Euthanasia of mature swine is challenging. Temporal and behind-the-ear locations are two sites that have been identified as alternatives to the more commonly used frontal placement. In stage-one, the effectiveness of two penetrating captive bolt gun styles (cylinder or pistol) was evaluated using frontal, temporal and behind-the-ear placement in anesthetized mature swine (n=36; weight: 267 ± 41 kg). For stage-one, when evaluating treatment efficacy by sex, the cylinder style equipment was 100% effective in achieving death when applied to all cranial locations (frontal, temporal, behind-the-ear) for sows; however, the pistol style equipment was only 100% effective when applied at the behind-the-ear location for sows. For boars, the cylinder style equipment was 100% effective when applied to the frontal and behind-the-ear location, but the pistol style equipment was not effective for any cranial location in boars. Therefore, the pistol-frontal, pistol-temporal, pistol- behind-the-ear and cylinder-temporal were not included for boars, and pistol-frontal and pistol-temporal were not included for sows in stage-two. In stage-two, commercial, mixed breed, mature swine (n=42; weight: 292 +/- 56 kg) were randomly assigned to one of four treatments based on inclusion criteria described in stage-one. A 3-point traumatic brain injury (TBI) score (0=normal; 1=some abnormalities; 3=grossly abnormal, unrecognizable) was used to evaluate six neuroanatomical structures (cerebral cortex, cerebellum, hypothalamus, thalamus, pons and brain stem) and the presence of hemorrhage was also noted. All treatments were 100% effective in stage-two. A significant interaction between gun style and placement was determined on predicting total TBI as the cylinder style produced a higher total TBI score compared to the pistol type, of magnitude of +2.8 (P < 0.01). The cylinder style tended to produce a greater TBI score than the pistol in the temporal location (+1.2; P=0.08). No difference was noted for TBI score behind-the-ear between the cylinder and pistol style gun (P>0.05). TBI tended to be less in boars compared to sows (-0.6; P=0.08). Hemorrhage was observed in frontal, parietal, occipital and temporal lobes. This study demonstrated that the cylinder style captive bolt gun more effectively resulted in brain trauma and death compared to a pistol style gun and the behind-the-ear and temporal placement showed promise as an alternative placement site for euthanizing mature pigs on-farm.
Kramer S, Wagner B, Robles I, Moeller S, Bowman A, Kieffer J, Arruda A, Cressman M, Pairis-Garcia M. Validating the effectiveness of alternative euthanasia techniques using penetrating captive bolt guns in mature swine (Sus scrofa domesticus). J Anim Sci. 2021 Feb. https://doi.org/10.1093/jas/skab052