Abstract
Penetrating captive bolt (PCB) is a common method of euthanasia for mature sows but limited data exist regarding PCB efficacy for these animals. Two PCB placements were evaluated on cadaver heads from sows with an estimated body weight (BW) of >200 kg (Mean ± SD: 225.4 ± 21.1 kg). The objectives were to determine the thalamic diameter, distance to the thalamus, effective angle, and tissue depths associated with the FRONTAL and BEHIND EAR PCB placements for sows >200 kg. Cadaver heads were obtained from sows (n = 60) from a regional slaughter establishment following electrical stunning, then cooled at 2-4°C for approximately 64 h. Heads were randomly assigned to one of six treatments (n = 10): FRONTAL-INLINE, FRONTAL-PISTOL, FRONTAL-NO SHOT, BEHIND EAR-INLINE, BEHIND EAR PISTOL, BEHIND EAR-NO SHOT. The FRONTAL placement was 3.5 cm superior to the optic orbits at midline; the BEHIND EAR placement was directly caudal to the pinna of the ear on the same plane as the eyes and targeting the middle of the opposite eye. For INLINE treatments, a Jarvis PAS-Type C 0.25R Super Heavy Duty PCB with a Long Bolt and 6.0 GR power load was used. For PISTOL treatments, a Jarvis PAS-Type P 0.25R with a Long Stunning Rod Nosepiece Assembly and 3.5 GR power load was used. All heads were split along the bolt path or theoretical bolt path using a band saw. Thalamic diameter, distance to thalamus, and effective angle were measured only on heads that received the NO SHOT treatment. Tissue depths were measured only for the heads that received the INLINE and PISTOL treatments. Comparisons between PCB placements were made using Student’s T Tests. All results are reported as Means±SE. There was no evidence to support a difference (P = 0.5163) in thalamic diameter between the FRONTAL (12.86 ± 0.40 mm) and BEHIND EAR (12.38 ± 0.60 mm) placements. The distance from the proper PCB placement to the thalamus was less (P < 0.0001) for the FRONTAL placement (78.31 ± 1.32 mm) than the BEHIND EAR placement (111.86 ± 3.22 mm). Effective angle was greater (P < 0.0001) for the FRONTAL placement (4.72 ± 0.20°) than the BEHIND EAR placement (3.22 ± 0.17°). Type of PCB did not impact tissue thicknesses, so PCB types were pooled for each placement. Soft tissue thickness was less (P < 0.0001) in the FRONTAL placement (7.83 ± 0.29 mm) than the BEHIND EAR placement (56.01 ± 3.25 mm). Cranial thickness was greater (P < 0.0001) in the FRONTAL placement (48.49 ± 1.81 mm) than the BEHIND EAR placement (39.51 ± 2.49 mm). Total tissue thickness was less (P < 0.0001) in the FRONTAL placement (56.31 ± 1.76 mm) than the BEHIND EAR placement (95.52 ± 3.30 mm). Overall, the data suggest that the FRONTAL placement may have a greater likelihood for successful euthanasia of sows >200 kg BW due to the lesser distance to the thalamus and total tissue thickness, as well as larger effective angle.