No abstract

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.

Electrocution and use of a penetrating captive bolt gun (PCBG) are both acceptable methods of euthanasia for market weight swine. Research has demonstrated that a PCBG is effective in both growing and mature swine. Given limited to no published research base on electrocution in mature swine, the objectives of the present study were to evaluate the efficacy of a two-stage (head-only followed by head-to-heart, 10 s contact for each) mobile electric stunner (E-STUN, Hubert HAAS TBG 96N) and to assess euthanasia outcomes when comparing E-STUN with frontal placement of a heavy duty PCBG (Jarvis, In-line Cylinder Style) when applied to heavy weight (>200 kg), mature boars and sows. Effectiveness of the E-STUN and PCBG were evaluated first in unconscious anesthetized mature swine (n = 7 boars and sows per treatment; average weight 282 ± 48 kg, n=28) to reduce the risk of failure in a conscious animal and then in conscious mature swine (n = 3 boars and sows per treatment; average weight 282 ± 63 kg, n=12). Data from both stages were combined for analyses. Treatment efficacy was defined as any pig that achieved cardiac and respiratory arrest within 10 min after treatment application. A three-point traumatic brain injury (TBI) score (0 = normal; 1 = some abnormalities; 2 = grossly abnormal, unrecognizable) was used to evaluate six neuroanatomical structures (cerebral cortex, cerebellum, hypothalamus, thalamus, pons, and brain stem), and the presence of intracranial hemorrhage was also noted. All animals were immediately rendered insensible with E-STUN and PCBG and no difference was noted between treatments for detection of corneal reflex following treatment application (P = 0.11). Rhythmic breathing was absent following administration of either E-STUN or PCBG. When evaluating time to last heartbeat, there was a significant interaction between sex and treatment. Boars euthanized via E-STUN had 346.8 s decrease in time to last heartbeat compared to boars euthanized via PCBG (P < 0.001) and females euthanized via E-STUN had a 479.3 s decrease in time to last heartbeat compared to females euthanized via PCBG (P < 0.001). Intracranial hemorrhage was common for both methods and visible disruption of neural tissue was evident due to the physical nature of the PCBG. This study demonstrated that a mobile E-STUN system is as effective as a heavy duty PCBG in inducing insensibility and death and shows promise as an alternative method for euthanizing mature pigs on-farm.