The slaughter of animals used for food

The slaughter of animals used for food

Making animal products means killing nonhuman animals. This is pretty obvious in the case of meat, leather, fur, and other products that are made from the flesh of animals. But animals are also killed when they are exploited for other purposes such as the production of dairy products and eggs. Younger cows and chickens produce more milk and eggs, and dairy cows and egg-laying hens are killed when exploiting them is less profitable than breeding new animals and exploiting them instead.

A small percentage of animals raised for food are raised on small farms rather than factory farms. Defenders of small farms claim that the animals on them are treated better than those on factory farms. However, no matter what conditions they are raised in, farmed animals are all eventually sent to a slaughterhouse to be killed.

Death is a harm to animals because, as beings with the capacity for positive experiences, they have an interest in living. In slaughterhouses, animals also experience fear and pain before they die. Some of the torments they undergo are described below, starting with aquatic animals, who make up the majority of farmed animals.

Fish farms

While it is virtually impossible to capture sentient aquatic animals in the wild without causing them to suffer, we might think things are different for farmed fishes. But they are not much different. The amount and types of suffering that fishes and other aquatic sentient animals endure during their slaughter, and also prior to it,1 varies from one method to another. But all methods cause significant pain and distress and they all end in death. The methods that are employed to kill fishes include the following:2

1. Asphyxia. Fishes are taken out of water and slowly suffocate because they can only get oxygen from water through their gills. It can take up to 15 minutes for them to die.3

2. Chilling. Fishes are submerged in ice or in almost frozen water, causing hypothermia and death. This method does not necessarily reduce sensitivity to pain, as indicated by the fact that the reduction in temperature has been related to an increase in the animals’ levels of cortisone.4

3. Carbon dioxide narcosis. Fishes are put in tanks in which the water has high levels of carbon dioxide. Carbon dioxide dissolved in high concentrations in water has a narcotic effect on fishes breathing it. This stuns the fishes, but the process is slow, and as the carbon dioxide begins to affect them, they move around violently and try to escape. They display what in the scientific literature is called “aversive behavior”,5 which is a strong indicator of their being distressed.

4. Bleeding without stunning. Fishes are taken out of the water and, while held manually, their gills or their hearts are cut with a knife so they bleed to death. This process can last between four and 15 minutes or more, during which time the fishes are conscious and struggling, just as other animals would in their situation.6

Sometimes an attempt is made to stun fishes before killing them. There are several stunning methods used.

Percussive stunning. The animals are hit with a wooden or plastic club so they lose consciousness.

Electrical stunning. This method is used with big fishes. Fishes are stabbed with a harpoon that has an electrical connection. In some cases, this doesn’t work and the fishes remain conscious while bleeding to death.7

In other cases fishes are killed in a way that, at least in theory, cause them less suffering, such as shooting them in their heads.


Things aren’t very different in land slaughterhouses in which mammals and birds are killed. Mammals and birds also experience fear and pain, as well as being deprived of their lives. In many countries animals are supposed to be stunned first so they don’t suffer, or at least suffer less, when they are killed.

Animals in slaughterhouses also undergo terrible psychological suffering. In addition to the distress of not knowing where they are, they see other animals being killed, and they hear their cries. All this is terribly frightening to them.8 This happens after a very harsh journey from farms.

Transport to killing units

During their trip to the slaughterhouse, animals are crowded together and often have little protection from temperature extremes. They are usually not fed along the way because it’s not in a farmer’s economic interest to give them food when there won’t be time for it to be digested and converted into more flesh,9 and also because it is easier for the truck driver and the slaughterhouse workers if they don’t have to deal with animal waste.

The animals generally arrive at slaughterhouses in a weakened physical and psychological state. They are hungry, exhausted, and often confused and frightened. When they get to the slaughterhouse, there are other factors that can add to their distress and pain such as slippery floors. If an animals falls, others behind them may be injured as well.

Sometimes animals at a slaughterhouse are washed before they are killed. This is often done by pressure washers, which can cause them pain, often in sensitive parts. The temperature of the water can also hurt the animals, and they may find the process very stressful.

In addition, animals are often offloaded from trucks and violently forced to move to and from holding pens on the way to their slaughter. When the animals are so scared that they won’t move without painful prodding, pricks, sticks or electric goads are used, causing pain to the animals. Sometimes hooks are used. One slaughterhouse worker reported:

“Hogs get stressed out pretty easy. If you prod them too much, they have heart attacks. If you get a hog in the chute that’s had the shit prodded out of him and has a heart attack or refuses to move, you take a meat hook and hook it into his bunghole. You try to do this by clipping the hipbone. Then you drag him backwards. You’re dragging these hogs alive, and a lot of times the meat hook rips out of the bunghole. I’ve seen hams — thighs — completely ripped open. I’ve also seen intestines come out. If the hog collapses near the front of the chute, you shove the meat hook into his cheek and drag him forward.”10

In some cases, the animals can get stuck in one part of the slaughterhouse, and then any form of violence at all may be used to move them. A testimony by another slaughterhouse employee shows this very clearly:

“I’ve drug cows till their bones start breaking, while they were still alive. Bringing them around the corner and they get stuck up in the doorway, just pull them till their hide be ripped, till the blood just drip on the steel and concrete. Breaking their legs… And the cow be crying with its tongue stuck out. They pull him till his neck just pop.”11


In the slaughter units, animals are supposed to be stunned before they are killed. Some animals (such as pigs and sheeps) are often stunned without being immobilized first. The workers simply walk up to the animals and stun (or try to stun) them using methods such as electric goads. They do this repeatedly to different animals in the same group.

This method doesn’t work with large animals such as cows because the goad can’t be positioned above them to stun them. To make the stunning process easier and to protect the workers from possible injuries caused by the animals when they try to escape, larger animals are immobilized before they are stunned and killed. The following methods of immobilization are used.

Traditional stunning boxes. These are enclosed spaces where an animal is placed in order to be stunned. The box is narrow so that the animal cannot turn around, and the floor of the box is rough to prevent slipping or falling.12 The person doing the stunning normally stand to the side of the box to shoot the animal. On occasion, the workers fail in the shooting and the animal remains conscious during the hoisting and bleeding.

Boxes with a mechanism for restraining the head. These are boxes that have a restraint mechanism which is closed around the neck of the animals, thus restraining their heads. This type of box is mandatory in certain countries whenever animals are stunned using non-penetrative methods, since they require greater precision when shooting in order to be effective.

Moving rails. These are automatic rails which lead the animal to the stunning area. They are designed in a W shape so that the animals’ legs are separated at all times, ensuring that they cannot turn back.

The method used to keep birds immobilized while they are stunned is different. They are hoisted upside down on a conveyor belt that brings the animals to stunning tanks, which are described below. The birds are often injured and have their legs or other parts of their bodies broken when they are quickly and sometimes violently grabbed and hung from the belt. A former slaughterhouse employee who later repented and became an animal activist, Virgil Butler, described the situation as follows:

“The line is running. The smell is atrocious and the chickens are panicking. Many of them are squawking loudly, some are just sitting there trembling. Sometimes you catch one looking up at you, eye to eye, and you know it’s terrified.”13


Once an animal is sufficiently immobilized (or sometimes, with smaller animals, without immobilizing them), an attempt is made to stun them so they are not conscious when they are killed. This can be done by different methods.


This method gives an electric shock to the animals until they are unconscious. Its method of application is different depending on the type of animal.


Electronarcosis is the most commonly used method on birds (such as chickens, hens, turkeys, geese, and ducks). The most common implementation is to submerge the animals’ heads in a tub with electrified water.14 A current of 80 milliamps is applied for 3 seconds. This process is usually mechanized, with animals hoisted on hooks and dragged through a large tub of electrified water for a few seconds before they get to the next stage in the assembly line where their throats are slit.

Studies have shown that this is very painful for the animals. The current runs through the entire body, usually causing a break in the coracoid and the scapula (shoulder blade), muscular contractions, and hemorrhages.15

In one study, approximately 44% of the chickens submerged in electrified water suffered the breaking of bones and 35% of them had hemorrhages. Also, half of the animals stunned through this system showed ventricular fibrillation. Similar results were obtained in studies carried out in the European Union comparing this method with the gassing method.16 The effectiveness of this method has been doubted as there were reports of animals arriving conscious to the scalding tank.


In the case of pigs, there are two methods of electronarcosis: passing electric current through the brain, or passing electric current through the brain and heart.

1. Passing electric current through the brain. An electric current is applied directly to the head of the animal with the aim of producing an epileptic attack. The current is induced through tongs composed of two electrodes placed on either side of the head under the ears. The tongs have a sharpened piece that pierces the animal’s skin to hold them in place. Another variant consists of applying one electrode under the jaw and another to the side of the neck (behind the ears). When it works, this method will stun the animals for only about 15 seconds, and the animals may regain consciousness before being bled to death, thus suffering not only pain, but also panic and distress.

2. Passing electric current through the brain and hear. This causes a heart attack. This stunning method usually causes death directly by electrocution. One electrode is placed on the forehead or on the groove behind the ear, and another on the back or side of the body, so that the electric current also reaches the heart.

These methods require shaving and dampening the area where the electrodes will be placed to allow for the flow of the current. Not dampening the area, mispositioning the electrodes, applying this type of stunning to an imprecise point of the body, or at different amperage than indicated can cause paralysis of the animal without causing loss of consciousness (which is known as Lost Shock or “nightmare state of Leduc”). This means that the animal will remain awake during the whole process and will suffer the consequent stress and pain. Additionally, if the distance between the electrodes is very short, cardiac arrest does not occur.

The most common discharge equipment is one of low voltage (70-150V), applied for several seconds, during which time the animal sometimes suffers from a painful discharge before becoming stunned. In many cases the discharge is not applied according to the directions, which can cause the animal to suffer a generalized and painful paralysis (if the discharge is lower), or to suffer bone fractures, ecchymosis, and hemorrhages (if the discharge is higher), often without being stunned. But even when they are stunned by the procedure, the animals can suffer pain and fear before losing consciousness.17


Electronarcosis is a seldom used method on cows due to their large size. When it is used on cows, electrical stunning is supposed to be carried out in two rounds. A minimum of 1.5 amps is applied first to the head, followed by another discharge to the body, which should cause cardiac arrest.18

The application of electrodes to a cow may not stun her.19 Depending on the immobilization method used, it may be difficult to keep the electrode secured to the cow’s head when she falls to the ground, which will cause her to feel the shock. Also, incorrect positioning of the electrodes can cause fractures in the spine and hemorrhages, among other problems.


This type of stunning is used in many countries. Animals are led into a chamber that is filled with asphyxiating gas: argon, nitrogen, carbon dioxide, or a combination of these. This makes the animals lose consciousness.

There is a great variation in the response of the animals subjected to gas, which depends, basically, on genetic factors. The loss of consciousness is never instantaneous, but takes from 30-39 seconds.20 The gas can cause very violent reactions and desperate attempts to flee,21 which shows that this method can be very painful and stressful.

Mechanical stunning

There are two kinds of mechanical stunning:


This is with a captive bolt pistol. It shoots a retractable projectile by means of an explosive cartridge or compressed air. The projectile impacts the cerebral cortex and then returns to its original position without becoming lodged in the brain. It causes permanent brain damage.

There is a model of pistol that also propels a stream of water into the open hole, causing further damage to the brain.22 Another practice consists of putting a spoke into the hole created by the projectile to produce lacerations on the brain.


A device with one end shaped like a mushroom is used to hit the cranium without entering into contact with the brain. The stunning is caused by the resulting concussion.23

Mallet or hammer blows

This is used in places with fewer economic resources as it is cheap and simple, although it requires a lot of skill to hit the exact point and leave the animal unconscious. In fact, the success of this method in stunning the animal is only about 50%.24 Frequently it is necessary to administer several blows, which causes terror, stress, and pain to the animals. On many occasions, due to a lack of precision, the animals have their throats slit and slowly bleed to death while fully conscious.

Home-made electrical stunning

This is employed in impoverished countries. It consists of using tongs or cables connected to a house’s current. It is not clear that this method really stun its victims; it certainly does not in the case of bovines and other big animals who are not stunned by low currents.25 It causes a lot of suffering to the animals, in addition to what they will suffer while being killed.

Immobilization without stunning

Severing the spinal cord with a knife. This is the use of a sharpened knife to sever the spinal cord at the base of the skull. It causes immediate immobilization in the animals who suffers it, but it does not cause loss of consciousness, hence the animals remain conscious until they bleed to death.

Killing animals

In places where regulations require it, animals go through a stunning process, usually one of the methods described above, which is intended to render them unconscious or immobile before they are killed. Because the purpose of slaughterhouses is to kill animals as quickly as possible, many are still conscious when their bodies are dragged through scalding tanks and as their throats are slit and their bodies are dismembered.


Once they have gone through the stunning stage, during which they may or may not have been stunned, cows, steers, calves and bulls have their hind legs chained and they are raised so they are hanging upside down. Then a deep knife slits their throats, which severs the carotid artery, and they bleed to death. At the next stage, their heads and feet are cut off, their digestive tracts are taken out, they are skinned and the remaining viscera are extracted from the animals’ carcasses.

In many cases, the animals can be fully conscious when they are killed. Sometimes they do not die in the killing stage and are still fully conscious at the next stage, when they are skinned and cut into pieces. This happens because it takes several minutes to bleed to death. However, the animals are cut into pieces immediately after their throats are slit, so they are very often dismembered alive. As reported in an interview with a slaughterhouse worker:

“From the sticker to the legger is maybe ten seconds. They’re breathing real hard over there, mooing, they’re falling off the rail because they’re alive.”26

Another slaughterhouse employee, Ramón Moreno, whose job was quartering the animals (cutting their bodies into pieces), reported doing this many times every day while they were fully conscious. They were supposed to be dead before they got to Moreno. But too often they weren’t:

“They blink. They make noises,” he said softly. “The head moves, the eyes are wide and looking around.”

Still Moreno would cut. On bad days, he says, dozens of animals reached his station clearly alive and conscious. Some would survive as far as the tail cutter, the belly ripper, the hide puller. “They die,” said Moreno, “piece by piece.”27

“If you put a knife into the cow, it’s going to make a noise: It says, ‘Moo!’.”28

A U.S. Department of Agriculture technician, Tim Walker, reported:

“I complained to everyone — I said, ‘Look at it, they’re skinning live cows in there,’ Walker said. Always it was the same answer: ‘We know it’s true. But there’s nothing we can do about it’.”29

This has been confirmed by other slaughterhouse workers:

“I’ve seen thousands and thousands of cows go through the slaughter process alive,” IBP veteran Fuentes, the worker who was injured while working on live cows, said in an affidavit. “The cows can get seven minutes down the line and still be alive. I’ve been in the side-puller where they’re still alive. All the hide is stripped out down the neck there.”30


Carbon dioxide can be used not only to stun pigs, but also to kill them directly by depriving their bodies of oxygen, so they suffocate to death. However, normally they are only stunned with carbon dioxide and then have their throats slit. Once the pigs go through the stunning stage and whether they are stunned or not, they are hoisted and hung from their hind legs on a conveyor belt that brings them to the place where the workers who kill them are. The workers slit the animals’ throats. Most of the pigs bleed to death. But some do not. Stunning methods are often designed in general for a single species, but they can affect animals within that species differently, due to factors such as their weight. In other cases, the animals are simply not stunned because the process is done very quickly, or because of the way the systems are designed or human error. In these cases, animals are fully conscious when they reach the next step in the slaughterhouse process, which is scalding tanks, baths with very hot water in which animals are literally scalded so that their feathers and hairs can be easily removed.31 Again, there are reports of this by workers:

“I’ve seen hogs in the scalding tub trying to swim.”32

“These hogs get up to the scalding tank, hit the water and start screaming and kicking. Sometimes they thrash so much they kick water out of the tank… Sooner or later they drown. There’s a rotating arm that pushes them under, no chance for them to get out. I’m not sure if they burn to death before they drown, but it takes them a couple of minutes to stop thrashing.”33


In the first stage in a chicken slaughterhouse, chickens are hung upside down on a conveyor belt, and then their heads pass through electrified stunning tanks, which are baths with electrical currents running through them to stun the animals. Next, an automatic blade slits their throats. From there, the conveyor belt pulls them through scalding tanks with boiling water where their feathers are removed.

Hanging from a conveyor belt is very uncomfortable and distressing, and the birds are struggling, flapping their wings and moving their heads. For this reason, when they pass over the electrified tanks, their heads may be raised and they may not be stunned. They may still be moving when they reach the automatic blade. As a result, the blade might not cut their throats. The blade might not touch the animals at all, or instead cut another part of their body, such as the wings, face, or beak.

The slaughterhouse workers might then decapitate the animals that they see have not been killed automatically. However, the conveyor belt runs quickly and cannot stop, so they often miss animals. This means the animals will reach the scalding tanks fully conscious, where they will be boiled alive.

Additional factors that make the torment worse

There are additional factors that can cause slaughterhouse deaths to be even more painful and stressful, such as improperly working equipment. A slaughterhouse worker says:

“The line is so fast there is no time to sharpen the knife. The knife gets dull and you have to cut harder.”34

Others factors include the lack of concern workers may have for the animals. In order to be able to kill the animals, slaughterhouse workers need to be almost completely insensitive to them. As one worker put it:

“Pigs down on the kill floor have come up and nuzzled me like a puppy. Two minutes later I had to kill them – beat them to death with a pipe. I can’t care.”35

Moreover, animals can be the victims of some workers’ brutality. There are many records of cases of terrible pain being inflicted on animals on purpose. This can happen if workers are stressed, are having a bad day, or if some animals struggles for their life and the worker wants to retaliate. In any of those situations, as on farms, the animals are completely defenseless and the workers are often in a situation in which they can do whatever they want to the animals. The following statement by another slaughterhouse worker shows this quite clearly:

“You’re already going to kill the hog, but that’s not enough. It has to suffer… you don’t just kill it, you go in hard, push hard, blow the windpipe, make it drown in its own blood. Split its nose. A live hog would be running around the pit. It would just be looking up at me and I’d be sticking, and I would just take my knife and—eerk—cut its eye out while it was just sitting there. And this hog would just scream. One time I took my knife – it’s sharp enough – and I sliced off the end of a hog’s nose, just like a piece of bologna. The hog went crazy for a few seconds. Then it just sat there looking kind of stupid. So I took a handful of salt brine and ground it into his nose. Now that hog really went nuts, pushing its nose all over the place. I still had a bunch of salt in my hand – I was wearing a rubber glove – and I stuck the salt right up the hog’s ass. The poor hog didn’t know whether to shit or go blind… But I wasn’t the only guy doing this kind of stuff… One guy I work with actually chases hogs into the scalding tank.”36

There is no reliable way to control this, even with frequent inspections. Someone who harms animals this way can stop doing it when he’s being watched. As long as people demand animal products, there will be industrial animal agriculture and this will continue to happen.

Even when there is no unusual abuse, the standard slaughterhouse practices we have seen above can cause animals to suffer terribly. And in all cases, even if they don’t suffer much pain or distress, nonhuman animals are harmed by being deprived of their lives.

Further readings

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Anil, M. H.; McKinstry, J. L.; Wotton, S. B. & Gregory, N. G. (1995) “Welfare of Calves – 1. Investigations into some aspects of calf slaughter”, Meat Science, 41, pp. 101-112.

Blackmore, D. K. (1984) “Differences in behaviour between sheep and cattle during slaughter”, Research in Veterinary Science, 37, pp. 223-226.

Chandroo, K. P.; Yue, S. & Moccia, R. D. (2004) “An evaluation of current perspectives on consciousness and pain in fishes”, Fish and Fisheries, 5, pp. 281-295.

Croft, P. S. (1952) “Problems with electrical stunning”, Veterinary Record, 64, pp. 255-258.

Dalmau, A.; Nande, A.; Vieira-Pinto, M.; Zamprogna, S.; Di Martino, G.; Ribas, J. C. R.; Paranhos da Costa, M.; Halinen-Elemo, K. & Velarde, A. (2016) “Application of the welfare quality® protocol in pig slaughterhouses of five countries”, Livestock Science 193, pp. 78-87.

Daly, C. C.; Gregory, N. G. & Wotton, S. B. (1987) “Captive bolt stunning of cattle-effects on brain function and the role of bolt velocity”, British Veterinary Journal, 143, pp. 574-580.

Eikelenboom, G. (1982) Stunning animals for slaughter, London: Martinus Nijhoff.

European Commission. Scientific Veterinary Committee, Animal Welfare Section (1996) Report on the slaughter and killing of animals, Brussels: Commission of the European Communities [accessed on 14 February 2012].

Ewbank, R.; Parker, M. J. & Mason, C. W. (1992) “Reactions of cattle to head restraint at stunning: A practical dilemma”, Animal Welfare, 1, pp. 55-63.

Fossat, P.; Bacqué-Cazenave, J.; de Deuerwaerdère, P.; Delbecque, J.-P. & Cattaert, D. (2014) “Anxiety-like behavior in crayfish is controlled by serotonin”, Science, 344, pp. 1293-1297.

Gentle, M. J. & Tilston, V. L. (2000) “Nociceptors in the legs of poultry: Implications for potential pain in pre-slaughter shackling”, Animal Welfare, 9, pp. 227-236.

Grandin, T. (1998a) “The feasibility of using vocalization scoring as an indicator of poor welfare during slaughter”, Applied Animal Behaviour Science, 56, pp. 121-128.

Grandin, T. (2002) “Return to sensibility problems after penetrating captive bolt stunning of cattle in commercial beef slaughter plants”, Journal of the American Veterinary Medical Association, 221, pp. 1258-1261.

Gregory, N. G. (1985) “Stunning and slaughter of pigs”, Pig News and Information, 6, pp. 407-413.

Gregory, N. G. (1988) “Turkey stunning”, Turkeys, 36 (3), pp. 29-30.

Gregory, N. G. (1996) “Welfare of poultry at slaughter”, in Bremner, A. S. & Johnston, A. M. (eds.) Poultry meat hygiene and inspection, London: W. B. Saunders, pp. 53-72.

Gregory, N. G. & Wotton, S. B. (1984a) “Sheep slaughtering procedures. 11. Time to loss of brain responsiveness after exsanguination or cardiac arrest”, British Veterinary Journal, 140, pp. 354-360.

Gregory, N. G. & Wotton, S. B. (1984b) “Time of loss of brain responsiveness following exsanguination in calves”, Resource Veterinary Science, 37, pp. 141-143.

Gregory, N. G. & Wotton S. B. (1986a) “Pig slaughtering procedures: Time to loss of brain”, Research in Veterinary Science, 40, pp. 148-151.

Gregory, N. G. & Wotton, S. B. (1986b) “Effect of slaughter on the spontaneous and evoked activity of the brain”, British Poultry Science, 27, pp. 195-205.

Gregory, N. G. & Wotton, S. B. (1988) “Stunning of chickens”, Veterinary Record, 122, p. 399.

Gregory, N. G. & Wotton S. B. (1990) “Comparison of neck dislocation and percussion of the head on visual evoked responses in the chicken’s brain”, Veterinary Record, 126, pp. 570-572.

Hoenderken, R. (1978) Elektrische bedwelming van slachtvarkens, Doctoral thesis, Universiteit Utrecht.

Hoenderken, R. (1983) “Electrical and carbon dioxide stunning of pigs for slaughter”, in Eikelenboom, G. (ed.) Stunning of animals for slaughter, Boston: Martinus Nijhoff, pp. 59-63.

Huntingford, F. A.; Adams, C.; Braithwaite, V. A.; Kadri, S.; Pottinger, T. G.; Sandøe, P. & Turnbull, J. F. (2006) “Current issues in fish welfare”, Journal of Fish Biology, 68, pp. 332-372.

Iwama, G. W.; Pickering, A. D.; Sumpter, J. P. & Schreck, C. B. (eds.) (2012 [1997]) Fish stress and health in aquaculture, reissue ed., Cambridge: Cambridge University Press.

Jarvis, A. M.& Cockram, M. S. (1995) “Some factors affecting resting behaviour of sheep in slaughterhouse lairages after transport from farms”, Animal Welfare, 4, pp. 53-60.

Kestin, S. C.; Vis, J. W. van de & Robb, D. H. F. (2002) “Protocol for assessing brain function in fish and the effectiveness of methods used to stun and kill them”, Veterinary Record, 150, pp. 302-307.

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Pearson, A. J.; Kilgour, R.; Delangen, H. & Payne, E. (1977) “Hormonal responses of lambs to trucking, handling and electric stunning”, New Zealand Society Animal Production, 37, pp. 243-249.

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Raj, A. B. M. & Gregory, N. G. (1996) “Welfare implications of the gas stunning of pigs: 2. Stress of induction of anaesthesia”, Animal Welfare, 5, pp. 71-78.

Raj, A. B. M.; Johnson, S. P.; Wotton, S. B. & McKinstry, J. L. (1997) “Welfare implications of gas stunning pigs: 3. The time to loss of somatosensory evoked potentials and spontaneous electrocorticogram of pigs during exposure to gases”, Veterinary Journal, 153, pp. 329-340.

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2 Robb, D. H. F. & Kestin, S. C. (2002) “Methods used to kill fish: Field observations and literature reviewed”, Animal Welfare, 11, pp. 269-282. Robb, D. H. F.; Wotton, S. B.; McKinstry, J. L.; Sørensen, N.K. & Kestin, S. C. (2000) “Commercial slaughter methods used on Atlantic salmon: Determination of the onset of brain failure by electroencephalography”, Veterinary Record, 147, pp. 298-303.

3 Benson, T. (2004) Advancing aquaculture: Fish welfare at slaughter, London: Winston Churchill Memorial Trust, p. 23.

4 Lambooij, E.; Vis, J. W. van de; Kloosterboer, R. J. & Pieterse, C. (2002) “Welfare aspects of live chilling and freezing of farmed eel (Anguilla anguilla L.): Neurological and behavioural assessment”, Aquaculture, 210, pp. 159-169; Skjervold, P. O., Fjaera, S. O., Ostby, P. B. & Einen, O. (2001) “Live-chilling and crowding stress before slaughter of Atlantic salmon (Salmo salar)”, Aquaculture, 192, pp. 265-280. Yue, S. [ca. 2009] An HSUS report: The welfare of farmed fish at slaughter, Washington, D. C.: Humane Society of the United States, p. 4 [accessed on 27 November 2014].

5 Salmons stunned in this way may fight violently for several minutes, see Robb, D. H. F.; Wotton, S. B.; McKinstry, J. L.; Sørensen, N. K. & Kestin, S. C. (2000) “Commercial slaughter methods used on Atlantic salmon: Determination of the onset of brain failure by electroencephalography”, op. cit.

6 Benson, T. (2004) Advancing aquaculture: Fish welfare at slaughter, op. cit., p. 6.

7 Ibid., p. 9.

8 The author who has worked most extensively on this is Temple Grandin, who has collaborated with the animal exploitation industry to support the exploitation of animals while reforming it so animals suffer less. She is in favor of killing animals for food, so her work does not address the harm to animals of having their lives taken away. See for instance: Grandin, T. (1987) “Animal handling”, Veterinary Clinics North America: Food Animal Practice, 3, pp. 323-324; (1988b) “Double rail restrainer conveyor for livestock handling”, Journal of Agricultural Engineering Research, 41, pp. 327-338; (1998c) “Solving livestock handling problems in slaughter plans”, in Gregory, N. G. & Grandin, T. Animal welfare and meat science, Wallingford: CABI Publishing, pp. 42-63; (1990) “Design of loading and holding pens”, Applied Animal Behavior Science, 28, pp. 187-201; (1991) Recommended animal handling guidelines for meat packer, Washington, D. C.: American Meat Institute; (1992) “Observation of cattle restraint devices for stunning and slaughtering”, Animal Welfare, 1, pp. 85-90; (1994) “Euthanasia and slaughter of livestock”, Journal of American Veterinary Medical Association, 204, pp. 1354-1360; (1996) “Factors which impede animal movement in slaughter plans”, Journal of American Veterinary Medical Association, 209, pp. 757-759; (1997a) “Assessment of stress during handling and transport”, Journal of Animal Science, 75, pp. 249-257; (1997b) “Good management practices for animal handling and stunning”, Washington, D. C.: American Meat Institute; (1997c) Survey of stunning and handling in federally inspected beef, veal, pork and sheep slaughter plants, Fort Collins: Grandin Livestock Handling Systems.

9 Kirton, A. H.; Moss, R. A. & Taylor, A. G. (1971) “Weight losses from milk and weaned lamb in mid Canterbury resulting from different lengths of starvation before slaughter”, New Zealand Journal of Agricultural Research, 14, pp. 149-160 [accessed on 15 January 2014]. Terlouw, E. M. C.; Arnould, C.; Auperin, B.; Berri, C.; Le Bihan-Duval, E.; Deiss, V.; Lefèvre, F.; Lensink, B. J. & Mounier, L. (2008) “Pre-slaughter conditions, animal stress and welfare: Current status and possible future research”, Animal, 2, pp 1501-1517.

10 Eisnitz, G. (1997) Slaughterhouse: The shocking story of greed, neglect, and inhumane treatment inside the U.S. meat industry, Amherst: Prometheus, p. 82.

11 Ibid., p. 145.

12 Grandin, T. (1991) Recommended animal handling guidelines for meat packer, op. cit.

13 Butler, V. (2003) “A night in Tyson’s hell”, The Cyberactivist, September 23 [accessed on 12 March 2013].

14 Bilgili, S. F. (1992) “Electrical stunning of broilers – Basic concepts and carcass quality implications: A review”, The Journal of Applied Poultry Research, 1, pp. 135-146.

15 Hillebrand, S. J. W.; Lambooij, E. & Veerkamp, C. H. (1996) “The effect of alternative electrical and mechanic stunning methods on haemorrhaging and meat quality of broiler breast and thigh muscles”, Poultry Science, 75, pp. 664-671.

16 Göksoy, O.; McKinstry, L. J.; Wilkins, L. J.; Parkmanm I.; Phillips, A.; Richardson, R. I. & Anil, M. H. (1999) “Broiler stunning and meat quality”, Poultry Science, 78, pp. 1796-1800. Raj, A. B.; Gregory, N. G.; Wilkins, L. J. (1992) “Survival rate and carcass downgrading after the stunning with carbon dioxide-argon mixtures”, Veterinary Record, 130, pp. 325-328.

17 Adams, D. B. & Sheridan, A. D. (2008) Specifying the risks to animal welfare associated with livestock slaughter without induced insensibility, Canberra: Australian Government Department of Agriculture, pp. 1-55.

18 Gregory, N. G. (1993) “Slaughter technology electrical stunning in large cattle”, Meat Focus, pp. 32-36; (1994) “Preslaughter handling, stunning and slaughter”, Meat Science, 36, pp. 45-56.

19 Atkinson, S.; Velarde, A. & Algers, B. (2013) “An assessment of carbon dioxide stunning in pigs”, Animal Welfare, 22, pp. 473-481.

20 Gregory, N. G.; Moss, B. & Leeson, R. (1987) “An assessment of carbon dioxide stunning in pigs”, Veterinary Record, 121, pp. 517-518.

21 Dodman, N. H. (1977) “Observations on the use of the Wernberg dip-lift carbon dioxide apparatus for preslaughter anesthesia of pigs”, British Veterinary Journal, 133, pp. 71-80. Grandin, T. (1988d) “Possible genetic effect in pig’s reaction to CO2 stunning”, Congress proceedings: 34th International Congress of Meat Science and Technologies, 29 August – 2 September, Brisbane, Australia, pp. 96-97.

22 Bauer, N. A.; Buckley, S. A. & Ferris, R. A. (1997) “Brain emboli in the pulmonary arteries, hepatic veins and renal veins of slaughtered cattle as a sequelae to the stunning process”, Epidemiology and Economics Symposium ’97, August 19-21, Fort Collins, Colorado.

23 Ramantanis, S. B.; Hadžiosmanović, M. & Stubičan, D. (2005) “Preventive measure against possible BSE-hazard: Irreversible electrical cattle stunning – a review”, Veterinarski Arhiv, 75, pp. 83-100 [accessed on 9 September 2012].

24 Lambooij, E.; Spanjaard, W.; Eikelenboom, G. (1981) “Concussion stunning of veal calves”, Fleischwirtchaft, 61, pp. 98-100.

25 Wotton, S. B.; Gregory, N. G.; Whittington, P. E. & Parkman, I. D. (2000) “Electrical stunning of cattle”, Veterinary Record, 147, pp. 681-684.

26 Eisnitz, G. (1997) Slaughterhouse: The shocking story of greed, neglect, and inhumane treatment inside the U.S. meat industry, op. cit., p. 216.

27 Warrick, J. (2001) “They die piece by piece”, Washington Post, 10 April, p. A01.

28 Ibid.

29 Ibid.

30 Ibid.

31 Ibid.

32 Eisnitz, G. (1997) Slaughterhouse: The shocking story of greed, neglect, and inhumane treatment inside the U.S. meat industry, op. cit., p. 33.

33 Ibid., p. 84.

34 Human Rights Watch (2005) “Blood, sweat and fear: Workers’ rights in U.S. meat and poultry plants”, Human Rights Watch, January [accessed on 8 March 2013]. Concern here is only for the slaughterhouse workers’ safety, as it is typical of human rights organizations that are not concerned in the least for animals. Yet we can clearly understand how this harms animals, who will suffer significantly due to the poor equipment with which they are killed.

35 Eisnitz, G. (1997) Slaughterhouse: The shocking story of greed, neglect, and inhumane treatment inside the U.S. meat industry, op. cit., p. 87.

36 Ibid., pp. 92-93.