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United States Department of Agriculture

Agricultural Research Service

Title: Bioethics Symposium: Electric, Gas, or Religious Slaughter Alternatives

item Buhr, Richard

Submitted to: Southern Poultry Science Society Meeting Abstracts
Publication Type: Proceedings
Publication Acceptance Date: January 12, 2007
Publication Date: January 23, 2007
Citation: Buhr, R.J. 2007. Bioethics Symposium: Electric, Gas, or Religious Slaughter Alternatives. Southern Poultry Science Society Meeting Abstracts. P. 18-22.

Technical Abstract: The question that I was asked to address was: Is electrical stunning ethical? A stunning method would be considered ethical if the following criteria were attained. 1) Stunning results in a rapid onset of unconsciousness within a minimal time and with a minimal perception of pain. 2) The duration of the unconsciousness persists until death intervened. 3) There was a near zero occurrence of “under stunned” conscious broilers. Stunning by definition must permit the broiler to recover consciousness. Adequately electrically stunned broilers should recover consciousness, to the level of regaining the ability to maintain an erect posture, within 120 seconds following the stun. However, electrical stunning and exsanguination (bleeding) are integral steps in the slaughter of poultry and should be evaluated together in the progression to death. The term electric anesthesia is defined as, anesthesia induced from the passage of an electric current through the nervous system. This is analogous to electrical stunning and corresponds an unconsciousness level approximating the anesthesia Stage 3-medium. Electrical stunning does induce unconsciousness in poultry, but how can one determine the level of unconsciousness and therefore the inability of the broiler to perceive a pain stimuli? To answer this question the relationships of unconsciousness level and the perception of pain need to be described and agreed upon. Arthur Guedel in 1937 was the first to designate the four stages of anesthesia from consciousness through unconsciousness to death and the perception of pain. Guedel’s stages of anesthesia are listed below: Stage 1. Analgesia may be local or general - Loss of pain sensation, some disorientation or numbness, subject may remain conscious Stage 2. Excitement, delirium, epileptiform brain activity (human grand mal epileptic seizure in an unconscious state) - Loss of the ability to perceive pain, muscle reflexes are still present, involuntary struggling occurs, rapid respiration rate Stage 3. Surgical anesthesia, 3-planes Light - Skeletal muscle relaxation but reflexes are present, no voluntary muscle movement, regular respiration, palpebral and corneal reflexes present Medium - Skeletal muscle reflexes absent, palpebral reflex absent, corneal reflex sluggish Deep - Early overdose, respiration depresses (forced ventilation required), corneal reflex absent Stage 4. Medullary paralysis, death, overdose, flat line EEG - All reflexes absent, no initiation of respiration, cardiac function depressed Electroencephalograms (EEGs) record brain waves by measuring the electrical activity of the brain and are very temporally precise. EEGs from brain implanted electrodes have been used to determine the level of consciousness and activity of subjects, including broilers (Kuenzel and Walther, 1978; VanKampen, 1979). Collier et al. (2003) reported the protocol to record EEGs from conscious and stunned broiler chickens using noninvasive cutaneous electrodes and telemetry. Using these techniques, Buhr et al. (2003) were successful in recording EEGs in broilers stunned (at low or high voltages) and bled as they proceded to death. This work is being continued by ARS-Mississippi State (Poultry Research Unit) with goals to delineate the levels of unconsciousness in broilers resulting from anesthetics and then comparisons are to be made to various commercial stunning methods. The American Veterinary Medical Association panel on euthanasia (2001) describes three physical methods for euthanasia appropriate for poultry: 1) stunning with an apparatus that assures passage of the current through the brain and followed immediately by a method that ensures death such as exsanguination, decapitation, or electrocution; 2) cervical dislocation by trained personnel, and 3) electrocution if the animal is first rendered unconscious (stunned). When cervical dislocation or decapitation is preceded by electrical stunning, there is no death struggle that typically occurs with cervical dislocation without prior stunning. Historically the level of unconsciousness and the associated inability to perceive pain has been evaluated in stunned broilers by the palpebral (eyelid) avoidance reflex or the absence of the limb withdrawal reflex when a distal pinch is applied. These methods are not easily applied or observed on shackle lines operating at speeds as high as 140 birds per minute. Recently we confirmed that spinal cord severing of stunned broilers on line could be used as an indication of the level unconsciousness. Stunned broilers (25 V DC at 500 Hz, brine stunner) were bled by severing both carotid arteries and the right jugular vein and then at 30-second intervals spinal cord severing was applied. From 30 through 120 seconds, when spinal cord severing was applied to stunned and bleeding broiler carcasses, no subsequent death struggle was induced. Therefore, electrical stunning followed by bleeding maintained unconsciousness through the time of death when spinal cord severing was applied. Additional experiments have revealed that electrical stunning durations as short as 2 seconds result in unconsciousness sufficient that immediate spinal cord severing and did not result in a subsequent death struggle. These results imply that the onset of unconsciousness by the application of electrical stunning is indeed rapid and when accompanied with bleeding, unconsciousness is maintained until death occurs within 120 seconds. The possibility of the occurrence of electrical immobilization, retaining the ability to sense and perceive pain but unable to respond to stimuli, can occur if the electrical current path does not reach the brain of the subject. Electrical immobilization does not appear to occur in electrically stunned broilers (using a brine stunner), since spinal cord severing following stunning and bleeding does not result in a death struggle. The limitations of brine stunners and the potential presence of electrical immobilization can also be answered by EEGs and should be evaluated under various stunning parameters. Skeletal muscular activity during bleeding prior to scalding is not necessarily an indication that the broiler is regaining consciousness since skeletal movements do occur during Stages 2 and in the light plane of Stage 3 anesthesia, when the ability to perceive pain is absent. Similarly, the occurrence of a cadaver indicates that a functional brain stem and cardiovascular system were present at the time the brain perceived an elevation in body temperature upon entering the scalder water. Two studies have concluded that “red-skin” cadaver chicken carcasses, are caused by the physiological response to elevated temperature when carcasses enter a scald tank (Heath et al. 1983; Griffiths and Purcell 1984). Unconscious broilers at Stage 3-Medium level of anesthesia would upon entering the scalder result in cadavers. The occurrence of skeletal movements during bleeding and cadavers upon scalding can occur as long as the broiler’s brain stem is functional, but at a level of unconsciousness that pain is not perceived. The occurrence of skeletal movements during bleeding and the occurrence of cadavers can both be completely eliminated if decapitation or spinal cord severing is applied following stunning, during bleeding and prior to scalding (Buhr et al., 2005). The determination of the ethical status of slaughter methods depends greatly on a critical review of the literature and that the results and conclusions agree with the subsequently published literature and the body of knowledge of physiology and anatomy. For example Dickens & Shackelford (1988) reported the electrical stunning reduced feather retentions force by 16 to 18%. However, in their experiments there were no controls, no non-stunned or gas stunned treatment groups. Their methodology erroneously plucked the big feather first and smaller feather after electrical stunning. Thi

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