used in pits, tunnels, containers or in buildings previously sealed.
Simple stunning in case of slaughter of pigs.
Conditions of use of inert gases?
Pigs and poultry.
Slaughter, depopulation and other situations.
- Why CO2?
- Problems w/ CO2.
- Cheap.
1.5x heavier than air - easy to control in one place.
Handling prior to stun and kill much better.
Acidic gas so dissolves in water to form carbonic acid - killer. - Pungent to inhale.
Produces respiratory distress.
Effect of CO2 on neural tissue.
Inhalation of CO2 induces respiratory and metabolic acidosis and hence, reduces pH of CSF and neurons thereby exerting its neuronal inhibitory and anaesthetic effects.
Effect on brain and spinal cord at same time so do not kick once unconscious.
CSF pH.
7.4 = normal.
7.1 = analgesia.
6.8 = anaesthesia.
- What is an anoxic environment?
- What is anoxia?
- An atmosphere that contains less than 2% oxygen.
- The physiological response to an oxygen depleted environment.
- in this case, w/ sufficient exposure to a gas or gas mixture to cause unconsciousness and death.
Why is CO2 not used for stunning of cattle and sheep.
Cattle are so big that they destroy the equipment when they panic.
Sheep take in CO2 in their wool in container of gas and then expel it when come out and knock handlers unconscious.
Legislation regarding bleeding to kill?
A person engaged in bleeding or pithing of an animal which has been simple stunned must ensure the animal is bled or pithed w/o delay after it has been simple stunned.
If an animal is bled after simple stunning, no person may cause or permit any further dressing or any electrical stimulation to be performed on the animal before the bleeding has ended and in any event not before expiry of:
- 30 seconds post-bleed for bovine.
- 20 seconds post-bleed for all other animals.
Effect of bleeding on the animal?
Loss of oxygenated blood due to loss of BP causes brain anoxia, increase in acidity and neuronal and cortical brain death.
No metabolites removed from the brain causes brain death.
Is a beating heart required to ensure blood is lost at exsanguination?
No.
Blood is lost through gravity.
Sheep bleeding method?
Full ventral neck cut, back to the spine.
Cuts both jugular veins and both carotid arteries.
Causes brain death in a maximum of 14 seconds.
- If only one side cut for some reason, takes 70 seconds to brain death.
- If only jugular veins cut for some reason, takes nearly 5 mins.
Pig bleeding method?
Thoracic stick.
Cuts major vessels around the heart, releasing large volume of blood:
- cut heart, brachiocephalic trunk, aorta, subclavian artery.
BP falls quickly, starting process of brain death.
Need to make cut as big as possible as pigs can squeeze and close cut and recover.
- if see pig start to recover during bleeding, shoot immediately, cut again.
Achieve brain death in 18 seconds.
Cattle bleeding method.
Thoracic stick.
Cut skin w/ one knife and w/ another knife, cut the vessels in the thoracic cavity.
Cut heart, brachiocephalic trunk, aorta, subclavian artery.
Sometimes spinal reflex leg lift to cutting.
Brain death in 17 seconds.
- if not killed already by captive bolt.
Stun-to-stick times.
Cattle = 60 seconds.
Pigs and sheep = 15 seconds.
*all based on worst case scenarios.
