Slaughter of animals
29 important questions on Slaughter of animals
How are animals been handled up to the point of stunning? [ante-mortem inspection]
- Held in special pens/areas in large
- Animals rest & calm down --> fatigued/stressed by transport/uploading
- easier handling
- improve quality
- improve welfare
- Animals to rest adequately in unmixed groups (less stress)
- stressed = more likely to be fractious, fall/bruise, danger to personnel handling them
- Poultry transported in crates --> makes it impossible to provide food/water
- Minimise lairage time
What is ante-mortem inspection?
- Animals are inspected before slaughtered
- Identification of clinical signs of diseases
- Identification of pharmacological agents given / injuries
What can be looked for when doing an ante-mortem inspection
- It is vital to detect some diseases early --> prevent further infection & contamination
- e.g. Anthrax
- e.g. Foot-and-mouth disease
- Traceability (important - diseases)
- Cleanliness (risk of carcass contamination)
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What is the foot-and-mouth disease
- Virus = relatively hardly & highly infectious (rarely fatal)
- Extremely rare that humans catch it
- Reduced productivity (poor growth/less milk/abortions) --- economically serious
Name the 3 main types of methods used for stunning
- Use of mechanical instrument (e.g. Captive bolt pistol)
- Electrical current passed through brain
- Immersion in anaesthetic gas (e.g. CO2)
Which animal species are typically stunned by each type?
[mechanical, electrical, anaesthetic gas]
Electrical
- Poulty, pigs & sheep
When is a free bullet used?
- Generally, only used for large bulls & boars
- Less easy to ensure safety, danger = bullet passing through body & ricocheting
- Necessary if animal has very thick skull to use captive bolt pistol
What can you tell about captive bolt & concussive stunning?
- Methods developed from use of pole-axe
- Modern captive bolt / pneumatic stun gun (beef) much easier to use
- To stun an animal --> not necessary to penetrate brain
- concussion alone effective - some equipment give non-penetrating blow
What is the position of shooting?
- Position of shooting --> maximum damage done to brain
- Brain in different position to head shape --> different positions optimal for different species
- Due to dangers of BSE spread --> captive bolt use in North America ceased
How is stunning/killing with gases go?
- Pigs may be rendered unconscious & killed by CO2 (80-90% by volume)
- Remain in gas for 90 seconds / more (longer =kill rather than stun)
- CO2 = acidic & pungent at concentrations >30%
- Potent respiratory stimulant - gasping & possible respiratory distress
- CO2 works as carbonic acids formed when it dissolves in blood --> reduces pH of cerebra-spinal fluid that surrounds brain -> loses consciousness pH falls <7.1
What type of gas is used for chickens [stunning/killing]
- Anoxia gas
- relatively stress free
- inert gas (argon or nitrogen) - reduce oxygen levels 2% or less
- Tasteless & odourless = not detectable by animals
- Argon's density - easy to confine in chamber
- Duration of unconsciousness after removal not as long as with CO2
- Add 30% CO2 to argon - benefits outweigh pungency perceived
What is the tonic phase and what is the clonic phase
- Effective percussion stunning leads to
- Immediately collapsing
- Stopping rhythmic breathing
- Becoming rigid with head extended
- Eyeball is fixed
- Lasts 10-20 seconds
Clonic phase
- 15-20 sec after stunning
- Kicking /paddling movements
- Not killed by exsanguination - will recover
Rhythmic breathing returns followed by resumption of consciousness
How can you recognise an effective stun
- Amount of clonic convulsions may be reduced by head-to body stunning
- Most reliable & easiest way to recognise effective stunning in sheep, cattle & pigs = end of rhythmic breathing
- Electrical stunning causes disruption of normal electrical activity in brain producing epileptiform (electro-lactic)
- Large increase in release of glutamate & aspartate in sensory cortex (seizure)
- act as neurotransmitters - over excite neurons = seizure
- Characterised by initial tonic phase when animals become rigid, rhythmic breathing ceases & eyeball fixed
Effects of stunning methods on carcass & meat quality
- Percussion stunning
Effects of stunning methods on carcass & meat quality
- Captive bolt stunning
What are the advantages of kill poultry using gas?
- Less haemorrhaging & broken bones
- Birds killed by anoxia show increased pH fall in breast muscle --> less time post-mortem before portioning without risk of muscle shortening = tougher meat
What are the issues concerning religious slaughter? And what are the main religious slaughter methods?
- Shechita used by Jews
- Muslims to produce Halal meat
- Jack used by Sikhs / Hindus
- Shechita & Jatka: animal not stunned prior to killing by exsanguination
- stunning not used in Halal slaughter but some methods may be acceptable to some adherents of Islamic faith
- Shechita & Halal: major vessels of throat severed by transverse cut
- Jatka: animal decapitated with single sword stoke
What is carcass dressing?
- Carcass tissues & inside of body cavities microbiologically sterile
- Skin, cavities, inside of gut contaminated with soil, dirt & bacteria
modern slaughter:
- Animals hung by hind legs from overhead rial system & dressed
- hygiene & throughput
- Production line - each person carries out single job / one purpose
- efficient & helps maintain carcass hygiene - no cross contamination
How goes carcass dressing with cattle & sheep
- Oesophagus tied closed - prevent back flow of rumen contents
- Head & feet removed
- Carcass skinned
- Feet removed below carpals (knee bones) in forelegs & tarsals in hind leg
- Skin can be removed used mechanical hide-pullers (or manually)
How goes carcass dressing with pigs
- Not skinned - except for making leather
- Hair removed by scraping & scalding
- hot water loosens hair & outer layer of skin, then scraped off by passing carcass through revolving metal tipped paddles
- carcasses washed & cleaned with revolving brushes
- Toenails removed
- before washing carcasses may be singed (burn hair & tighten skin)
- Scalding & singeing (burning) to some degree kill bacteria on surface - not sterilised
- Feet left on carcass & head removed at later stage
What are the advantages of carcass dressing done by machines
- Reduces manpower requirements
- Improve carcass hygiene (meat safety)
- Produce better hide & pelt quality
- Higher yield of retail joints
How are chicken carcasses dressed?
- After stunning blood vessels in neck severed = exsanguination
- automatic - knife with rotating blade
- Scalding: remove feathers --> low temp. 30 seconds (<55*C broilers)
- Pucking: feathers removed mechanically by rotating rubbers
How is poultry been processed?
- Evisceration separated from defeathering to reduce carcass contamination
- Skin cut along back of neck & trachea & crop freed
- Abdominal cavity is opened up by incision around vent to enable viscera to be pulled out
- Lunge lie tight under vertebral column & need careful removal
- Head, neck & feet are cut off
- Carcass chilled either in cold air or iced water to 10*C
- Poultry processing now highly mechanized
What is carcass washing?
- After dressing washed with fine water spray to remove surface blood & bone dust
- Effectiveness increased by using hot (80*C) water / by including low concentrations organic acids, chlorine / other agents in water
- Traditional practice of wiping carcasses with cloths = unhygienic
What happens with post-mortem inspection?
Provide a few examples of diseases and/or conditions that can be identified during post-mortem inspections
- Carcass & viscera inspected immediately after slaughter
- ID abnormalities / disease that would make meat & edible offal unit for human consumption
- Important that carcass retain identity with parts & viscera removed from it
- Inspection carried out by specially licensed veterinarians / meat inspectors
- Considerable attention given to lymph nodes to detect disease state
What can be found during a post-mortem inspection?
- Pneumonia & tuberculosis (TB) have characteristic incisions
- Parasitic disease (tapeworms) often manifested in cysts in heart, liver & muscles
- Larval stage of roundworm forms cysts in pool muscle --> consume cause trichinosis
- Larvae of nematode parasite, Ascaris scum, lodge in liver & result in small foci of connective tissue giving rise to milk spot liver
- Inflammation of lining of thoracic or abdominal cavity indicate infection
- Swine erysipelas produces red diamand shaped marks on pig skin
What are the modern production systems:
- Emphasis on presenting only healthy animals for slaughter
- Controlling levels of parasites & infectious diseases - farm
- Risk assessment-based inspection - preventing carcass contamination
What are the most valuable and are edible by-products
- Liver
- Heart
- Tongue
- Kidneys
- Spleen
- Brains
- Blood
- Edible raw fat
- Trotters
- Cattle diaphragm
- Parts stomach &. Intestines
What are the four main categories of by-product?
- Edible by-products (most valuable)
- Skins
- Production of pharmaceuticals ...?
- Animal feed...?
- Value determined by handling
- Most prone to rapid deterioration if handled incorrectly - downgrading
- Critical part of handling = storage at low temperatures
- Fat particularly liable to oxidation & development of rancidity
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