Vegetarians International Voice for Animals

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 goad).

Food withdrawal

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 and afraid.

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. (48)

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 concerns.

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 stun.

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 head-only stun.

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 kills them.

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" (54).

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 profit.

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.