The primary goal of euthanasia is to induce immediate and sustained loss of consciousness followed by death.1 Barbiturate overdose is an acceptable method for euthanasia of goats. Other acceptable methods include electrocution as well as gunshot and use of a PCB, the latter of which should be accompanied by an adjunctive method to ensure death. Barbiturates generally induce a smooth transition from consciousness to unconsciousness and death, and use of barbiturates may be the best option for some settings. Conversely, barbiturate overdose has disadvantages that include a need to restrain an animal for IV administration of the drug; both restraint and venipuncture can induce distress. In addition, a veterinarian must administer the drug, and proper carcass disposal is required to reduce the risk of drug residues to scavenger animals.1 Electrocution is an acceptable method of euthanasia when performed in accordance with established euthanasia guidelines from the AVMA1; however, electrocution requires trained personnel and specialized equipment to ensure safe and effective use in on-farm conditions.1
Gunshot and PCB or nonpenetrating captive bolt are physical methods capable of inducing immediate loss of consciousness and death, but the effectiveness of these devices is dependent on selection of the proper anatomic site and directional aim of the device. To cause immediate loss of consciousness and brain injury that leads to death, a PCB must damage the cerebral hemispheres as well as vital structures in the region of the brainstem (including the midbrain, pons, and medulla oblongata).1–5 Consciousness is also altered by direct damage to regions of the diencephalon, including the thalamus and hypothalamus, caudal portion of the pituitary gland, and pineal gland.5 Injury to the brain is caused by the bolt's entry into the skull, which results in a massive increase in intracranial pressure followed by an equally substantial decrease in intracranial pressure.6 These pressure extremes cause widespread damage to nerves and blood vessels within the brain. Major damage also occurs within and peripheral to the path of the bolt. Shards of bone from the skull are often pushed deep into the brain, which increases destruction along the bolt pathway. Selection of the proper anatomic site and directional aim are important for successfully performing euthanasia.
Currently, recommendations regarding the proper anatomic site and directional aim for euthanasia of goats are imprecise and confusing. Given that euthanasia is a procedure producers often may be expected to perform consistently, albeit with minimal technical and anatomic training, it is critical the site be easy to identify and provide a consistent location for PCB device placement.
It has been suggested that the approach for use of a PCB device in polled sheep and goats be “from behind or from the top of the head at a point high up on the head an equal distance from the eyes and ears.”7 For horned sheep and goats, those authors recommended that the approach be “from the rear with the aim directed between the base of the horns toward the mouth.”7 If a firearm is used, it may be “aimed from the front just above the eyes on the midline, shooting towards the spine.”7 In any case, it is possible that these descriptions could result in inconsistent placement of a PCB device or firearm. For polled sheep and goats, the recommendations indicate the option of “behind” with no further guidance as to where the PCB device is to be placed, and a similar issue exists for polled sheep and goats that should be approached “from the rear.” Similarly for the sites in horned sheep and goats, it is recommended that the projectile be directed at the “mouth” or “spine,” both of which are elongated anatomic structures (> 7.6 cm), which can result in uncertainty regarding the exact location for placement and major differences in the penetration angle of the projectile.
Guidelines from the Humane Slaughter Association8 indicate that all goats should be treated as though they have horns for placement of a PCB device. The muzzle should be placed “behind the bony mass on the midline and aimed towards the base of the tongue.”8 This recommendation fails to specify the exact meaning of “the bony mass” and how far “behind” this mass to place the PCB device. Furthermore, although the “base of the tongue” is a slightly more specific description, the reference to a deep anatomic structure that is not readily visible on the skin surface requires at least some knowledge of veterinary anatomy. This is likely to result in inconsistent placement because of the various degrees of technical skill of those performing euthanasia.
Similarly, information for small ruminants (both sheep and goats) in the 2013 AVMA euthanasia guidelines1 was based on recommendations made for sheep in the 2011 World Organization for Animal Health terrestrial animal health code.9 The AVMA guidelines1 indicate that the location for placement of a PCB device or the entry of a projectile is similar for sheep and goats. Accordingly, the site for polled sheep is described as “at or slightly behind the poll aiming toward the angle of the jaw (ie, base of the tongue).”1 The site for heavily horned rams or ewes is listed as “high on the forehead aiming toward the foramen magnum (or spinal canal) or, alternatively, at or slightly behind the poll (ie, behind the bony ridge between the horns) aiming toward the angle of the jaw or base of the tongue”.1 These landmarks pose issues similar to those described previously, including the use of jargon-based anatomic locations (ie, poll) and the use of terms (ie, deep) and hard to locate anatomic structures (ie, foramen magnum and base of the tongue).
Concerns related to ambiguous jargon-based anatomic locations (eg, poll) were highlighted in a recent study10 designed to compare PCB and nonpenetrating captive bolt methods. The authors recommended that “the muzzle be placed flush on the dorsal midline of the head at the level of the external occipital protuberance (poll) and aimed downward toward the cranial most portion of the intermandibular space.”10 Examination of the use of the term “poll” reveals that the recommendations of the AVMA euthanasia guidelines1 and that study10 are not referring to the same anatomic location (ie, “behind the bony ridge between the horns”1 and “the external occipital protuberance”10). These types of discrepancies result in an increased risk of poor placement of a PCB and inconsistent success for euthanasia.
Because of the desire to have landmarks that can be quickly and accurately identified by persons performing euthanasia (who may have various skills and amounts of training) and that can consistently be used to identify an appropriate site for placement of a PCB device, the AVMA Guidelines on Humane Slaughter11 offer a recommendation that is based on a study12 conducted at Iowa State University. Observations from that study12 suggested the preferred anatomic site was the intersection of 2 lines, each of which was drawn from the lateral canthus of 1 eye to the center of the base of the opposite ear while holding the muzzle perpendicular to the skull over the intended site.
Discrepancies in anatomic locations and vague descriptions of anatomic sites reported in the literature have led to confusion among producers and veterinarians who are required to euthanize goats. Therefore, the purpose of the study reported here was to describe specific external anatomic landmarks and confirm that they will result in the proper orientation for aiming a PCB device in horned and polled goats to maximize the likelihood of causing damage to the brainstem when euthanizing these animals. Furthermore, we intended to validate that use of a PCB at the described site in anesthetized goats would consistently result in euthanasia of these animals.
The authors declare that there were no conflicts of interest.
Penetrating captive bolt
CASH special captive bolt with heavy-duty medium bolt assembly 4121 K3, Accles and Shelvoke, Birmingham, West Midlands, England.
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