Captive bolt rarely used for sheep
According to the MHS animal welfare survey 1997/8, "Captive bolt stunning [sheep and pigs] is used in a high proportion of slaughterhouses, however, these were mainly low throughput premises and represent a very small percentage of the national kill." (10)
Repeat Stuns and Mis-stuns
According to the MHS, the majority of sheep in British abattoirs are stunned using the head-only electrical method. The MHS say that the average current applied during the electrical stunning of sheep is 1.2 amps (10). However, this is an average figure covering both head-only and head-to-back electrical stunning. Individual averages for each stunning system are not published.
Stunning animals who are unrestrained in a pen with electric tongs is not a straightforward procedure. In a busy, crowded slaughterhouse environment where staff are untrained, sheep routinely escape the grasp of the stunning tongs. The brief application of the tongs will give them a painful electric shock rather than a stun.
A scientific paper published in the British Veterinary Journal in 1984 observed stunning in over 9,000 sheep being killed at 40 abattoirs. They found that in the abattoirs using electrical stunning there were 467 interrupted stunnings which, "often occurred immediately after the first application of the stunning tongs; the sheep fell to the floor slipping out of the grasp of the tongs". (36) Clearly, mis-stuns are a big problem.
The researchers also saw 109 sheep who were electrically stunned on two or more separate occasions. 37 sheep fell from their shackles between the stunning and sticking points and 59% of these were restunned because of it.
Larger abattoirs now operate conveyor belt systems so that animals are restrained as they approach the stun-operator. However, Miriam Parker from the Humane Slaughter Association said to Viva! this year that, "the problems of double-stun or mis-stun can and do occur". (37)
Sheep regain consciousness
Assuming that an electrical stun causes some animals to lose consciousness (see Does an electrical stun actually cause unconsciousness, page 39 and Does electrical stunning cause pain?, page 40), are they unconscious right up until the point of death?
In order to calculate this, we need to look at the period of unconsciousness produced by a stun and compare this to the time duration between stunning and knifing and the length of time it then takes for a sheep to lose brain responsiveness.
How long does the effect of the stun last?
C.J. Cook found that at 1.0 A, stun durations of 2 seconds result in a seizure-like state lasting for 25 seconds in sheep (38). Stun durations as long as 7 seconds still only resulted in a seizure-like state lasting for 32 seconds. (38)
How long is the interval between stunning and knifing?
According to the Meat Hygiene Service 1997/8 Animal Welfare Review, the interval between stunning and knifing recorded in those plants using head only electrical stunning ranged from 3 seconds to as much as 70 seconds (10). A more precise breakdown of the figures is not given. However Gregory and Wotton surveyed stun to knifing intervals for electrically stunned sheep in UK abattoirs in 1984 and found that the average interval was 21 seconds. (36)
How long do sheep take to lose brain responsiveness:
Sheep lose brain responsiveness in an average of 14 seconds if both carotid arteries and the jugular veins are severed (23). Some will take longer but after 27 seconds, 99% of sheep will have lost brain responsiveness if knifed in this way. However, UK law only requires one carotid artery to be cut and in this case, sheep take an average of 70 seconds to lose brain responsiveness.
How long must sheep be left to bleed out for before they can be skinned?
By law, 20 seconds.
Do sheep regain consciousness?
Using these figures, we can calculate whether sheep are regaining consciousness before they die.
Case 1: Both carotid arteries cut
Length of seizure: 30 seconds
Time between stunning and knifing: 21 seconds
Time to loss of brain responsiveness: 14 seconds
The sheep will regain consciousness 5 seconds before she dies. This is an "average" scenario when a sheep is knifed according to "best practice".
Case 2: One carotid artery cut
Length of seizure: 30 seconds
Time between stunning and knifing: 21 seconds
Time to loss of brain responsiveness: 70 seconds
Time before skinning begins: 20 seconds
The sheep will regain consciousness while hanging upside down bleeding to death. She will be conscious for 61 seconds before she dies. Skinning may commence 20 seconds after her throat is cut so she will still be conscious at this stage.
Viva! fears that millions of electrically stunned sheep in British abattoirs are regaining consciousness before they die from loss of blood. Our fears are borne out by our video footage, which shows clearly conscious sheep kicking and struggling as they hang upside down on the shackle line.
Estimated number of sheep regaining consciousness
56% of plants use head-only electric stunning for sheep. These are mainly high throughput premises so to say that they slaughter 56% of sheep killed in the UK each year is conservative. This adds up to 10.4 million sheep a year.
Sheep will only stay unconscious until brain death if the interval between stunning and knifing is less than average i.e. under 21 seconds. Half of the sheep who are stunned electrically may therefore be knifed quickly enough to enable unconsciousness to be maintained. This means that 5 million sheep a year are regaining consciousness before they die.
Does an electrical stun actually cause unconsciousness?
Scientific studies have questioned whether electrical head-only stunning does, in fact, induce a state of unconsciousness. Studies have shown that electrically stunned sheep have periods of responsiveness when they are fully aware of their surroundings and what is happening to them.
Researchers at Bristol University's Department of Food Animal Science examined whether electrically stunned sheep respond to flashing lights following a stun. They found that, "The epileptiform phase is interposed with periods of cortical responsiveness and the possibility cannot be ruled out that these correspond to transient periods of perception... There is as yet no unequivocal scientific evidence which shows how electrical stunning actually stuns an animal." (40)
The scientists produced a follow up paper on electrical stunning in 1988. They electrically stunned sheep and examined whether they then responded to "potentially painful stimuli" - like manual pinching of the ear and electrical stimulation of the tooth. They conclude that electrical stunning does induce a state of analgesia (the animal will not be able to feel pain) but this does not alter their previous observation that electrically stunned animals have periods of consciousness which can last up to 8 seconds (40). Crucially, they explain that, "It was not possible to say whether responsiveness to the potentially painful stimuli was lost instantaneously at electrical stunning". (41) Recent scientific research has demonstrated that because of this, the stun itself will cause extreme pain (see page 40 - Does electrical stunning cause pain?).
The researchers conclude that, "it can be said that there is a period of analgesia following electrical stunning. In legal and ethical terms, this finding raises the question of whether animals should be, 'rendered insensible to pain' or 'rendered insensible' when they are slaughtered for meat consumption."
UK law has taken these findings into account and stunning is now legally defined as, "any process which causes immediate loss of consciousness which lasts until death." But does this mean electrical stunning has suddenly begun to render animals unconscious?
In January 2000, Viva! wrote to researcher Steve Wotton and asked, "Am I right in saying that after being stunned in this way [electric head-only stun] sheep cannot feel pain but that they are not actually unconscious i.e. they are aware of their surroundings?"
Steve Wotton replied, "Your interpretation of our conclusions is generally correct... Our experiment clearly demonstrated the need for a change in the legislative definition... I personally believe that this has added to our understanding of electrical stunning and has 'tightened' the legislation... I am unaware of further research that is specific to this area, since our last publication". (42)
Viva! then asked, "I understand that in response to your research, MAFF have changed legislation so that stunning must cause an instant loss of consciousness rather than an instant insensibility to pain. However, I'd be grateful if you could clarify whether current electrical head-only stunning techniques used on sheep do in fact ensure an instant loss of consciousness - in light of your research. How can this be guaranteed if no further research into this area has been done?"
Wotton replied, "The question that you raise regarding electrical head-only stunning and the induction of immediate unconsciousness in sheep has not been approached in this laboratory recently."
There appears to be no scientific evidence proving that electrical head-only stunning renders animals unconscious.
Does electrical stunning cause pain?
Wotton and Gregory were not able to ascertain whether electrical stunning causes an immediate insensibility to pain. Dr Harold Hillman, Director of the Unity Laboratory of Applied Neurobiology believes that passing an electric current through the brain of a conscious animal is a barbaric procedure which he describes as, "torture". (44) He says, "Of course, one cannot ask an animal if an electric stun is painful but there is plenty of evidence from humans subjected to large electrical currents."
He cites several examples to prove his belief that electric stunning causes pain:
"In China, Iraq, South America and many other countries, electricity is used to torture conscious people. Amnesty International has documented this extensively. Indeed, I have only recently managed to persuade the American judicial authorities that the electric chair is painful.
"If for example you need a wart on your finger cauterised (burnt off), your doctor gives you a local anaesthetic, otherwise the pain would be unbearable.
"It is painful to put one's fingers across the electric mains.
"Electricity causes burns to the skin; burns are extremely painful."
So why is it assumed that electrical stunning is not painful? Says Hillman, "The reasons for which people do not believe that electrical stunning of animals or electrocution of prisoners is painful is that the normal reaction of a conscious animal to pain is to move violently and make loud noises. However, the massive electrical current stimulates all the muscles maximally and this paralyses the animal. Thus they can neither move violently, nor can their vocal chords make noises. Their observers naturally think that they are not in pain." (45)
Millions of animals continue to be stunned electrically despite scientific concerns that animals are not rendered unconscious and will suffer extreme pain when they are stunned.