Stunning and killing cattle humanely and reliably in emergency situations--a comparison between a stunning-only and a stunning and pithing protocol.

An outbreak of an infectious animal disease that threatens the national herd is an emergency situation. Part of the strategy to contain and eventually eradicate the causal agent is targeted depopulation of the infected animals and those animals in close contact or proximity that potentially may be infected. “When animals are killed for disease control purposes, methods used should result in immediate death or immediate loss of consciousness lasting until death; when loss of consciousness is not immediate, induction of unconsciousness should be non-aversive and should not cause anxiety, pain, distress or suffering in the animals” (1) (Table 1). Table 1 World Organization for Animal Health acceptable methods for killing animals for disease control purposes (1) Under field conditions, fulfilling these requirements is challenging. The 2001 foot and mouth disease outbreak in Britain required the culling of 6 million livestock (2), 4 million of which needed to be destroyed on-farm. Firearms In a mass depopulation scenario involving adult cattle in Canada, firearms are readily available. A bullet fired from a rifle of appropriate caliber used by a good marksman is capable of reliably killing adult cattle through the massive transfer of energy and the resulting damage to the brain (3). The free bullet first stuns and then kills the animal in very quick succession (4). Safety precautions may allow the use of free bullets in open areas. Whenever firearms are used in enclosed spaces or when the animals stand on hard surfaces, free bullets may exit the carcass with sufficient speed to ricochet from solid objects and pose a risk to personnel and other animals. Such a situation also exists whenever cattle have to be destroyed inside a vehicle (emergency response after a livestock truck rollover; a nonambulatory animal that must be stunned prior to being unloaded). Using an alternative to the free bullet may be preferable in such cases. A penetrating captive bolt, with a sufficiently high bolt speed, in good state of repair, and used properly will stun an animal. Death may result as a consequence of the physical damage to the brain caused by penetration of the bolt, but death is not a guaranteed outcome. The immediate question is, What percentage of animals is killed by a captive bolt? One benchmark is provided by audit reports — the best slaughter plants under the best conditions average 97% to 98% successful stuns (5). “Successful” does not mean that these stuns were irreversible or that the animal was killed. The animals were rendered insensible between stunning and death through exsanguination (stun-stick interval). In one study conducted in a controlled slaughterhouse environment, approximately 1.2% of bulls and cull cows returned to sensibility after captive bolt stunning, prior to being hoisted onto the rail (6). According to another study conducted in abattoirs in the UK, 6.6% of 1284 steers and heifers were stunned poorly; 1.7% of 628 cull cows were stunned poorly; but young bulls appeared to be particularly hard to stun correctly and 53.1% of 32 bulls in the study were stunned poorly (7). In a disease control situation, the work environment is different from that of an abattoir. Animals may not be well restrained and lighting conditions may be inadequate, both situations making accurate aiming of the captive bolt gun more difficult. Operators may be increasingly fatigued due to the unusually high workload and the physical and psychological demands of emergency response-type work in a disease outbreak situation. Stunning equipment may not receive the same amount of maintenance and care in the field, as is expected in a slaughterhouse environment. Therefore, it is to be expected that the percentage of successful stuns will be lower under field conditions than in a slaughterhouse and to ensure death, the animal needs to be bled out as soon as possible after the captive bolt shot. However, from a disease control standpoint, dissemination of body fluids in the open harbors the risk of dispersing a disease agent; thus, this may not be a viable option. Shooting animals with what is essentially a stunning device in the hope that the stunning is irreversible and will lead to death amounts to a gamble and would run contrary to the OIE recommendations. Given the large numbers of animals that may have to be destroyed, even a low percentage of ineffective kills that lead to animals returning to sensibility is unacceptable from an animal welfare standpoint and undesirable in the context of efficient disease control operations; moreover, the sight of severely wounded animals regaining sensibility, showing coordinated movement, and even attempting to get up would be distressing for onlookers and for personnel who have to restun and kill such animals. Pithing is an alternative to exsanguination. The effectiveness of a pithing protocol compared with a stunning-only protocol for ensuring permanent insensibility and death has, to the authors’ knowledge, not been studied before. The purpose of this study was to determine, under field conditions, whether a captive bolt shot causes irreversible stunning and death in cattle with a reliability that is acceptable from an animal welfare standpoint and whether the use of a pithing rod could increase the success rate without compromising operator safety.

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