Relationship of tissue dimensions and three captive bolt placements on cadaver heads from mature swine (Sus scrofa domesticus) > 200 kg body weight

Abstract

Three penetrating captive bolt (PCB) placements were tested on cadaver heads from swine with estimated body weight (BW) >200 kg (sows = 232.9 ± 4.1 kg; boars = 229.3 ± 2.6 kg). The objectives were to determine tissue depth, cross-sectional brain area, visible brain damage (BD), regions of BD, and bolt-brain contact; and determine relationships between external head dimensions and tissue depth at each placement. A Jarvis PAS – Type P 0.25R PCB with a Long Stunning Rod Nosepiece Assembly and 3.5 gr power loads was used at the following placements on heads from 111 sows and 46 boars after storage at 2-4° C for approximately 62 h before treatment: FRONTAL (F) – 3.5 cm superior to the optic orbits at midline, TEMPORAL (T) – at the depression posterior to the lateral canthus of the eye within the plane between the lateral canthus and the base of the ear, or BEHIND EAR (BE) – directly caudal to the pinna of the ear on the same plane as the eyes and targeting the middle of the opposite eye. For sows, the bolt path was in the plane of the brain for 42/42 (100%, 95% CI: 91.6-100.0%) F heads, 39/40 (97.5%, 95% CI: 86.8-99.9%) T heads, and 34/39 (87.5%, 95% CI: 72.6-95.7%) BE heads; for the heads that could reliably be assessed for BD damage was detected in 25/26 (96.2%, 95% CI: 80.4-99.9%) F heads, 24/35 (68.6%, 95% CI: 50.7-83.2%) T heads, and 5/40 (12.5%, 95% CI: 4.2-26.8%) BE heads. For boars, the bolt path was in the plane of the brain for 17/17 (100.0%, 95% CI: 80.5-100.0%) F heads, 18/18 (100.0%, 95% CI: 81.5-100.0%) T heads, and 14/14 (100.0%, 95% CI: 76.8-100.0%) BE heads; damage was detected in 11/12 (91.7%, 95% CI: 61.5-99.8%) F heads, 2/15 (13.3%, 95% CI: 1.7-40.5%) T heads, and 7/14 (50.0%, 95% CI: 23.0-77.0%) BE heads. Tissue depth was reported as mean ± standard error followed by 95% one-sided upper reference limit (URL). For sows, total tissue thickness was different (P < 0.05) between placements (F: 52.7 ± 1.0 mm, URL: 64.1 mm; T: 69.8 ± 1.4 mm, URL: 83.9 mm; BE: 89.3 ± 1.5 mm, URL: 103.4 mm). In boars, total tissue thickness was different (P < 0.05) between placements (F: 41.2 ± 2.1 mm, URL: 56.3 mm; T: 73.2 ± 1.5 mm, URL: 83.4 mm; BE: 90.9 ± 3.5 mm, URL: 113.5 mm). For swine > 200 kg BW, F placement may be more effective than T or BE due to less soft tissue thickness, which may reduce concussive force. The brain was within the plane of bolt travel for 100% of F heads with brain damage for 96.2% and 91.7% of F sow and boar heads, respectively.

History and best practices of captive bolt euthanasia for swine

“…The majority of peer-reviewed scientific publications on the topic at the time of this review were focused on NPCB euthanasia of neonatal (3 d of age or younger) pigs ( Casey-Trott et al, 2013 , 2014 ; Grist et al, 2017 , 2018a , 2018b ). At the time of this review, one peer-reviewed scientific publication exists related to the PCB euthanasia of grower-finisher swine ( Anderson et al, 2019 ) and two on the PCB euthanasia of breeding swine ( Anderson et al, 2021 ; Kramer et al, 2021 ). In addition, a thesis focuses on the NPCB and PCB euthanasia of six weight classes of swine, from 2 to 200 + kg ( Woods, 2012 ).…”

“… Anderson et al (2021) evaluated tissue depth measurements, brain area, brain contact plane, and brain damage associated with the frontal, temporal, and behind ear PCB placements on cadaver heads from mature sows and boars (BW > 200 kg). The authors concluded that the frontal placement appeared to be the most reliable with the PCB device used due to the least total tissue thickness, greatest potential target area, and high prevalence of brain damage.…”

“… Woods (2012) and Kramer et al (2021) both evaluated the efficacy of euthanasia with PCB devices for breeding swine. In contrast with the Anderson et al (2021) study, each of these studies was able to assess efficacy because live animals were used. Woods (2012) focused solely on the efficacy of a pistol-type PCB device in the frontal placement as a single-step euthanasia method for animals visually estimated to weigh more than 200 kg.…”

“…All three studies ( Woods, 2012 ; Anderson et al, 2021 ; Kramer et al, 2021 ) evaluated physical damage to the brain, while Woods (2012) and Kramer et al (2021) also evaluated hemorrhage. Of the eight animals that were effectively euthanized in the anesthetized stage of the work done by Woods (2012) , seven had physical penetration of the brain in the frontal location and one had physical penetration of the brain in the occipital location.…”

“…There was no difference in the TBI score produced from the different device types in the temporal or behind ear placements. Anderson et al (2021) assessed the presence of visual damage to the following regions of the brain: frontal lobe, parietal lobe, temporal lobe, occipital lobe, corpus callosum, diencephalon, mesencephalon, brainstem, and cerebellum. The regions of the brain assessed for each PCB placement were dependent upon the regions of the brain that were visible in the exposed cross-section of each head.…”