Resource

This poster was presented at the 2017 EDEN Annual Meeting in Moline, IL.

ABSTRACT:

Currently, the only single-step methods of euthanasia approved for use in cattle are gunshot or barbiturate overdose, both of which are impractical for mass depopulation scenarios. Penetrating captive bolt (PCB) is a third option; however, death is not assured by the use of PCB alone. For this reason, the AVMA Euthanasia Guidelines recommend the use of a secondary or adjunctive step to assure death whenever PCB is used. In the event of a national livestock health emergency requiring the mass depopulation of thousands of cattle in a large feedlot or dairy, a method that will assure the efficient and humane death of animals is needed. One of the methods proposed by USDA-APHIS is a pneumatically powered penetrating captive bolt with low-pressure air channel pithing through the bolt (AP-PCB). This device was
specifically designed to cause sufficient brain damage to alleviate the need for a secondary step to assure death. Unlike the PCB used in packing plants which penetrate only about 3-3 ¼ inches into the brain, the bolt of the AP-PCB penetrates
5.5 to 6 inches deep. This increases its potential to make contact with deeper structures within the brain, such as those that make up the brain stem (thalamus, hypothalamus, midbrain, pons, and medulla oblongata). A study to validate this
device proved the AP-PCB to be highly effective as a single-step method (i.e. not requiring a secondary method to assure death) for the euthanasia of cattle. When accurately placed over the correct anatomical site, use of this device alone
caused an immediate loss of consciousness followed by death in all (n = 66) animals studied. Mean time to death following use of the AP-PCB was an average of 7.3 minutes post shot. Brain trauma was assessed by 1) a subjective estimate of the amount of physical damage to the brain, 2) by a visual estimation of the degree of hemorrhage within the cranial vault, and 3) by totaling the number and location of bone fragments in various regions of the brain in study animals. The percent of animals with significant brain damage by region was the cerebrum 100%, thalamus and hypothalamus 76%, midbrain 53%, pons 27%, cerebellum 21% and medulla oblongata 17%. Blood that escapes into the subarachnoid space and cerebrospinal fluid causes pressure on the brain which alone is life threatening. Hemorrhage
was scored using severity scores 0-3 with 0 being no hemorrhage and 3 being severe hemorrhage. Most hemorrhage was observed on the ventral surface of brainstem tissues. Using this scoring system the midbrain, pons, medulla oblongata, spinal cord and thalamus/hypothalamus were judged to have a hemorrhage severity score of 3. The more dorsal regions of the brain including the cerebellum and cerebrum had lower hemorrhage scores. Fragments of bone exacerbate brain trauma as they are driven deeply into the brain by the penetrating bolt. Bone fragments were observed
in 92% of the cerebrums,18% of midbrains, 17% of thalamus and hypothalamuses, 9% of cerebellums, 3% of medulla oblongata(s), 2% of pons(s), and 2% of the spinal cords in central nervous system tissues examined. Damage to the brain also occurs from concussion and the increase in intracranial pressure associated with the bolt entering the brain. The importance of low-pressure air-injection (approximately 15 psi.) through the bolt with the AP-PCB to increase brain trauma is unclear. This question prompted the follow-up study reported here which was intended to validate effectiveness of the Jarvis USSS-3 pneumatically powered penetrating captive bolt equipped with a “non-air pithing bolt” (Non-AP-PCB) as a single-step method for humane euthanasia of cattle. As in the original study of the AP-PCB, clinical parameters associated with unconsciousness, brain trauma and time to death were monitored. Results of our studies of the Non-AP-PCB confirm that it is also very lethal and in no case was a secondary step to assure death required. Based on our observations of clinical parameters and brain trauma scoring we conclude that the Jarvis USSS-3 Pneumatic Stunner equipped with either the AP-PCB and Non-AP-PCB is an effective tool for mass depopulation of cattle.