Electromagnetic (EM) energy transmitting devises that operate in the microwave frequency have been approved by the American Veterinary Medical Association for the specific use in euthanasia of laboratory mice and rats and have been also applied to chickens. Units utilized for this method of euthanasia focus all EM (microwave) energy to the head of the animal targeting the brain for very rapid elevation of brain temperature. This increase in brain temperature results in denaturation of neural connections and very rapidly incapacitates all brain function; including any perception of pain. With this in mind, EM energy poses a possibility for the development of a new tool to be utilized when it becomes necessary to euthanize piglets. The primary objective of this project was to test the utilization of EM energy as a potential means of euthanizing piglets on the farm. Experiment 1 assessed whether or not EM energy could bring anesthetized piglets to death and Experiment 2 evaluated the consciousness, unconsciousness, post-EM energy exposure (EMEE), and death of piglets.
In Experiment 1, six anesthetized piglets were exposed to 40 s of EMEE. Prior to EMEE, heart rate, respiration rate, head surface temperature, and internal body temperature were recorded. Following EMEE, heart rate, respiration rate, head surface temperature, and mid-brain temperature were recorded. Prior to EMEE, internal body temperature was 37.7ºC and following EMEE intracranial temperature was 62.8ºC. Head surface temperature was higher (P < 0.01) after EMEE (32.7 vs. 69.2ºC, respectively). Moreover, respiration stopped in each piglet immediately following EMEE. Unassisted death occurred after heart rate ceased within 4.8 min after EMEE application in five of the six piglets.
Treatments in Experiment 2 included EMEE for 3, 6, or 9 s administered to 8 piglets per treatment (24 total). Electroencephalogram (EEG) and electrocardiogram were recorded during each stage of consciousness. Additionally, head surface and internal body temperatures were recorded before and after EMEE. State of consciousness and treatment interaction affected (P < 0.01) EEG amplitude and power. State of consciousness affected (P < 0.01) EEG frequency. Sex affected (P < 0.01) EEG amplitude. Further, piglets exposed to 9 s EMEE had higher (P < 0.01) body temperature compared with piglets exposed to 3 and 6 s EMEE (40.6 vs. 39.1 and 39.6ºC, respectively). Piglets exposed to 9 s EMEE had higher post EMEE head surface temperature than piglets exposed for 3 s (39.7 vs. 34.9ºC, respectively). Moreover, heart rate was reduced (P < 0.01) from conscious to unconscious to after EMEE applications.
This research provides insight to the possibility of developing new techniques as well as the potential for improving current methods of euthanizing piglets. Our study is unique in its use of EEG analysis of piglets during consciousness, unconsciousness, and death. Our observations and analysis have aided in the establishment of baseline EEG values for piglets. With further research in this area and an increase in sample size, there is a possibility to improve on-farm husbandry and euthanasia techniques with regard to animal welfare. With further research, a new technique could be available to humanely euthanize piglets. Experiment 1 demonstrated that EM energy results in the death of a piglet and with modifications of our equipment and EEG data, we will be able to better understand the effects of EM energy on the sensibility of piglets. Based on the EEG data from this study, it would be recommended that future trials utilizing the same amount of EM energy expose the piglet in excess of six seconds. Since piglets were under a surgical plan of anesthesia when exposed to EM energy, it is still unclear as to the actual effect EM energy has on the sensibility of piglets and potential for perception of pain during application. Future research is necessary to provide a better understanding regarding attaining pain insensibility. Once the temperature critical limit for brain inactivation (establishment of pain insensibility) has been determined, the duration of electromagnetic energy exposure is irrelevant. Energy could be administered for sufficient duration to achieve complete brain denaturation and physical death.
