Abstract
Penetrating captive bolt (PCB) is widely used for stunning and on-farm dispatch of livestock, yet its efficacy can vary, with the potential for animal welfare compromise. This study investigated the pathophysiology of PCB-induced trauma in horned and polled sheep (Ovis aries), focusing on factors contributing to incomplete concussion. Thirty-seven (n = 18 horned Scottish blackface and n = 19 polled North Country mule) mature ewes (aged 4-10 years) were shot with PCB with varying cartridge power and PCB modifications, followed by clinical assessment and post-mortem analysis using magnetic resonance imagining (MRI) and gross pathology. The results indicated that damage to the reticular activating system, bolt velocity and penetration depth are crucial for inducing irreversible unconsciousness, with depths less than 37 mm often resulting in incomplete concussion. MRI provided detailed insights into brain injuries, aligning well with gross pathological findings. This study highlights the importance of precise bolt placement and appropriate PCB configurations in ensuring humane outcomes, with MRI proving to be a valuable tool for assessing brain trauma in stunned animals. These findings enhance the understanding of effective stunning techniques and support improved welfare practices in livestock management.