PART SIX: PIG SLAUGHTER
The electric goad
It is legal to use the electric goad on the hindquarters
of adult pigs to force them to move forwards. Pigs find the
slaughterhouse environment extremely distressing and it is
barbaric to use painful electric shocks to move them from
place to place. Viva! believes the electric goad should be
banned (see Cattle slaughter: The electric
It is normal practice to starve pigs in the run up to slaughter.
In their paper entitled "Feeding pigs prior to slaughter",
the Ministry of Agriculture and the Meat and Livestock Commission
explain, "Too much food in the stomach prior to slaughter
is wasteful. It can lead to vomiting and transit deaths and
possible contamination of meat from gut puncture." (46)
Pigs will suffer during the fast period. Researcher NG Gregory
says that when being starved, pigs and other monogastric animals
go through the same phases of hunger as humans. He says, "Initially
there is an enthusiasm for food but with progressive fasting
this changes to a gnawing emptiness whilst feeling weak, lethargic
and sensitive to cold." (30)
Fighting between unfamiliar pigs
When pigs are waiting to be killed, they are often mixed
together with pigs who they are unfamiliar with but who have
similar "live weights". (47)
Researcher PD Warris explains that this disrupts established
hierarchies and often leads to individuals fighting to establish
new dominance orders. The fighting can be severe and lead
to serious injury - at a time when they are already agitated
Warris concludes that, "The only way of completely preventing
fighting is not to mix unfamiliar animals."
Showering pigs in the lairage
When pigs are in the lairage, they are often showered with
cold water in an attempt to cool and calm them down. A 1996
survey reported that approximately 90% of pigs were showered
continuously before they were slaughtered throughout the year.
The researchers say that in the summer showering is likely
to be beneficial to the animals' welfare but that in winter
animal welfare may be "compromised". They say that they have
observed pigs shivering in cold weather when they are in well-ventilated
lairages inside which the air temperature is not controlled.
They conclude that pigs should not be showered continuously
if the temperature inside or outside the lairage falls below
5 degrees centigrade and advise slaughterhouse staff to cease
showering pigs if they are seen to be shivering.
Electric head-only stunning
According to the Meat Hygiene Service, "Fat pigs are slaughtered
in a total of 239 premises and an electric head-only stun
is practised in 204 of these premises. The average stunning
current used for all categories of pig was 1.2 amps." (10)
The efficacy of the head-only electric stun has primarily
been studied on sheep (see Part 4: Sheep Slaughter, page 37).
However, most pigs are also stunned using this technique -
meaning that there is a possibility that pigs are not fully
unconscious at the time of slaughter. Viva! is extremely concerned
about the use of electric head-only stunning on all species.
In addition to the question of whether electrically stunned
pigs are rendered unconscious at all, there are other welfare
i) Inaccurate placement of the electric tongs
Accurate placement of the stunning tongs is essential if
an effective stun is to be achieved. Pigs are supposed to
be stunned between the eyes and the base of their ears on
both sides of the head (49). Pigs stunned electrically will
either approach the stunner on a conveyor belt or will be
standing in groups in a pen. Rough handling, noise and being
penned with pigs who are unfamiliar will leave them in a state
of stress. If they are penned in groups, accurate stunning
is difficult to achieve.
J.M. Sparrey and S.B. Wotton produced a paper on the design
of pig stunning electrodes. They say that, "The accurate placement
of stunning tong electrodes on a pig, for the purpose of electrical
stunning, is a recognised problem for the pig industry. Poor
tong placement could result in poor electrical contact, electrodes
that do not span the brain, an inadequate stun and hence poor
animal welfare at stunning." (50)
In 1993, Anil and McKinstry surveyed tong positioning in
pig abattoirs. They found that 36% of tong placements did
not span the brain as required by law (51). 13.3% of pigs
were stunned on the snout/jaws - a position which a later
study found "should be avoided from a welfare standpoint".
In their 1998 study, they found that 2 out of 13 pigs stunned
on the snout/jaws were not stunned successfully even though
a high current (250V) was used. (49)
16.3 million pigs were slaughtered in the UK in 1998 and
73.9% - or 12 million pigs - were given an electric head-only
stun. Based on the scientists' figures, 1.6 million of these
pigs would have been stunned on the snout/jaws and 244,800
of these pigs would not have been stunned at all. These animals
will have had to endure the pain of a severe electric shock
and will then have been stunned again or simply shackled up
and knifed whilst conscious.
ii) Electrodes penetrate the skin
Electric tongs for use with high voltage systems use dry
electrodes with sharp, teeth like contacts which usually penetrate
the skin (50). Pigs' skin has a great deal of resistance to
an electric current and therefore an electric stun is more
likely to be effective if the skin is penetrated by the electrodes.
However, if a pig is not immediately stunned or the tongs
need to be removed s/he will have been fully aware of the
skin on the sides of his or her head being pierced by sharp
metal teeth. This is likely to be a particular difficulty
with the introduction of the "fail-safe" device.
This device (not yet commercially available) enables the
operator to position the electrodes on a pig's head and test
whether sufficient current is available to achieve an effective
stun. If insufficient current is available, the system will
be disabled and the operator has to try again.
Sparrey and Wotton conclude that there is potential for improvement
in the design of pig stunning electrodes (50).
iii) Pigs regain consciousness
In order to calculate whether electrically stunned pigs are
regaining consciousness in abattoirs, we need to look at the
length of time a stun lasts for and compare this to the time
duration between stunning and knifing and the length of time
it then takes for a pig to lose brain responsiveness.
Pigs stay unconscious for an average of 42 seconds (49).
They take up to 23 seconds to lose brain responsiveness when
the major vessels near the heart are severed (52). This means
that the stunning to knifing interval should not be longer
than 19 seconds. Even this would be too long as some pigs
will not stay unconscious for 42 seconds.
The MHS Animal Welfare Survey reveals that stun to knife
intervals in UK abattoirs range between 0 and 180 seconds
(10). They explain that the longer stun-to-stick intervals
are happening in the 1.9% of plants which use electric head-to-back
stunning. Taking this into account, abattoirs have stun-to-knifing
times of between 0 and at least 45 seconds.
From the MHS graph, we can estimate that
- 13 abattoirs have a stun-to-knife time of 25 seconds
- 18 abattoirs have a stun-to-knife time of 30 seconds
- 5 abattoirs have a stun-to-knife time of 35 seconds
- 5 abattoirs have a stun-to-knife time of 40 seconds
In total, 53 abattoirs have stun-to-knife times of longer
than 19 seconds. This equates to approximately 15% of all
abattoirs slaughtering pigs. Around 39 of these abattoirs
(11% of all pig abattoirs) will be using an electric head-only
A stun-to-knife interval of no more than 15 seconds would
account for the fact that not all animals will remain unconscious
for the average of 42 seconds. 129 abattoirs have stun-to-knife
times of longer than 15 seconds. This equates to approximately
36% of all abattoirs slaughtering pigs. Around 95 of these
abattoirs (27% of all pig abattoirs) will be using an electric
How many pigs regain consciousness?
If we take the extremely conservative estimate that in 11%
of abattoirs, pigs regain consciousness because stun-to-knife
intervals exceed 19 seconds and assume that 11% of pigs are
killed in these abattoirs (an underestimate because premises
which use the captive bolt pistol to stun pigs tend to be
low throughput), we can say that at least 11% of pigs are
regaining consciousness before they die from loss of blood.
This equates to at least 1.8 million pigs regaining consciousness
in the UK every year.
The gas chambers
Around 25% of pigs are stunned through the use of CO2 gas.
CO2 stunning has been criticised extensively on welfare grounds
and for this reason it has been banned completely in the Netherlands.
Scientific papers reveal that animals will not lose consciousness
immediately and will be in great distress for 20 - 30 seconds.
Pigs are supposed to be left in the chamber until the gas
Scientists from Bristol University's Department of Food Animal
Science observed that stunning using CO2 gas caused pigs,
"severe respiratory distress" (53). Pigs tried to escape when
lower concentrations (40 to 70%) of CO2 were used. In a later
paper, Raj and his research team say that, "Squealing observed
during gas killing of pigs, in general, is a matter for great
concern... the respiratory sounds that were observed during
the induction of anaesthesia with a high concentration of
carbon dioxide clearly indicated the severity of distress"
Scientists say that using 90% argon in air or 30% CO2 mixed
with 60% argon would be a more humane option. However, they
acknowledge that the 30/60 mix "could be objectionable on
welfare grounds" because of "the mild to moderate respiratory
discomfort induced" (54).
Why don't abattoirs switch to 90% argon in air? Raj and Gregory
point out that argon is an inert gas occurring naturally in
minute quantities and extracted from the atmospheric air which
therefore makes it more expensive than carbon dioxide gas,
which is extracted from distilleries (55). The reluctance
to change technique must be due to the increased cost that
would be incurred.
The Farm Animal Welfare Council point out that stunning using
argon gas takes, around 3 times as long as with a high concentration
of CO2 in air (56). They say, "This could cause some difficulties
with the current high volume throughput in slaughterhouses.
FAWC does not, however, see this as an insurmountable difficulty
for the industry." (56)
The industry will naturally be reluctant to slow down their
throughput rates - they want to be slaughtering the maximum
number of pigs possible per day in order to obtain maximum
FAWC conclude by recommending that the use of CO2 gas be
phased out. They state, "FAWC recommends that the industry
should concentrate on the use of argon to induce anoxia. High
concentrations of CO2 in air should be phased out as systems
using alternative gas mixtures become commercially available."
Animals are supposed to be stunned in order to render them
immediately unconscious. Pigs stunned using CO2 gas will squeal,
hyperventilate and try to escape for up to 30 seconds before
they lose consciousness and eventually die. CO2 gas causes
great distress to pigs and Viva! believes that this stunning
technique should be banned.
Captive bolt - not recommended
Captive bolt stunning is not recommended for pigs but according
to the MHS, this method is used in 20.5% of pig abattoirs.
The Humane Slaughter Association say that pigs are the most
difficult animals to stun with captive-bolt equipment. They
explain, "The target area is very small... In addition, relative
to other species, the brain lies deep in the head with a mass
of sinuses lying between the frontal bone and the brain cavity...
Older sows and boars may also have a ridge of bone running
down the centre of the forehead. This may prevent the bolt
penetrating the brain cavity and the pig will not be stunned
effectively. Because of the problems which might arise with
adult pigs it is recommended that, where possible, they are
stunned electrically, or destroyed by use of a free-bullet
humane killer or a shotgun." (24)
In light of the obvious problems associated with stunning
pigs with the captive bolt pistol, Viva! questions why this
technique is still permitted.