Validating the effectiveness of alternative euthanasia techniques using penetrating captive bolt guns in mature swine (Sus scrofa domesticus)

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, and 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 the inclusion criteria described in stage one. 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 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 with the pistol type of the 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 with 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 with 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.     

Anatomical and histologic pathology induced by cervical dislocation following blunt head trauma for on-farm euthanasia of poultry

The selection of an optimal method for on-farm euthanasia of poultry in cases of emergency killing is still under debate. The preferred approach would spare pain and suffering and would ensure proper stunning as well as rapid death. Here, the effects and pathological lesions induced by blunt trauma to the head followed by cervical dislocation were studied in chickens and turkeys of different weight groups of up to 20 kg. To allow for feasible on-farm execution, including birds heavier than 3 kg, a percussive blow to the head with subsequent manual or mechanical cervical dislocation using a nonpenetrating forceps was employed. Systematic macroscopic, radiographic, and histopathologic examinations were performed with special attention to anatomical structures essential for consciousness and vital functions. The 2 traumatic impacts resulted not only in massive subdural hematomas, cortical brain damage, dissecting vertebral bone fractures, and a disruption of the cervical spinal cord, but also severe lacerations of the medulla oblongata area of the brain stem. The lesions were suggestive of immediate loss of consciousness and indicative of immediate and irreversible loss of central regulation of breathing and heart function. Moreover, the results were largely independent of the weight class examined, indicating that from a pathology perspective the methods used may be suitable for humane euthanasia of poultry of up to 20 kg in live weight.