Investigating tissue depth parameters of cadaver heads from market and mature swine in relationship to penetrating captive bolt euthanasia
2021-12
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Investigating tissue depth parameters of cadaver heads from market and mature swine in relationship to penetrating captive bolt euthanasia
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2021-12
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The definition of animal welfare includes how an animal dies. As such, ensuring a good death through effective, safe, and validated euthanasia practices is a critical piece of promoting positive animal welfare. The overall objective of this thesis was to provide a baseline understanding of tissue depth parameters associated with the euthanasia of mature swine with a penetrating captive bolt (PCB) using cadaver heads as a model. The first chapter provides a review of the literature regarding the captive bolt euthanasia of swine. Specifically, this highlights the challenges associated with the use of PCB as method of euthanasia for mature sows and boars. Penetrating captive bolt is a method of euthanasia that is approved for use with mature swine with a common frontal placement across euthanasia guidelines; however, the method has not been scientifically validated as an effective method of euthanasia for these animals.
The second chapter focuses on the impact of cooling on the soft tissue thickness, cranial thickness, total tissue thickness, and cross-sectional brain area of cadaver heads from market pigs following the application of a PCB shot to the common frontal location. Cadaver heads were obtained from 36 market hogs that were commercially slaughtered (CO¬¬¬2 stunned) and each head received a PCB application in a frontal placement that was 2.54 cm above the optic orbits at the midline. Following this PCB application, each head was split along the bolt path and subsequently received an UNCHILLED treatment which was followed by a CHILLED treatment. The UNCHILLED treatment involved imaging immediately following the PCB application and head splitting; the CHILLED treatment involved the repeat imaging of the same heads after storage in a walk-in cooler at 2-4° C for 24 h. Measurements of soft tissue thickness differed between CHILLED and UNCHILLED heads, both caudally and rostrally to the bolt path (P = 0.0120 and P = 0.0378, respectively). A correction factor of 1.12 was determined to be necessary in order to estimate UNCHILLED soft tissue thickness from CHILLED soft tissue thickness. However, there was no evidence to support a difference in measurements of cranial thickness, total tissue thickness, or cross-sectional brain area between CHILLED and UNCHILLED heads.
The objectives of the third chapter were (a) to determine the tissue depth, cross-sectional brain area, regions of brain damage (BD), overall BD, and bolt-brain contact associated with the frontal, temporal, and behind ear shot placements for the euthanasia of swine via PCB on sow and boar cadaver heads, and (b) to determine the relationship between external dimensional head measurements and tissue depth, cross-sectional brain area, regions of BD, and bolt-brain contact associated with the frontal, temporal, and behind ear PCB placements. Three PCB placements were evaluated: FRONTAL – 3.5 cm superior to the optic orbits at midline, TEMPORAL – at the depression posterior to the lateral canthus of the eye within the plane between the lateral canthus and the base of the ear, and BEHIND EAR – directly caudal to the pinna of the ear on the same plane as the eyes and targeting the middle of the opposite eye. For sows, the bolt path was in the plane of the brain for 42/42 (100%) FRONTAL heads, 39/40 (97.5%) TEMPORAL heads, and 34/39 (87.5%) BEHIND EAR heads. Brain damage was detected in 25/26 (96.2%) FRONTAL heads, 24/35 (68.6%) TEMPORAL heads, and 5/40 (12.5%) BEHIND EAR heads. For boars, the bolt path was within the plane of the brain for 17/17 (100%) FRONTAL heads, 18/18 (100%) TEMPORAL heads, and 14/14 (100%) BEHIND EAR heads. Brain damage was detected in 11/12 (91.7%) FRONTAL heads, 2/15 (13.3%) TEMPORAL heads, and 7/14 (50.0%) BEHIND EAR heads. For both sows and boars, total tissue thickness was greatest (P < 0.05) for the BEHIND EAR placement (89.3 ± 1.5 mm and 90.9 ± 3.5 mm, respectively) and least (P < 0.005) for the FRONTAL placement (52.7 ± 1.0 mm and 41.2 ± 2.1 mm, respectively). The data in this study indicated that the FRONTAL placement may have the greatest likelihood for successful euthanasia of swine greater than 200 kg body weight (BW) due to the least total tissue thickness and high prevalence of brain damage and may present less risk of failure than the alternative TEMPORAL or BEHIND EAR placements.
The work presented in this thesis highlights the need for the development of PCB devices that have the capacity to reach the brain in mature sows and boars, as well as the need for the adoption of a stepwise approach in future investigations of PCB euthanasia for mature sows and boars.
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University of Minnesota M.S. thesis. December 2021. Major: Veterinary Medicine. Advisor: Perle Zhitnitskiy. 1 computer file (PDF); xvi, 122 pages.
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Anderson, Karly. (2021). Investigating tissue depth parameters of cadaver heads from market and mature swine in relationship to penetrating captive bolt euthanasia. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/252491.
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