Evaluation of brain damage resulting from penetrating and non-penetrating captive bolt stunning using lambs

Objective To compare the brain damage in sheep resulting from penetrating a nd non-penetrating captive bolt stunning. Design The unrestrained heads of anaesthetised lambs were impacted in the t emporal region with penetrating and non-penetrating captive bolt pistols (h umane stunners) using a constant charge. Two hours after head impact, brain s were perfusion-fixed with 4% paraformaldehyde. Coronal sections were stai ned with haematoxylin and eosin and immunohistochemically for amyloid precu rsor protein, a sensitive marker of axonal and neuronal reaction in brains after trauma. Pathological changes in these brains were then quantified by morphometric analysis. Results The skull was fractured in 50% of lambs after a non-penetrating hea d impact and in all animals after a penetrating head wound. Impact contusio ns were present in 80% of lambs receiving a non-penetrating head injury and in all of those with a penetrating wound. Total contusion area was similar in both groups. Amyloid precursor protein-positive axons and neurons, and haemorrhage, were widely distributed in the brain after both head impact ty pes, but there was no statistically significant difference between the two groups. Multifocal necrosis of the cerebellar granular layer was found in a ll lambs with non-penetrating head injury, but in none with a penetrating i njury. Conclusions The structural brain damage, a mixture of focal and diffuse inj ury, produced by penetrating and nonpenetrating captive bolt pistols was ov erall similar and of sufficient severity to suggest that both types of weap on are acceptable for euthanasia.