Posted by: Chris Cole | June 2, 2011

Set phasers to stun? MooooOOOOooo…!!

A story produced by the ABC’s “Four Corners” program, which aired on Monday evening, has caused something of a furore in the community regarding the ethical aspects of Australia’s exporting of live cattle to Indonesia. While many issues were raised, the central theme was the treatment of the animals at the abattoirs to which they were distributed once in Indonesia. Specifically targeted were the methods of restraint and slaughter employed in these abattoirs, and the amount of suffering and, in some cases, wanton abuse, endured by the cattle prior to their death.

Footage of abattoir workers cruelly kicking the cattle, and striking them repeatedly and viciously with blunt objects needs no further discussion. The people involved would benefit from some time tied to a post while someone else does exactly the same thing to them. I suspect this would be most instructive for them, and personally, I would be delighted to volunteer my time to help out.

Similarly, depiction of the methods used to secure the cattle for slaughter leaves no room for any sensible debate. Roping an animal’s legs and “assisting” it to slip over on a wet concrete slope, only to then struggle to keep it still, with a significant delay to actual slaughter, is fairly obviously not the best way to go about the job.

The more moot point* has been the ethical dilemma over which method of slaughter is the more humane: ritual slaughter as prescribed by some religions, or slaughter after stunning. The slaughter of warm furry animals is always going to be an emotive topic, but while a lot of the heated rhetoric prompted by the confronting images broadcast on Four Corners could be reasonably described as spur of the moment emotional backlash, there is a sensible and rational argument to be explored here, and what follows aims to achieve what I hope is a fair overview of what scant evidence there is in this field.

Ritual Slaughter of Animals

Several religions require their followers to adhere to a form of ritual slaughter of their livestock in order for the meat so obtained to be considered acceptable for human consumption. Among the three prevalent monotheistic religions of modern times, Judaism and Islam both still require ritual slaughter of livestock in order to render the meat “kosher” or “halal” respectively. The requirements of the kosher and halal production of meat were intended primarily to ensure the humane treatment of livestock in an era when a very sharp knife wielded very quickly by very skilled hands was without doubt the least torturous way to end an animal’s life. The prescribed requirements also extended to the treatment and upkeep of the animal throughout its life, well before the time of slaughter.

While fine details vary, the religiously prescribed ritual slaughter of livestock essentially mandates that the animal should be alive, well and conscious at the time of slaughter. The animal is then to be killed by way of a long, deep transverse incision through the soft tissues of the neck. This incision should be performed in one smooth motion, and done in such a manner as to ensure that both carotid arteries (which supply most of the blood to the brain) and both jugular veins (which drain most of the blood from the brain) as well as the trachea (windpipe) and usually the oesophagus are all completely severed. This is intended to deprive the brain of its blood supply as quickly as possible, thus rendering the animal unconscious in the shortest possible time.

Specific details can vary due to differences resulting from Jewish and Islamic divergence; one might consider it ironic that they share a common ancestor, and then diverged, evolving into quite distinct species of religion that nonetheless, and as any biologist might expect, retain several traits and characteristics in common. (Interestingly, to extend the biologic analogy further, both “species” quite enthusiastically compete for disputed shared territory, too). There is also some variation between countries and sub-sects of these religions due to subtlely different interpretations of their holy books.

The salient points regarding ritual slaughter are essentially that:

– It is intended to be a quick and humane method of slaughter.
– The animal is conscious at the time of slaughter.
– The animal is killed with a deep cut across the throat severing the blood vessels and trachea.

Ideal practice is for the animal to be contained and upright at the time the incision is made, and for the job to be done with an exceptionally sharp knife in one single, smooth and continuous motion. Unfortunately these conditions are not always met, and certainly they were nowhere to be seen in the abattoirs featured in the Four Corners story this week. The RSPCA scientist reviewing the footage supplied to Four Corners reported that of the 49 animals she had footage of, the average number of cuts made to do the job was 10, and some took up to 33 separate cuts with the knife to properly sever the important neck structures. All of the cattle slaughtered were also lying down on wet concrete with their legs roped and tractioned, rather than upright in a containment pen.

“Modern” / “Humane” Slaughter  …or… Stunning Before Slaughter

The standard of practice in Australia, and all developed nations where law is not dictated by religious dogma, is for livestock to be “stunned” immediately before they are slaughtered. Stunning can mean different things in different countries, and for different livestock species. For cattle, it is almost always the use of something called a captive bolt pistol. This is a pneumatically powered device that drives a blunt, rather heavy piece of metal (the bolt) against the skull of the animal. The bolt cannot leave the device, and has a restricted travel distance (hence “captive bolt”). It is featured as a somewhat novel murder weapon in the movie “No Country For Old Men”. It is not designed to penetrate the skull, and almost never does. Rather, the impact causes percussive injury to the brain (think of the world’s worst concussion from a very solid whack to the head) which is intended to render the animal immediately unconscious, and thus unaware and unable to feel any pain or distress when its throat is sliced open.

There is concern in some quarters regarding two aspects of percussive stunning. Firstly, that bolt stunning causes brain matter to enter the bloodstream (which it absolutely does; the literature is unanimous in this finding and so I have not bothered to include references), which is of concern if you live in an area where Bovine Spongiform Encephalopathy (BSE), otherwise known as mad cow disease, is endemic. Secondly, the possibility that bolt stunning does not actually render the animal insensate to pain and that it is therefore pointless. Advocates of the latter viewpoint with a religious bent go on to suggest that since stunning may not work anyway, then ritual slaughter is just as humane.

So what does science have to say on the subject? Unfortunately, not a whole hell of a lot. There has been very little formal research conducted to answer the question of whether stunning is more humane than non-stunned ritual slaughter. However, while the pickings are slim, let’s proceed with a round-up of the available evidence…

Evidence Quoted as Being In Favour of Ritual Slaughter

A colleague of mine brought an article to my attention, written in 2010 by one Karima Hamdan, entitled “Halal Hysteria”. It is a very eloquently written overview of the media hype surrounding this issue, with some discussion of evidence for and against the effectiveness of captive bolt stunning in cattle, and electrical stunning in both sheep and poultry. The author gets a little carried away at the end, reminding us that these animals are all Allah’s creatures, etc., but the main body of the article is a good summary and well-considered argument for why stunning might not be as humane as we’d like to think it is, and is a worthwhile read [1].

At the risk of raining on someone’s parade, bursting someone else’s bubble, or  otherwise buggering up a third person’s unspecified metaphorical device, it has to be said that the article’s discussion of captive bolt stunning in cattle may have taken a somewhat superficial tour of the available evidence. In the playground of “balance” in media reporting of contentious issues, opposing viewpoints are often represented as equally valid, out of all proportion to the reality of the situation, in order to seem politically correct and inclusive (yes, it’s all very warm and fuzzy), whereas in the real world of science we do our best to portray an accurate view of the evidence, however it falls. In this case, however, it may be fair to say that Karima has intentionally loaded the fat kid onto one end of the seesaw of balance, ignoring the conga line of skinny kids standing in the background.

Karima’s article, and almost every page on the web that involves a link to or quote from the scientific literature on this topic, references a paper published in a German veterinary journal in 1978 by Schulze, et al. [2]. Karima infers from the Schulze paper that:

1. Halal slaughter was not associated with any signs of pain.
2. Stunned animals showed EEG tracings consistent with perception of pain.

Okay. First things first. The 1978 paper by Schulze was a review article offering an overview largely of the political and regulatory environment pertaining to animal processing and slaughter in Germany at the time. The information regarding EEG findings in slaughtered animals was actually sourced from a short report by one of his colleagues, A.S. Hazem,  in 1977, based on research conducted by the Veterinary University of Hanover’s clinic for clawed/hoofed animals. The pertinent subset of data for captive bolt stunning of cattle was the result of studying precisely 15 animals (yes, n = 15), with 5 of them stunned, and 10 of them ritually slaughtered without stunning. The results were as follows:

– In ritually-slaughtered animals (n=10):
– No immediate change in EEG seen when the throat was cut.
– Flatline EEG was seen at <= 23 seconds in 7 of 10 animals. No comment is made on how long it took for the other 3 (presumably longer?).

– In bolt-stunned animals (n=5):
– All 5 animals showed EEG changes consistent with a seizure-like state.
– Flatline EEG was seen at <= 28 seconds in 4 out of 5 animals. Again, with no comment on the 5th animal.
– The author notes, several times, that the EEG changes seen in the stunned animals “…almost certainly eliminates a sense of pain”.

Karima infers that the ritual slaughter was not associated with any signs of pain, based on the fact that the (simplified) EEG trace did not change significantly when the animal’s throat was cut. It is unclear what changes one might expect to see in such an EEG trace due to pain, as such changes are quite subtle (though certainly detectable) even in human subjects with very complex EEG signal processing. It is questionable whether one would expect to see significant changes with the primitive equipment and processing available in 1978. Also, the wording of Schulze’s article is non-specific as to what happened a bit later than “immediately” but before the flatline EEG. Twenty three seconds is a long time when you’re standing around with your throat sliced open. Unfortunately the raw data from Hazem’s 1977 report is not readily available online, so making any more accurate interpretation is regrettably not possible at this time**.

The inference is also made that stunned animals showed EEG tracings consistent with pain, and this interpretation of the results is promulgated on other pro-Halal websites and blog entries [3]. The results reported by Schulze, and his own conclusion in the 1978 paper, simply do not support this assertion. Schulze concludes that:  “After captive bolt stunning most severe general disturbances (waves of 1-2 Hz) occurred in the EEG, which almost with certainty eliminates a sense of pain.” It is likely that a superficial reading of the paper, or a mis-translation from the original German, in which it was published, may be responsible and the error passed on a la Chinese whispers style, without anyone going back to check the paper for themselves. (Tell a lie, repeat the lie, the lie becomes the truth… as they say).

There was no other evidence in the scientific literature supporting the conclusion that ritual slaughter was less painful or more humane than stunning.

Evidence For What Happens To Stunned and Non-Stunned Cattle

Time to Physical Collapse

One good study published in 2010 addresses this question. Gregory et al. [4] had a look at what happened to cattle (n = 174) in a British abattoir that were ritually slaughtered without stunning. Note that this is in a modern facility where the cattle were kept upright in a containment device, subject to a single halal-compliant cut with a very sharp knife, and then released to stand or collapse as they pleased. The results were as follows:

– 14% of the animals collapsed, stood back up, and then collapsed again later.
– Average time to final collapse was 20 seconds.
– 8% of the animals took at least 60 seconds to collapse.
– A few animals took longer than 75 seconds to collapse.

These cattle did not have EEG electrodes connected to them, but I leave it to the reader to determine for themselves whether they think it likely that an animal that has had it’s neck sliced open, which collapses, and then is able to regain its feet for a period of time up to a minute or so, is unable to feel any pain or distress.

Bleeding Into The Airways

The same group published a paper back in 2008 looking at the prevalence of bleeding into the sliced open trachea, comparing the prevalence of blood in the trachea, the bronchi and the lower airways in animals that were stunned, or animals killed by ritual slaughter without stunning [5]. They found that:

– Stunned animals stopped breathing almost immediately.
– Blood in upper trachea:   Halal = 58% vs stunned = 21%
– Blood in bronchi:               Halal = 69% vs stunned = 31%
– Bloody froth in airways:      Halal = 19% vs stunned = 0%

(It was considered that bloody froth was indicative of the presence of blood in the distal or lower airways). The relevance here is that any extra fluid in one’s airways is extremely uncomfortable. Think about the last time you swallowed something and it went down “the wrong way”; even a small amount of saliva that has been aspirated (breathed in) will have you coughing madly for a while and it is most certainly not a pleasant experience***. Again, I leave it to you, the intrepid reader, to decide whether you think drowning in your own blood while you try to breathe for 20-60 seconds is a candidate for a Fun And Humane Ways To Spend Your Time award.

EEG Monitoring In Slaughtered Animals

The limited and poorly reported EEG data that was the subject of part of Schulze’s 1978 paper have been discussed above. Others have since explored the same avenue of investigation. In 1988 Daly et al. investigated the  time to loss of evoked EEG responses in cattle that were either stunned or ritually slaughtered [6]. This was a small study (n = 16) and the results were:

For stunned animals:
– 100% of stunned animals irreversibly lost evoked responses immediately.
– Average time from cutting of the neck to loss of all electrical activity was < 59 seconds.

For ritually slaughtered animals:
– Evoked responses were lost from 20 to 126 seconds (average 55 to 77 seconds) after cutting of the throat.
– Average time from cutting of the neck to loss of all electrical activity was 75 seconds.

Both visual and somatosensory evoked potentials were measured (somatosensory = touch/pain sensation from the body’s structures). The results indicate that the stunned animals lost the capacity for their brain to sense or react to any further sensory input (such as having one’s throat sliced open) after they were stunned. The ritually slaughtered animals demonstrated an ability to sense and react to sensory input (including pain) for an average of 77 seconds (somatosensory input). The time to flatlining of the EEG was also longer in the ritually slaughtered animals.

Gibson et al. looked at EEG changes in bolt-stunned cattle in 2009, and found that changes in cerebrocortical activity sufficient to produce insensibility occurred at 0-14 seconds after stunning [7]. The same group also found that EEG responses seen in animals ritually slaughtered, and thought to be due to noxious stimulus (i.e. the pain of having their necks sliced open) were absent in animals killed in the same way after captive bolt stunning [8, 9].


In determining whether ritual slaughter or stunning is more humane, the pivotal question is what and for how long does the animal feel before it dies. The available evidence, as detailed above, reflects the following:

– Both methods kill the animal in about the same time (as one might expect since exsanguination is the mode of death in both cases), though brain death (flat EEG) may occur faster in stunned animals.

– Ritually slaughtered animals continue to breathe as they begin to exsanguinate, whereas stunned animals do not. Ritually slaughtered animals consequently aspirate or inhale significant quantities of their own blood during their final minutes. This is almost certainly highly unpleasant.

– Highly sensitive EEG data demonstrates the persistence of the ability to sense and react to pain for an average of 77 seconds in ritually slaughtered animals. Stunned animals show no EEG evidence of evoked responses to physical stimuli of any sort, from the moment of stunning onwards.

– A significant proportion of ritually slaughtered animals are able to regain their feet after initial collapse, indicating ongoing brain function and consciousness. It is highly unlikely that they can stand up, yet not be aware of pain and distress.

While the origins of ritual slaughter as advocated by Judaism and Islam have their roots in a desire for the most humane treatment possible for livestock animals, modern insistence on such traditional slaughter methods have become, like so many other aspects of religious dogma and practice, inherited hand-me-downs from a more ignorant time. Such practices seem insisted upon predominantly (if not wholly) through a desire to adhere blindly to tradition, rather than for any practical or rational reason. Times have changed, and the best way of doing things millennia ago is not necessarily still the best way.

Attempts to mount a rational argument in favour of the ritual slaughter of cattle, while welcomed, are simply not supported (and are actively refuted) by the preponderance of available published, peer-reviewed evidence. The stunning of cattle immediately prior to slaughter clearly involves less suffering for the animal, and it is incumbent upon us as sentient fellow animals who understand all too well the nature of anxiety, pain and fear to do what we can to minimise that suffering. Ideally we could all become vegetarians overnight, but in a world where untold thousands of cattle will be killed every day for our benefit, the least we can do is make an effort to end their lives as swiftly and painlessly as possible.


Addendum:   It should be noted that all of the above evidence and discussion thereof is based on the more or less perfect execution of ritual slaughter technique. That is, expert incision of the anterior neck structures with a very sharp knife by a skilled operator, in one smooth continuous motion, with the animal standing up and contained. i.e. the very best circumstances. Such conditions are not always met and, indeed, in the facilities seen in the Four Corners story, it appeared none of these conditions was met. The suffering of animals in such circumstances is almost certainly far worse than that noted in the arguments above.


* Yes folks, the primary meaning of “moot” is debatable, _not_ resolved or inconsequential.

** My minions are working on finding the original data. I’ll post an update when it’s available.

*** This is predicated on the assumption that at least some of you are as amazingly physiologically uncoordinated as I am and that you do, indeed, accidentally inhale your own body fluids and/or drinks now and then.



2. Schulze W, Schultze-Petzold H, Hazem AS, Gross R.  1978, “Experiments for the objectification of pain and consciousness during conventional (captive bolt stunning) and religiously mandated (“ritual cutting”) slaughter procedures for sheep and calves”, Deutsche Tierärztliche Wochenschrift 85(2) pp. 62-6.

(English translation: )


4. Gregory NG, Fielding HR, von Wenzlawowicz MV, von Holleben KV. 2010, “Time to collapse following slaughter without stunning in cattle”, Meat Sci. 85(1) pp. 66-9.

5. Gregory NG, Wenzlawowicz MV, Holleben KV. 2008, “Blood in the respiratory tract during slaughter with and without stunning in cattle”, Meat Sci. [Epub 10 Dec 08].

6. Daly CC, Kallweit E, Ellendorf F. 1988, “Cortical function in cattle during slaughter: conventional captive bolt stunning followed by exsanguination compared with shechita slaughter”, Vet.Rec. 122(14) pp. 325-9.

7. Gibson TJ, Johnson CB, Murrell JC, Mitchinson SL, Stafford KJ, Mellor DJ. 2009, “Electroencephalographic responses to concussive non-penetrative captive-bolt stunning in halothane-anaesthetised calves”, NZ Vet.J. 57(2) pp.90-5.

8. Gibson TJ, Johnson CB, Murrell JC, Mitchinson SL, Stafford KJ, Mellor DJ. 2009, “Amelioration of electroencephalographic responses to slaughter by non-penetrative captive-bolt stunning after ventral-neck incision in halothane-anaesthetised calves”, NZ Vet.J. 57(2) pp. 96-101.

9. Mellor DJ, Gibson TJ, Johnson CB. 2009, “A re-evaluation of the need to stun calves prior to slaughter by ventral-neck incision: an introductory review”, NZ Vet.J. 57(2) pp. 74-6.



  1. Well thats all the theory….this is how it should be in practice:

    That is the way halal slaughter should be done. Yes often it isn’t – like 4 corners found out but that could be also said of non-halal slaughter-houses.

    I think a lot of the problem is that people now eat just too much meat and this means that the slaughter of animals is now completely industrialised and subsequently a bit cruel.

    Anyway that is my two cents worth.

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