There has been limited published research on the use of penetrative or non- penetrating captive bolt for euthanasia of swine. The CASH Dispatch Kit is a heavy duty cartridge propelled captive bolt device with interchangeable muzzle assemblies. The unit provides a non-penetrating captive bolt muzzle for piglets, and a variety of penetrating bolt assemblies for pigs ranging from large nursery-age pigs to mature breeding stock. The overall objective of this project was to determine effectiveness of a single application of the captive bolt device for euthanasia of pigs at different ages.
The first experiment explored effectiveness of the Cash Dispatch captive bolt device when applied to anesthetized pigs in a controlled laboratory setting, and also to evaluate the association between traumatic brain injury to anatomical regions of the brain and effectiveness of captive bolt technology for euthanasia of pigs at different ages. Forty two pigs, six from each of 7 weight classes (2-3kg, 7.5-10 kg, 15-20 kg, 30-40 kg, 100-120 kg, 200-250 kg, >300 kg) were enrolled. Each pig was anesthetized, and then euthanized with the “Cash” Dispatch Kit. Death was determined according to time to last heartbeat and respiratory function. Postmortem dissection was used to determine the presence of hemorrhaging and the extent of traumatic brain injury. All 30 pigs in the 5 lightest weight classes were effectively euthanized. Four of the 12 pigs in the heaviest weight classes required a secondary method. For pigs that were successfully euthanized with a single shot, movement typically ceased within 1 to 2 minutes. However, there was tremendous variability in this response, and casual observation indicated that many pigs displayed repeated bouts of involuntary movement and quiescence. Heartbeat typically ceased after approximately 4 minutes, taking approximately twice a long to cease when compared to last movement. Weight class associated with time to last heartbeat (p=0.0071), such that the duration of heartbeat decreased by 26 seconds for each increase in weight class.
All pigs that were successfully euthanized with a single application of the CASH Dispatch captive bolt device displayed haemorrhage in all 5 neuroanatomical regions assessed (cerebral cortex, cerebellum, thalamus, pons and medulla). However, 2 of the 4 pigs requiring a secondary euthanasia step lacked haemorrhage in the medulla and pons. Interestingly, although all pigs successfully euthanized with a single shot of the penetrating captive bolt displayed traumatic brain injury in the cerebral cortex, only 1 pig (weight class 4) showed traumatic brain injury in any of the other 4 regions of the brain.
In the second experiment, the effectiveness was assessed when the Cash Dispatch captive bolt device was used by stockpeople on commercial farms. Two hundred and ten pigs in the same 7 weight classes were enrolled in the trial. Fifteen stockpersons were enlisted from a single production company to perform euthanasia. There were 202 pigs (97%) that were effectively euthanized with a single application of the “Cash” Dispatch Kit. Seven pigs (2 sows and 5 boars) in the heaviest weight classes required a second shot. Weight class was significantly associated with the need for a second shot (P=0.006). Stockperson was also associated with the need for a second shot (p=0.0048), but there were no differences between sows and boars. Two-thirds of the pigs that required a second shot vocalized (p=0.0038). Similarly, two-thirds of pigs that required a second shot displayed respiration after the initial shot (p=0.00002). However, vocalization and respiration were also observed in pigs that were successfully euthanized, indicating that neither is a reliable predictor of euthanasia success.
Based on expected slaughter standards published by the American Meat Institute (AMI, 2010), insensibility must be achieved 95% of the time when using a captive bolt gun in order to obtain a passing score on the animal welfare audit. In Experiment 1, the Cash Dispatch Kit successfully euthanized 100% of the anesthetized pigs in the 5 lowest weight classes with a single application. However, 8 of the 12 (66%) pigs in the mature weight classes (200+ kg) required a secondary method. The manufacturers adjusted the device following the results from Experiment 1, in terms of increasing the cartridges for mature animals, and decreasing the charge for the smallest weight class. In Experiment 2, 97% of all pigs were successfully euthanized with a single application of the modified Cash Dispatch device, and again variability occurred in the mature weight classes (>200kg) in which 10% of the animals required a second shot. In the on-farm study, application of a second shot was sufficient to ensure euthanasia, and can be an alternative to exsanguination (bleeding) or pithing.
There were associations between stockperson and a number of outcome variables, including the need for a second shot. However, stockperson was confounded with weight class, since individuals worked in particular stages of production, and hence further research is needed to clearly understand this factor. Our casual observation suggests that landmarks on the pig head were usually correctly identified, but ensuring that the pistol was flush against the head at a correct angle was likely to affect efficacy. Restraint of the head through snaring appeared to be important for both efficacy and safety, rather than restraint in a chute or stall.
We conclude that the Cash Dispatch captive bolt device is effective as a single step euthanasia method for pigs <200kg. For mature animals, further refinements in terms of equipment design and/or application by stockpeople are needed to ensure reliable performance with mature animals. Stockpeople should be prepared to administer a second shot swiftly when euthanizing mature pigs with a captive bolt device.
