Brain damage in sheep from penetrating captive bolt stunning

Abstract

ObjectiveTo determine the severity and distribution of structural changes in the brains of adult sheep stunned by penetrating captive bolt.Procedure The unconstrained heads of ten, anaesthetised, unhorned, 2-year-old Merino sheep were impacted at the summit of the head with a penetrating captive bolt pistol. Six sheep were ventilated and four received no respiratory support. Two hours after impact, brains from the six ventilated sheep were perfusion-fixed with 4% paraformaldehyde. Sixteen whole, serial coronal sections from each brain were stained with haematoxylin and eosin and immunohistochemically for amyloid precursor protein, a sensitive marker of axonal and neuronal reaction in the brain after trauma. Pathological changes in these brains were then quantified by morphometric analysis. ResultsStructural change in all impacted brains was a mixture of focal injury around the wound track and more widely distributed damage in the cerebral hemispheres, cerebellum and brainstem, but varied considerably in severity between individual sheep. All nonventilated sheep died rapidly following respiratory arrest. ConclusionsAfter penetrating captive bolt stunning, damage to the central reticular formation, axonal connections, and the cortical mantle is the likely reason for failure of respiratory control and traumatic loss of consciousness. Aust Vet J 2002;80:67-69 APP Amyloid precursor protein A lthough penetrating captive bolt pistols are commonly used for euthanasia of sheep, 1-3 the structural changes in the brain after mechanical stunning have been little studied.The position on the head usually recommended for captive bolt stunning of sheep without horns, and that used in the present study, is the midline at the highest point, aiming straight down toward the angle of the jaw. 1-3 However, in the field, stunning should not be always relied upon to render an animal permanently unconscious and must be followed by an adjunctive method to ensure death. This paper reports the detailed neuropathology resulting from penetrating captive bolt stunning of adult sheep. Materials and methodsSix, 2-year-old, unhorned, Merino ewes were anaesthetised (isoflurane) and ventilated with a mixture of oxygen and nitrogen titrated against regular blood gas measurements to maintain a normal blood gas profile, and the arterial blood pressure and heart rate were monitored. These sheep were placed in the sphinx position with their heads supported to permit free movement after impact at the summit of the head with a penetrating stunner (Karl Schermer & Co, Karlsruhe, Germany), 15 min after induction of anaesthesia. A Schermer No 17 charge was inserted into a chamber behind the proximal end of the bolt to propel the captive bolt from the muzzle of the stunner into the head. Four control sheep were not impacted, but otherwise subjected to the same experimental protocol. Sheep remained anaesthetised until killed by perfusion fixation of the brain Four additional sheep were anaesthetised but not ventilated after impact, mean arterial blood press...

Pathophysiology of penetrating captive bolt stunning in Alpacas (Vicugna pacos)

“…insensibility (Gibson et al, 2012). However, in the current study, the results suggest that for alpacas, CBG injury induces insensibility principally by direct physical trauma (focal and diffuse injury) from the bolt to the structures of the diencephalon and brainstem (Finnie, Manavis, Blumbergs, & Summersides, 2002). Pressure effects, in the form of flattening of the cerebrum contralateral to the CBG shot, were observed.…”

Evaluation of a spring-powered captive bolt gun for killing kangaroo pouch young

“…Properties of the skull and brain of immature animals could also potentially influence the effectiveness of captive bolt stunning. Insensibility from penetrating captive bolt stunning is caused by a combination of direct mechanical damage to the brain (diencephalon and brainstem) by the penetrating bolt and focal and diffuse injuries to the white matter pathways connecting these areas (Finnie et al 2002). Much of this diffuse damage is thought to occur during the biomechanical transfer of kinetic energy from the bolt to head at the time of impact (Shaw 2002).…”

Large animal models of traumatic brain injury

“…Penetrating injury models were first developed in cats (Carey, Sarna, & Farrell, ) and then subsequently applied to sheep (Finnie, Manavis, Blumbergs, & Summersides, ). Designed to mimic missile wound injury to the brain, the model incorporates either firing a missile (bullet or metal sphere) into the brain of a restrained animal or allowing penetration using a captive bolt device (Finnie et al, ), with the energy delivered by the impact titrated down to nonlethal levels. Morphologically, the model produces extensive laceration and crushing of tissue; stretching of blood vessels, neurons, and axons; plus a significant hemorrhagic cavity (Finnie et al, ).…”

“…Designed to mimic missile wound injury to the brain, the model incorporates either firing a missile (bullet or metal sphere) into the brain of a restrained animal or allowing penetration using a captive bolt device (Finnie et al, ), with the energy delivered by the impact titrated down to nonlethal levels. Morphologically, the model produces extensive laceration and crushing of tissue; stretching of blood vessels, neurons, and axons; plus a significant hemorrhagic cavity (Finnie et al, ). The presence of extensive hemorrhage plus the vasogenic edema around the wound track was accompanied by elevations in ICP and decreased cerebral perfusion pressure (Carey et al, ).…”