What 9 peer-reviewed scientific papers actually say about shechita
By: Richard Rabkin,
Managing Director
For the last number of years, shechita has been under an intense microscope – in Canada and around the world. Here at home, our dispute with the Canadian Food Inspection Agency (CFIA) over its restrictive regulations unfortunately moved into litigation. At the time of writing, we continue to negotiate with the CFIA in the hope of reaching a resolution that protects both animal welfare and the integrity of shechita.
The litigation taught us an important lesson. It was not enough to explain the halachic safeguards of shechita, to point to centuries of practice, or even to produce respected experts. If regulators, courts and international standard-setting bodies were to reconsider entrenched assumptions, the scientific case had to appear in peer-reviewed academic journals – where independent experts examine the methods, challenge the conclusions and require revisions before publication.
That realization began a long, complicated and costly process. Cardiologists, neurologists, veterinarians, neurophysiologists, engineers and animal-welfare experts have worked together to revisit old experiments, test modern claims and ask the right scientific questions. Nine papers have now been published. They do not all study the same issue, but together they tell a remarkably consistent story: a properly performed shechita causes a catastrophic and irreversible collapse in the blood supply needed for conscious brain function; loss of consciousness follows rapidly; movements after the cut do not necessarily indicate consciousness or mental awareness; and some common arguments used against shechita rest on measurements that do not actually prove conscious pain.
The Nine Scientific Papers, in Plain English
The blood-flow question
The first paper, published in the Journal of the American Veterinary Medical Association, was written by my father, Dr. Simon W. Rabkin, a cardiologist and professor of medicine at the University of British Columbia. Critics had argued that, even after the carotid arteries are cut, blood might continue reaching a cow’s brain through the vertebral arteries. They also suggested that so-called “false aneurysms” might block bleeding and delay unconsciousness. After reviewing the experimental literature and calculating the resulting blood flow, he found that cerebral blood flow falls to less than 5% of normal within seconds – far below the level needed to sustain brain function. Blood flow to the brain is dependent on blood pressure if blood pressure is zero it doesn’t matter if 30% of a cow’s blood flow to the brain is from vertebral arteries. Of course, 30% times zero is zero! He also found that the published images did not establish true false aneurysms or show that they meaningfully delayed blood loss. Therefore, the brain is rapidly deprived of the circulation needed for awareness and conscious pain; movements seen afterward cannot, by themselves, mean that the animal remains conscious or is suffering.
A second mechanism: air embolism
My father’s second paper, published in the Canadian Veterinary Journal, examined something largely overlooked in the shechita debate. When the jugular veins are opened, air can be drawn into the circulation by the heart’s pumping action. Air reaching the right side of the heart can create an “air lock” that sharply impairs circulation; air bubbles that pass through the lungs can also enter the arterial circulation and contribute to brain ischemia. This does not replace blood loss as the main explanation. It identifies an additional, well-known medical mechanism that can accelerate circulatory collapse and death after the incision. Therefore, air embolism provides another reason the loss of circulation after shechita is rapid and irreversible, rather than a prolonged period of conscious suffering.
How quickly is consciousness lost?
In the American Journal of Veterinary Research, Jacob R. Hascalovici, Hyman M. Schipper, Joe M. Regenstein, Stuart D. Rosen, Ari Zivotofsky, Guy St-Jean, Simon Freilich, Thomas J. Morrison, Simon W. Rabkin and Sheryl Haut systematically reviewed 15 studies addressing loss of consciousness in cattle after slaughter without stunning. They ranked four as high quality, three as medium quality and eight as low quality. The highest-quality evidence consistently showed loss of consciousness within 10 seconds when the procedure was performed correctly under low-stress conditions. The review separated stronger evidence from weaker evidence instead of treating every measurement as equally reliable. Thus, if an animal moves after losing consciousness, that movement is not proof of pain; the strongest evidence indicates that the capacity for conscious experience disappears rapidly.
A virtual cow confirms the physiology
In the American Journal of Veterinary Research, mechanical engineer Asher Benchimol, veterinarian Thomas Parmentier, neurologist Jacob Hascalovici and engineer David Vidal published “Impact of carotid artery sectioning on cerebral blood flow in bovines: a numerical hemodynamic study.” This was not another literature review. The researchers built a detailed computer model of the bovine cerebrovascular system in COMSOL Multiphysics using established anatomy, vessel dimensions, blood pressure and fluid-dynamics equations. They simulated circulation before, during and immediately after both carotid arteries were severed, including different levels of possible carotid blockage. The model predicted a near-instantaneous loss of approximately 99% of cerebral blood flow and pressure. It also showed why the intact vertebral arteries do not rescue the brain: their remaining flow is redirected through connecting vessels away from the brain and toward the open carotids. Even simulated carotid occlusions did not materially restore cerebral perfusion or delay its collapse. The model independently confirms the physiology described in the review papers: once the major vessels are severed, the cortex almost immediately loses the pressure and blood flow required for consciousness. Reflexive movement may continue, but the animal cannot consciously experience pain without functioning brain (cortical) circulation.
Do the vertebral arteries keep the brain alive?
In Frontiers in Veterinary Science, Jacob R. Hascalovici, Paolo Pozzi, Kathleen Yvorchuk, Guy St-Jean and Stuart D. Rosen examined 13 studies dealing specifically with the vertebral arteries – the vessels at the back of the neck that are not cut during shechita. Across the available evidence, vertebral pressure and flow dropped to negligible levels after the incision, and much of the residual flow was diverted away from the cerebral cortex. A pipe may remain physically connected to the brain, but that does not mean it carries enough blood, at enough pressure, in the right direction, to support consciousness. The review concluded that vertebral flow is unlikely to sustain cortical function or delay loss of consciousness. As a result, although an animal may potentially move after shechita, it is in part because of spinal reflexes as its cerebral cortex is not receiving the blood supply needed for awareness and it cannot actually be experiencing conscious pain.
The hidden vulnerability of stunning
In The Veterinary Journal, my father, Dr. Simon W. Rabkin, published “Blood pressure responses to captive bolt and electrical stunning in sheep and cattle: a systematic review.” The paper examined a question often omitted from comparisons between shechita and conventional slaughter: what happens to an animal’s blood pressure after the stun? A stun can produce immediate unconsciousness, but unless it also stops the heart it is potentially reversible; bleeding must follow quickly enough to ensure that the animal dies before consciousness can return. Dr. Rabkin searched for studies that directly measured systemic arterial blood pressure after electrical or captive-bolt stunning. Blood pressure increased in every study except one using halothane anesthesia – a drug that lowers pressure and blunts the body’s stress response. The rise in blood pressure appeared within seconds. This matters because blood pressure is the main force driving blood to the brain. In human and veterinary trauma medicine, maintaining pressure after brain injury can preserve brain viability. In the slaughter setting, the same response may help explain why an incompletely stunned animal can regain consciousness. Therefore, a stun should not be judged only by whether it renders the animal unconscious at the first instant. The full two-step stun-and-bleed process can fail if the stun is ineffective, begins to wear off or bleeding is delayed. Proper shechita, by contrast, begins irreversible exsanguination in the same act that collapses cerebral perfusion. This paper therefore provides a scientific basis for arguing that, under real-world conditions, shechita may even offer a welfare advantage over conventional stunning.
[Photo caption: Dr. Rabkin presenting his research at a shechita conference at the Ministry of Agriculture in Israel.]
Are inspectors looking for the right signs?
In Frontiers in Veterinary Science, Jacob R. Hascalovici, Ruth Woiwode, Hyman M. Schipper and Joane Parent reconsidered the physical signs used to decide whether an animal is conscious. Awareness and conscious pain require a functioning cerebral cortex. Yet several regulatory indicators – such as certain eye, breathing or postural reflexes – arise from the brainstem or spinal cord and can persist after cortical function has been lost. The authors proposed that rules for shechita should instead focus on signs suited to its physiology, including confirmation that both carotids have been severed and that continuous, high-volume bleeding is occurring. Kicking, paddling or another brainstem or spinal reflex after the cut should not be mistaken for conscious suffering; those movements can occur after the brain (cortex) has ceased functioning.
What direct brain recordings show
In Frontiers in Veterinary Science, Sheryl R. Haut, Thomas Parmentier, Robert S. Fisher and Nofal M. Khalil reviewed nine studies using EEG, electrocorticography and related techniques. These tools record the brain’s electrical activity; electrocorticography is generally more reliable because its electrodes are placed closer to the brain and are less affected by the skull and movement. In the strongest studies, electrical patterns consistent with loss of consciousness appeared between 4.4 and 13 seconds after the incision, with average values between 7.5 and 10.8 seconds. The authors concluded that the best available electrophysiological evidence supports rapid loss of consciousness and explained why less reliable surface recordings sometimes produced longer estimates. Therefore, the most direct objective brain evidence supports rapid unconsciousness, and movements occurring after that point cannot establish that the animal is consciously experiencing pain.
Can an EEG prove that an animal feels pain?
In the American Journal of Veterinary Research, Simon Freilich, Sheryl R. Haut, Jeffrey S. Mogil, Paolo Pozzi and Jacob R. Hascalovici addressed one of the most emotionally powerful claims in this debate: that EEG changes after the neck cut prove the animal experiences pain. After reviewing nine studies, they concluded that the evidence does not support that leap. A noxious event can trigger nociception – process of detecting and responding to harmful or damaging stimuli without consciously appreciating pain. Pain is an experience and requires preserved consciousness and integrated cortical function. The observed EEG changes could instead reflect the brain’s rapidly deteriorating blood supply and metabolism. Therefore, EEG changes alone cannot be cited as proof that an animal consciously feels pain, especially when the same evidence shows rapid failure of the cortical function required to experience it.
What the Evidence Means
No single paper answers every question, but the strength lies in the convergence of different disciplines. Cardiovascular measurements, a numerical blood-flow model, neuroanatomy, neural electrophysiology and reviews of consciousness indicators all point in the same direction. Properly performed, shechita rapidly deprives the cerebral cortex of the blood flow and blood pressure required for awareness. It is irreversible.
Is It Worth It?
Some people ask whether nearly three years of legal battles, advocacy and scientific publication have been worth the effort. We now have our first clear sign that the work is bearing fruit. Great Britain’s Food Standards Agency recently placed an important conclusion on the official record: “Our analysis found no clear evidence that animal welfare breaches are more or less likely to occur during non-stun slaughter compared to stunned slaughter.“
That is careful government language. But it is meaningful: the government’s own analysis did not support the assumption that non-stun slaughter produces more animal-welfare breaches. This is real progress.
Granted, the work is expensive. Research, statistical review, publication, translation, legal advocacy and engagement with regulators all require sustained effort and resources. We need continued financial support to keep moving this effort forward. The question is no longer whether the work is worth it. The early results show that it is. The real question is how do we ensure that this important work can continue to benefit Jewish communities in Canada and around the world. ∎
To support this effort, contact Samuel Herzog at [email protected]
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