• View in gallery

    Photograph of the sagittal section of the skull of a goat cadaver with the blade of a protractor placed to indicate the required trajectory of a PCB to make contact with the thalamus (partially obscured by the blade of the protractor) and midbrain tissues of the brainstem. The yellow band represents the line between the lateral canthus of the eyes.

  • View in gallery

    Schematic depictions of the method for determining the proper anatomic site for euthanasia of a polled goat (A) and horned goat (B) by use of a firearm or captive bolt device. The optimal site represents the intersection of 2 lines, each of which is drawn from the lateral canthus of 1 eye to the middle of the base of the opposite ear. (Adapted from AVMA. AVMA guidelines for the humane slaughter of animals: 2016 edition. Available at: www.avma.org/KB/Resources/Reference/AnimalWelfare/Documents/Humane-Slaughter-Guidelines.pdf. Accessed Jul 12, 2017. Reprinted with permission.)

  • View in gallery

    Photograph of the positioning of a PCB device perpendicular to the skull of a goat to improve the likelihood that the bolt will make contact with regions of the brainstem and thalamus. The yellow band represents the line between the lateral canthus of the eyes.

  • View in gallery

    Sagittal section of the skull of a polled goat (A) and a horned goat (B) that were anesthetized and subsequently euthanized with a PCB to confirm the anatomic site and directional aim for the device. A plastic rod was inserted after the confirmation of death to help identify the path of the bolt. Notice that the bolt damaged both the thalamus (T) and midbrain (M).

  • 1. AVMA. AVMA guidelines for the euthanasia of animals: 2013 edition. Available at: www.avma.org/KB/Policies/Documents/euthanasia.pdf. Accessed Jul 19, 2017.

    • Search Google Scholar
    • Export Citation
  • 2. Gregory NG, Lee CJ, Widdicombe JP. Depth of concussion in cattle shot by penetrating captive bolt. Meat Sci 2007;77:499503.

  • 3. Blackmore DK. Energy requirements for the penetration of heads of domestic stock and the development of a multiple projectile. Vet Rec 1985;116:3640.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4. Daly CC, Whittington PE. Investigation into the principal determinants of effective captive bolt stunning of sheep. Res Vet Sci 1989;46:406408.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5. Finnie JW, Manavis J, Blumberg PC, et al. Brain damage in sheep from penetrating captive bolt stunning. Aust Vet J 2002;80:6769.

  • 6. Gregory N, Shaw F. Penetrating captive bolt stunning and exsanguination of cattle in abattoirs. J Appl Anim Welf Sci 2000;3:215230.

  • 7. Longair JA, Finley GG, Laniel MA, et al. Guidelines for euthanasia of domestic animals by firearms. Can Vet J 1991;32:724726.

  • 8. Humane Slaughter Association. Captive bolt stunning of livestock, 2013 edition. Available at: www.hsa.org.uk. Accessed Jul 12, 2017.

  • 9. World Organisation for Animal Health (OIE). Chapter 7.6: killing of animals for disease control purposes. In: Terrestrial animal health code. 20th ed. Paris: OIE, 2011.

    • Search Google Scholar
    • Export Citation
  • 10. Collins SL, Caldwell M, Hecht S, et al. Comparison of penetrating and nonpenetrating captive bolt methods in horned goats. Am J Vet Res 2017;78:151157.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11. AVMA. AVMA guidelines for the humane slaughter of animals: 2016 edition. Available at: www.avma.org/KB/Resources/Reference/AnimalWelfare/Documents/Humane-Slaughter-Guidelines.pdf. Accessed Jul 12, 2017.

    • Search Google Scholar
    • Export Citation
  • 12. Plummer P, Shearer J, Ramirez A, et al. Penetrating captive-bolt euthanasia of goats: optimal shot placement and evaluation of polled and horned goats, in Proceedings. 47th Annu Conf Am Assoc Bovine Pract, 2014;177178.

    • Search Google Scholar
    • Export Citation
  • 13. Accles & Shelvoke. CASH universal stunning kit's quick reference guide and powerload selection chart. Birmingham, West Midlands, England. Available at: www.acclesandshelvoke.co.uk/. Accessed Nov 8, 2017.

    • Search Google Scholar
    • Export Citation
  • 14. Gibson TJ, Ridler AL, Lamb CR, et al. Preliminary evaluation of the effectiveness of captive-bolt guns as a killing method without exsanguination for horned and unhorned sheep. Anim Welf 2012;21:3542.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15. Derscheid RJ, Dewell RD, Dewell GA, et al. Validation of a portable pneumatic captive bolt device as a one-step method of euthanasia for use in depopulation of feedlot cattle. J Am Vet Med Assoc 2016;248:96104.

    • Crossref
    • Search Google Scholar
    • Export Citation

Advertisement

Determination of anatomic landmarks for optimal placement in captive-bolt euthanasia of goats

View More View Less
  • 1 Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Ames, IA 50011.
  • | 2 Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Ames, IA 50011.
  • | 3 Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Ames, IA 50011.
  • | 4 Department of Animal Science, College of Agriculture and Life Sciences, Iowa State University, Ames, IA 50011.
  • | 5 Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Ames, IA 50011.

Abstract

OBJECTIVE To determine the optimal anatomic site and directional aim of a penetrating captive bolt (PCB) for euthanasia of goats.

SAMPLE 8 skulls from horned and polled goat cadavers and 10 anesthetized horned and polled goats scheduled to be euthanized at the end of a teaching laboratory.

PROCEDURES Sagittal sections of cadaver skulls from 8 horned and polled goats were used to determine the ideal anatomic site and aiming of a PCB to maximize damage to the midbrain region of the brainstem for euthanasia. Anatomic sites for ideal placement and directional aiming were confirmed by use of 10 anesthetized horned and polled goats.

RESULTS Clinical observation and postmortem examination of the sagittal sections of skulls from the 10 anesthetized goats that were euthanized confirmed that perpendicular placement and firing of a PCB at the intersection of 2 lines, each drawn from the lateral canthus of 1 eye to the middle of the base of the opposite ear, resulted in consistent disruption of the midbrain and thalamus in all goats. Immediate cessation of breathing, followed by a loss of heartbeat in all 10 of the anesthetized goats, confirmed that use of this site consistently resulted in effective euthanasia.

CONCLUSIONS AND CLINICAL RELEVANCE Damage to the brainstem and key adjacent structures may be accomplished by firing a PCB perpendicular to the skull over the anatomic site identified at the intersection of 2 lines, each drawn from the lateral canthus of 1 eye to the middle of the base of the opposite ear.

Abstract

OBJECTIVE To determine the optimal anatomic site and directional aim of a penetrating captive bolt (PCB) for euthanasia of goats.

SAMPLE 8 skulls from horned and polled goat cadavers and 10 anesthetized horned and polled goats scheduled to be euthanized at the end of a teaching laboratory.

PROCEDURES Sagittal sections of cadaver skulls from 8 horned and polled goats were used to determine the ideal anatomic site and aiming of a PCB to maximize damage to the midbrain region of the brainstem for euthanasia. Anatomic sites for ideal placement and directional aiming were confirmed by use of 10 anesthetized horned and polled goats.

RESULTS Clinical observation and postmortem examination of the sagittal sections of skulls from the 10 anesthetized goats that were euthanized confirmed that perpendicular placement and firing of a PCB at the intersection of 2 lines, each drawn from the lateral canthus of 1 eye to the middle of the base of the opposite ear, resulted in consistent disruption of the midbrain and thalamus in all goats. Immediate cessation of breathing, followed by a loss of heartbeat in all 10 of the anesthetized goats, confirmed that use of this site consistently resulted in effective euthanasia.

CONCLUSIONS AND CLINICAL RELEVANCE Damage to the brainstem and key adjacent structures may be accomplished by firing a PCB perpendicular to the skull over the anatomic site identified at the intersection of 2 lines, each drawn from the lateral canthus of 1 eye to the middle of the base of the opposite ear.

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.

Materials and Methods

Sample

Two experiments were conducted, one that involved cadaveric goat skulls and the other that involved the use of anesthetized live goats. Skulls for the first experiment were obtained from cadavers of 8 mature goats. The goats comprised 7 females and 1 male. The females were 3 Saanen-cross goats (all of which were disbudded), 2 Alpine-cross goats (both of which were disbudded), and 2 Boer-cross goats (1 horned and 1 disbudded); the male was a Boer-cross goat with horns. The 10 goats for the second experiment comprised 4 males (3 Boer-cross goats with horns and 1 Saanen-cross goat that was disbudded), 5 females (all were Saanen-cross goats that were disbudded), and 1 intersex Saanen-cross goat that was disbudded. Goats were characterized as young (6 to 12 months old [n = 4]) and mature (≥ 2 years old [6]).

Cadaver skull experiment

Skulls from 8 mature goat cadavers were used to determine the ideal anatomic site for placement and directional aim of a PCB to cause damage to the midbrain region of the brainstem. Each skull was frozen and split longitudinally with a band saw into 2 equal sagittal sections. Investigators used superficial (ie, skin) sites and a metal protractor to determine the ideal anatomic site and trajectory for a PCB or free projectile to enter the brain and make contact with the brainstem in skulls of both horned and polled goats.

Anesthetized goat experiment

Variables determined in the first experiment for both horned and polled goat specimens were used in the second experiment to confirm accuracy of these sites for euthanasia of anesthetized goats. Ten goats scheduled for euthanasia at the conclusion of a teaching laboratory were used to validate the proposed anatomic sites for accuracy to disrupt brainstem tissues.

All goats were anesthetized with a combination of xylazine hydrochloride and ketamine hydrochloride before the start of the teaching laboratory. Goats were monitored by use of an ECG to record cardiac activity. After the teaching laboratory was completed, the anesthetized goats were positioned in sternal recumbency with their pelvic and thoracic limbs positioned beneath them as if they were lying naturally. A rope halter was placed on each goat's head; the halter was used to position the head as it would be in an alert recumbent animal (ie, the head was held approximately 30 cm above the floor and parallel to the floor). The halter was used to raise and adjust the angle of the head while an assistant placed a hand on the neck for stability and another on the muzzle of the animal to provide support.

The anatomic site used was the intersection of 2 lines, each of which was drawn from the lateral canthus of 1 eye to the middle of the base of the opposite ear. The PCB device was a pistol-design fitted with a heavy-duty medium-length bolt assembly.a A 0.25-caliber powder charge (ie, powerload)b was used on the basis of the recommendations in the reference guide provided by the manufacturer.13 The muzzle was held perpendicular to the skull, and the device was discharged.

Anesthetized goats were monitored after PCB discharge by use of auscultation with a stethoscope until the heartbeat was no longer audible and by use of ECG for a maximum of 15 minutes or until cardiac arrest was determined. After death was confirmed, a plastic rod the same diameter as the PCB was inserted into the hole created by the bolt to map its path. Heads were removed at the atlanto-occipital joint and placed in plastic bags; investigators were careful to avoid disturbing the plastic rod that followed the bolt's path. Heads were stored in a walk-in freezer at −20°C for approximately 5 to 7 days. Frozen skulls were prepared for examination by sagittal transection. In all cases, the section was adjacent to or through the center of the plastic rod, which allowed visual identification of the depth of penetration and brain structures damaged by the bolt.

Results

Cadaver skull experiment

Examination of sagittal sections of cadaver skulls was used to identify brain structures (Figure 1). Results of these examinations indicated that the ideal anatomic site was at the intersection of 2 lines, each of which was drawn from the lateral canthus of 1 eye to the middle of the base of the opposite ear (Figure 2). Furthermore, the muzzle of the PCB device should be placed perpendicular to the site (Figure 3).

Figure 1—
Figure 1—

Photograph of the sagittal section of the skull of a goat cadaver with the blade of a protractor placed to indicate the required trajectory of a PCB to make contact with the thalamus (partially obscured by the blade of the protractor) and midbrain tissues of the brainstem. The yellow band represents the line between the lateral canthus of the eyes.

Citation: American Journal of Veterinary Research 79, 3; 10.2460/ajvr.79.3.276

Figure 2—
Figure 2—

Schematic depictions of the method for determining the proper anatomic site for euthanasia of a polled goat (A) and horned goat (B) by use of a firearm or captive bolt device. The optimal site represents the intersection of 2 lines, each of which is drawn from the lateral canthus of 1 eye to the middle of the base of the opposite ear. (Adapted from AVMA. AVMA guidelines for the humane slaughter of animals: 2016 edition. Available at: www.avma.org/KB/Resources/Reference/AnimalWelfare/Documents/Humane-Slaughter-Guidelines.pdf. Accessed Jul 12, 2017. Reprinted with permission.)

Citation: American Journal of Veterinary Research 79, 3; 10.2460/ajvr.79.3.276

Figure 3—
Figure 3—

Photograph of the positioning of a PCB device perpendicular to the skull of a goat to improve the likelihood that the bolt will make contact with regions of the brainstem and thalamus. The yellow band represents the line between the lateral canthus of the eyes.

Citation: American Journal of Veterinary Research 79, 3; 10.2460/ajvr.79.3.276

Anesthetized goat experiment

Application of the PCB at the intersection of 2 lines, each of which was drawn from the lateral canthus of 1 eye to the middle of the base of the opposite ear, resulted in immediate and permanent cessation of respiration in all 10 anesthetized goats. Mean time to loss of an auscultable heartbeat after discharge of the PCB was 643 seconds (range, 540 to 840 seconds). Electrical activity of the heart was detected by use of ECG in 7 of 10 goats for > 15 minutes, despite the fact there was no evidence of respiration throughout the entire period after PCB discharge.

Postmortem examination of sagittal sections from each of the anesthetized goats revealed that the PCB penetrated and damaged tissues within the midbrain region of the brainstem in all 10 goats (Figure 4). Visual assessment was used to determine that the bolt struck the thalamus and hypothalamus in 4 goats, midbrain and thalamus in 4 goats, and midbrain in 2 goats. The bolt did not directly damage the pons, cerebellum, or medulla oblongata in any of the goats.

Figure 4—
Figure 4—

Sagittal section of the skull of a polled goat (A) and a horned goat (B) that were anesthetized and subsequently euthanized with a PCB to confirm the anatomic site and directional aim for the device. A plastic rod was inserted after the confirmation of death to help identify the path of the bolt. Notice that the bolt damaged both the thalamus (T) and midbrain (M).

Citation: American Journal of Veterinary Research 79, 3; 10.2460/ajvr.79.3.276

Discussion

The objective of euthanasia is to induce an immediate loss of consciousness followed by death with no possibility of a return to consciousness. When physical methods are used, success depends on selection of the appropriate device (caliber and bullet for a firearm or powerload for a PCB device). Selection of an anatomic site and proper directional aim for a projectile that will be most likely to cause damage to the brain, and particularly the brainstem, are equally important. Previous recommendations regarding the anatomic site and directional aim of PCB devices are potentially confusing, especially for producers with minimal training in veterinary anatomy. Furthermore, this confusion has the potential to result in poor PCB device or firearm placement and ultimately compromise the humane procedures and effective euthanasia of an animal. The goal of the study reported here was to define anatomic landmarks on the basis of readily identifiable external structures that can be used to allow consistent device placement for the euthanasia of goats.

Results of the present study indicated that the suggested anatomic location and directional aim resulted in consistent physical damage and penetration of the midbrain or thalamus (or both). Although not actually part of the brainstem, the thalamus is anatomically located adjacent to the midbrain and serves vital functions as a relay center for nerve impulses between the brainstem and cerebrum. Consciousness is altered by physical damage to the diencephalon and brainstem and by focal and diffuse injury of the neural pathways connecting these tissues.5 The 4 anesthetized goats in which there was physical penetration of the bolt into the thalamus had an immediate cessation of respiration and rapid death. Similar results have been reported for cattle.6

Examination of sagittal sections of skulls from polled and horned goat cadavers suggested that the placement of a PCB device on the intersection of 2 lines, each of which was drawn from the lateral canthus (outside edge of the eyelid) of 1 eye to the middle of the base of the opposite ear, consistently caused disruption to the midbrain and thalamus. Results of the present study confirmed that holding the muzzle of the device perpendicular to this site directed the bolt into these brain regions. Previous studies5,14 indicated that despite the use of a consistent anatomic site, the trajectory of the bolt will differ substantially. However, as suggested by results for the present study, placing the captive bolt perpendicular to the skull allowed the operator more confidence for obtaining an appropriate directional aim because in most cases, the person will be standing above an animal and looking down at the animal's head, as opposed to looking at the lateral profile of an animal's head, which would be necessary to identify the anatomic structures used in some descriptions. Furthermore, keeping the muzzle perpendicular to the skull of an animal may allow the operator to better accommodate variable positions of the head (ie, nose up, nose straight forward, or nose down) that otherwise could complicate proper orientation.

The anatomic site identified in the study reported here is likely extremely similar to that identified in many previous descriptions. However, we emphasize that the use of easy-to-identify external anatomic landmarks and an x-marks-the-spot approach will allow for more consistent application of the method, regardless of the experience of the person performing the euthanasia. Furthermore, this site did not require the user to have knowledge of more complex anatomic terms such as external occipital protuberance, foramen magnum, and intermandibular space. The authors acknowledge that the anatomic sites suggested by others may be effective in the hands of experienced persons who have the skill and training that will enable them to properly position or directionally aim the muzzle of a PCB device toward regions of the brainstem.

Investigators of another study10 that involved use of a different approach were successful in causing damage to the brainstem of goat cadaver skulls when the muzzle of the captive bolt device was placed on the dorsal midline of the head at the level of the external occipital protuberance while the device was aimed downward toward the cranialmost portion of the intermandibular space. On the basis of the diagrams included in that study,10 they appeared to have identified a site that is essentially identical to the one described for the present study. Results of the study reported here helped to further refine the description of the anatomic site, which should facilitate more consistent application of the technique. Findings for the present study also supported those of the aforementioned study10 and confirmed that use of this anatomic site was effective for euthanasia of anesthetized goats.

In the present study, anesthetized goats were used to confirm that placement of the PCB device by use of the described anatomic landmarks would result in euthanasia without the use of an adjunctive method to ensure death (ie, exsanguination, pithing, or IV administration of a saturated solution of potassium chloride or magnesium sulfate). However, when this PCB method is to be used for euthanasia of conscious animals, we recommend use of an adjunctive method to ensure death until further studies can be conducted to determine whether this method can reliably be used for single-step euthanasia.1 In the anesthetized goats of the present study, there was a complete and immediate cessation of respiration after penetration of the PCB. This result was anticipated because of the damage to the thalamus and midbrain regions of the brainstem observed in the experiment conducted with the cadaver skulls. These observations agree with those of another study5 in which investigators conducted a similar study of the use of a PCB to euthanize 10 anesthetized sheep. In that study,5 6 sheep received respiratory assistance, and 4 did not. Respiration ceased immediately after firing of the PCB in all 10 sheep; the 4 sheep that did not receive respiratory assistance died within 10 minutes after penetration with the PCB, whereas the 6 sheep that received respiratory assistance survived beyond the allotted 2-hour study period. For the study reported here, the mean time from penetration with the PCB to loss of a detectable heartbeat by use of auscultation was 643 seconds (range, 540 to 840 seconds). This interval is slightly greater than the interval from PCB discharge to death in sheep5 and cattle.15

Poor shot placement has been identified as the most common cause of incomplete concussion, which emphasizes the fact that restraint is necessary to ensure penetration accuracy, particularly in horned rams.14 Restraint was not an issue in the study reported here because the goats were anesthetized. One anesthetized goat had a horn scur that prevented access to the desired anatomic site. Because the goat was anesthetized, the horn scur was removed so that the PCB device could be placed at the desired anatomic site and aimed in the preferred direction. In situations in which the horns interfere with placement at the intended site, we suggest that the PCB device be positioned as far forward between the horns as possible and the directional aim or angle be adjusted toward the midbrain accordingly. Moving the PCB device to the top of the head7 requires penetration through the hardest part of the skull, and there is more uncertainty about the directional aim.

There is limited information in the literature on specific procedures for euthanasia of goats. Recommendations on the preferred anatomic site and direction of aim of a PCB device or firearm differ and are often inconsistent. Results of the present study conducted with cadaver skulls and anesthetized goats confirmed the anatomic site for euthanasia by use of a PCB may be determined as the intersection of 2 lines, each of which is drawn from the lateral canthus of 1 eye to the middle of the base of the opposite ear. Our observations indicated that holding the muzzle of the PCB device perpendicular to the desired anatomic site for entry will direct the bolt toward the brainstem.

Acknowledgments

The authors declare that there were no conflicts of interest.

ABBREVIATIONS

PCB

Penetrating captive bolt

Footnotes

a.

CASH special captive bolt with heavy-duty medium bolt assembly 4121 K3, Accles and Shelvoke, Birmingham, West Midlands, England.

References

  • 1. AVMA. AVMA guidelines for the euthanasia of animals: 2013 edition. Available at: www.avma.org/KB/Policies/Documents/euthanasia.pdf. Accessed Jul 19, 2017.

    • Search Google Scholar
    • Export Citation
  • 2. Gregory NG, Lee CJ, Widdicombe JP. Depth of concussion in cattle shot by penetrating captive bolt. Meat Sci 2007;77:499503.

  • 3. Blackmore DK. Energy requirements for the penetration of heads of domestic stock and the development of a multiple projectile. Vet Rec 1985;116:3640.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4. Daly CC, Whittington PE. Investigation into the principal determinants of effective captive bolt stunning of sheep. Res Vet Sci 1989;46:406408.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5. Finnie JW, Manavis J, Blumberg PC, et al. Brain damage in sheep from penetrating captive bolt stunning. Aust Vet J 2002;80:6769.

  • 6. Gregory N, Shaw F. Penetrating captive bolt stunning and exsanguination of cattle in abattoirs. J Appl Anim Welf Sci 2000;3:215230.

  • 7. Longair JA, Finley GG, Laniel MA, et al. Guidelines for euthanasia of domestic animals by firearms. Can Vet J 1991;32:724726.

  • 8. Humane Slaughter Association. Captive bolt stunning of livestock, 2013 edition. Available at: www.hsa.org.uk. Accessed Jul 12, 2017.

  • 9. World Organisation for Animal Health (OIE). Chapter 7.6: killing of animals for disease control purposes. In: Terrestrial animal health code. 20th ed. Paris: OIE, 2011.

    • Search Google Scholar
    • Export Citation
  • 10. Collins SL, Caldwell M, Hecht S, et al. Comparison of penetrating and nonpenetrating captive bolt methods in horned goats. Am J Vet Res 2017;78:151157.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11. AVMA. AVMA guidelines for the humane slaughter of animals: 2016 edition. Available at: www.avma.org/KB/Resources/Reference/AnimalWelfare/Documents/Humane-Slaughter-Guidelines.pdf. Accessed Jul 12, 2017.

    • Search Google Scholar
    • Export Citation
  • 12. Plummer P, Shearer J, Ramirez A, et al. Penetrating captive-bolt euthanasia of goats: optimal shot placement and evaluation of polled and horned goats, in Proceedings. 47th Annu Conf Am Assoc Bovine Pract, 2014;177178.

    • Search Google Scholar
    • Export Citation
  • 13. Accles & Shelvoke. CASH universal stunning kit's quick reference guide and powerload selection chart. Birmingham, West Midlands, England. Available at: www.acclesandshelvoke.co.uk/. Accessed Nov 8, 2017.

    • Search Google Scholar
    • Export Citation
  • 14. Gibson TJ, Ridler AL, Lamb CR, et al. Preliminary evaluation of the effectiveness of captive-bolt guns as a killing method without exsanguination for horned and unhorned sheep. Anim Welf 2012;21:3542.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15. Derscheid RJ, Dewell RD, Dewell GA, et al. Validation of a portable pneumatic captive bolt device as a one-step method of euthanasia for use in depopulation of feedlot cattle. J Am Vet Med Assoc 2016;248:96104.

    • Crossref
    • Search Google Scholar
    • Export Citation

Contributor Notes

Address correspondence to Dr. JK Shearer (jks@iastate.edu).