TECHNOLOGICAL HYGIENE OF
SWINE AND CATTLE SLAUGHTER
1. HUMANE SLAUGHTER
 Aims, legislation
- to cause the minimum stress to the animal
- acceptable or unacceptable ways of killing
- duty of the official veterinarian
- humane slaughter laws in effect for many years (93/119/EC on
the Protection of Animals at the Time of Slaughter and Killing)
- main requirement: the animal be rendered unconscious before
being bled (except in Jewish and Muslim methods)  slaughter
two-stage process: stunning and subsequent bleeding
 Pre-slaughter handling/restraint
-
resting, fasting, spraying
- delivering the animals to the point of slaughter
 to reduce to a minimum the fear and apprehension felt by
the animals (walkways, electric goads, stunning box)
- effect of pre-slaughter stress on meat quality
 Stunning
- purposes: to induce immediate insensibility (unconsciousness and analgesia);
to produce sufficient immobility  to facilitate
sticking; to initiate bleeding
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- methods of stunning
1. Mechanical stunning
- mainly in cattle and sheep (pigs excessive convulsions)
- two types of devices
 invasive captive bolt (pistol)  driven through the
skull into the brain  invasive damage of the cortex
and the midbrain  unconsciousness
site for shooting (see figure)
 non-invasive captive bolt (knocker)  when hits the
skull  stuns the animal  mostly used when brains
are collected for edible use
2. Electrical stunning
- passing a 50 Hz electrical current through the
brain  immediate epilepsy due to over-excitation of
the brain’s neurons (20-70 s) + analgesia (5-15 min)
(see figure)
- mainly used for pigs (calves, sheep)
- positioning of the electrodes  current pass
through the thalamus and cortex (head-only system) 
mostly used
- head to back stunning  brain anesthetised +
cardiac arrest  brain function ceases
 animal is
killed  stunning to sticking interval less important
(within 3 min  satisfactory bleeding)
- low ( 150 V) or high-voltage ( 300 V) systems
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3. Carbon dioxide stunning
- commonly for pigs
- animals passed through a well with CO2 and air
atmosphere
-
legally
min.
70%
CO2 required,
but
85-90%
is
recommended
- period of exposure 45 s
- bleeding within 30 s after leaving the gas chamber
- acidification of the CFS  pH 7.4  pH 6.8
- different types of apparatus used
- advantages: less laborous, better relaxation  easier
dehairing and dressing, higher efficiency of bleeding, less
muscular haemorrhages; lowest incidence of PSE
 Bleeding (exsanguination)
- the only procedure that must be assumed to cause death of the
animal (none of the stunning methods)
- should occur within 15-30 s of stunning
- objective: to remove the blood as completely and rapidly as
possible  blood ideal medium for multiplication of bacteria
- about 40-60% of the total volume is removed during bleeding 
remainder in the viscera (3-5% in muscles)
- cattle: after stunning the animal is hoisted (by shackling of a
hind leg over a bleeding gully), then the skin is incised along the
jugular furrow with one knife  2. knife is used to sever the
aorta in the thoracic cavity  knives should be sterilised
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between each incision!  bleeding should be continued for 6
min.  average blood obtained: 13.5 litres
- sheep: incision in the jugular furrow close to the head 
severing the carotid arteries (jugular veins, trachea, oesophagus
 contamination with ruminal content)  bleeding for min. 5
min; amount of blood about 2 litres
- pigs: knife inserted in the midline of neck in the depression in
front of the sternum  carotid arteries and jugular vein severed
at the entrance of the chest; not to insert the knife too far 
penetrate into the shoulder  blood and water from the scalding
tank back into the shoulder “pocket” beneath the scapula  wall
“cooked”; bleeding for min. 6 min, amount of blood 2-4 litres
 Ritual slaughter
- legislation allows slaughter without previous stunning in Jewish
and Islamic or Muslim methods, resp.
- Jewish slaughter (Shechita)
 at slaughter the animal must be alive, healthy and suffered
no injury  prior stunning forbidden
 a swift cut across the neck with a very sharp knife 
severing
the
skin,
underlying
muscles,
trachea,
oesophagus, jugular veins, carotid arteries
 five principles: neck should be cut without pause, pressure,
stabbing, slanting or tearing
 if knife receives any nick during operation  animal is unfit
for Jewish consumption
 “searching”: when diaphragm is exposed during dressing
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 the cutter (shochet) pierces this  thoracic organs
manual examination
 carcass fit or “Kosher”  meat porged by removal of the
blood vessels and sinews  only forequarters normally
used (hindquartes contain over 50 blood vessels can only
be porged by highly skilled kosher butchers  rarely eaten)
- Muslim methods (Halal)
 similar to the Jewish but there are no searching or porging
 both fore- and hindquartes are eaten
2.
MAIN
TECHNOLOGICAL
STEPS
OF
SWINE
AND
CATTLE
SLAUGHTER
 SWINE SLAUGHTER
- Stunning

electrical

CO2
- Bleeeding

incision at an angle of about 45o, 5 cm in front of the
breastbone down towards the jaw with the knife penetrating to a
depth of 12-15 cm

thorough bleeding  hog shall hang on the bleeding rail for
min. 6 min  muscles relax + hair is more readily removed
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- Scalding
 Horisontal scalding vat or tank: carcass is agitated in scalding
water (60-63oC) for about 5-10 min  scurf and hair loosened
 easier to remove
 temperature of scalding water (too hot  skin cooked + hair
becomes set; too cool  surf and hair not loosened)
 cleaning of the vat, supply of water
 Vertical: steam is applied while the animal still on the
overhead rail. Lower temperature of 41 °C. Much more
hygienic, lung contamination is also reduced, dehairing is
easier, lower operation cost, practically no PSE manifestation
- Dehairing (depilation)

dehairing machine: loosened hair and scurf are removed by
friction produced by blades/rods (or by hand) while the carcass
is revolved

spraying with hot water

remaining hooves removed
- Singeing
 singeing furnace: skin is scorched at 800-1000oC for some
seconds  to dry and harden the skin + to decrease bacterial
load of the surface (usually 10/cm2)
- Scraping and polishing
 “black” scraping: removal of any burned (black) parts by
metal blades
 polishing equipment: final cleaning of the entire surface with
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plastic blades and brushes
- Eviscerating
 in the clean part of the abattoir not later than 45 min after
stunning
 rectum is loosened and ligated  to avoid contamination
 carcass is opened by a longitudinal incision along the median
line from the pelvic region to the neck
 urinary bladder, uterus, penis removed  inedible
 gastro-intestinal tract and the pluck removed together and
intact  special care to avoid cutting into them + to avoid
contamination from the floor
 detached organs must be identified to enable them to be
recognised as belonging to a given carcase  moving parallel
- Splitting
 Body is mechanically cut into two parts-halved: 2 carcases
obtained
- Post-mortem inspection
 splitted carcases + detached offals
 sampling for trichinella investigation
 suspect carcases  separated and more detailed examination
suspect cooler until supplementer
laboratory investigations completed
- Trimming
 removal of the ears, eyes + abdominal fat
 cleaning of the abdominal cavity
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- Quality testing
 pH, thickness of fat and meat  classification
 marking
- Chilling

 7o C
- Preparation of offals

red offals: separation of parts of the pluck

edible parts chilled  3oC

packaging

green offals: separation of the stomach from the guts,
contents removed edible parts thoroughly cleansed,
mucosa removed
- Transporting
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 CATTLE SLAUGHTER
-
Stunning
 mechanical
 recently electronarcosis
- Bleeding
 2-stage procedure using 2 knives
 cuts by the spear cut technique  blade of the knife
reversed  cut from the inside of the skin towards the
outside
 short initial cut  first knife moves from the dirty exterior
towards the clean interior  knife washed and sterilised 
Second knife for section of blood vessels
- Skinning
 removal of the udder
 skinning of the hind quarters, removal of hindlegs
 ligature of the rectum, removal of the penis
 skinning of the abdomen – by 2 operators, each for one side
 removal of the forelegs
 final dehiding
 removal of the head – before sectioned oesophagues
ligated  rodding
 dressing of the head – with pressurized water
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- Eviscerating
 sealing the rectum (bunging) – with a plastic bag and rubber
ring
or
elastic
band
(manually or by a special
machine)
 stomach and guts severed from their natural connections
and removed
 red offals removed by a different operator
- Splitting the carcases
 machine (saw) to be cleaned and sterilised  distance
between carcases
- Post-mortem inspection
- Washing of the carcases
- Chilling
  7o C
- Preparation of red offals
 in a separated room
 separated organs  chilling room   3oC
- Preparation of green offals (stomach)
 in a separated area (stomachs should not be opened before)
 stomach (abomasum) emptied, washed, centrifuged, heated
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3.
TECHNOLOGICAL
HYGIENE
OF
SWINE
AND
CATTLE
SLAUGHTER
 Sources of contamination
- outer integument: hide, hair, fleece or skin
 live
animal:
one
of
the
main
sources
of
carcase
contamination
 essential: livestock be presented for slaughter as clean and
dry as possible  hygiene on the farm, in transport lorries,
in meat plant lairages
- gastrointestinal tract
 spillage from the rectum and oesophagus
 accidental puncture of the stomach and intestines
 mixed bacterial flora of the GI may reach 1010 cfu/g
- sticking point
 during sticking: bacteria, bloodstream  organs
- physical contact with structures
 design of line: legs, necks, heads do not touch with stands,
floor, tables
 gross cleaning: must be ongoing throughout the working
day  to prevent build-up of blood and debris
 during breaks: to rinse down the line and slaughter-floor
- operatives
 workers: important, mobile source of contamination
 movement of personnel: strictly controlled, ideally from the
clean  dirtier parts
 upgrade stations: washing, disinfection. change of clothes
 staff training programme: enabling workers to comlpy with
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conditions of hygienic production  official veterinarian
must be involved
- equipment and utensils
 knives, saws, hockcutters: direct contact with meat 
regularly cleaned and disinfected
 moving overhead line, hide–puller: indirect sources of dirt,
debris  oil, grease or faeces
- slaughterhall environment
 ventilation:
to
prevent
the
build
up
of
steam
and
condensation  vector for bacteria, moulds +  surface
moisture   bacterial growth
 pressure differences between the workroom and the outside
 draughts when doors left open  flies, dust, dirt
 poorly maintained structures: contamination source (rust,
paint flakes)
- vermin
 physical exclusion: fence around the premises (dogs, cats)
fly-screening on windows
 killing: rodents, flies
- chemical contamination
 cleaning chemicals: contamination of the meat if not rinsed
of the structures correctly
 storage
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 Methods of reducing contamination
- dealing with the dirty animal
 rejection without slaughtering
 slaughter delayed  resting  animals become dry
 showering
 slaughter separated in time or place
 line speed decreased  time for extra washing of hands,
arms, sterilising equipment
- protecting the meat from the worker
 clothing:
clean/easily
cleanable
headgear,
footwear,
working clothes + other protective clothing; laundry
facilities
 hands:
facilities to wash hands
water temperature (too cold, too hot)
non-hand-operated outlet (by foot, magic eye)
bactericidal soap
 gloves: mostly become contaminated from the hide with
faeces, soil  impossible to wash the entire length 
wearing of gloves presents a dichotomy between hygiene
and health
 medical certification: pre-employement and routine medical
examination; self-declaration
- basic hygienic techniques
 hygienic use of knives: cleaning and sterilisation 
washing  82oC water for min. 2 min.; multiple knife
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technique  each spends the maximum possible period
in the steriliser
 hygienic use of scabbard: necessary for transportation of
knives to work-station  all knives to be unloaded into the
steriliser
 hygienic use of steel: used to keep the knife sharp  at the
beginning of the operation  sterilised  stored hanging
and only sterilised knives to be used on it
- layout and flowlines
 layout of the slaughter floor and flowlines for entry and exit
of carcases, operatives, equipment  properly designed
 clear separation of clean and dirty parts
 walkways  without risk of contamination on the lines or
through less fit parts (green offal room, rendering plants,
waste storage areas)
 cross-contamination during breaks
 waste bins + hide conveyor  never cross the slaughter line
 risk of contamination
 site of washing and sanitising equipment  easy to use 
good design
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4. ASSESSING OPERATIONAL HYGIENE
 Traditional quality control systems
- regular inspections of the hygiene of structures and equipment
based on a check list
- standards laid down in codes of practice  GMP, directives,
decisions etc.
- identifying the problems only after they have occured
- increased demand for more proactive systems
 HACCP
 Hazard Analysis Critical Control Points
- general term
- HACCP in the meat plants
- main subsequent steps
 hazard analysis (hazards, severity, risk)
 critical control points (CCP1, CCP2)
 specification of criteria (specific limits of physical,
chemical or biological characteristics; quantitative)
 monitoring system (systematic checking at the CCPs;
selection of methods  immediate result  traditional
microbial checks  rapid analytical methods  ATP
bioluminescence assay
 corrective action (immediate action)
 verification (systematically by the quality assurance staff
and the veterinary inspection team; statistically significant
frequency; end products, structures, equipments)
 documentation
- main CCP-s of swine and cattle slaughter (see figure)