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Quantification of cooling effects on basic tissue measurements and exposed cross-sectional brain area of cadaver heads from market pigs

Quantification of cooling effects on basic tissue measurements and exposed cross-sectional brain... Quantification of cooling effects on basic tissue measurements and exposed cross- sectional brain area of cadaver heads from market pigs † ‡ || ‡ ‡ Karly N. Anderson, Sarah E. Albers, Kaysie J. Allen, Katherine D. Bishop, Brian J. Greco, ‡ $ ‡ ‡,1 Christina M. Huber, Ashlynn A. Kirk, Hannah Olsen, and Kurt D. Vogel Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, USA; Department of Animal and Food Science, University of Wisconsin–River Falls, || River Falls, WI, USA; Department of Animal and Dairy Sciences, University of Wisconsin–Madison, Madison, WI, USA; and Center for Animal Welfare, Department of Animal Science, University of California–Davis, Davis, CA, USA ABSTRACT: The objective of this project was to the plane of the bolt path immediately prior to determine the impact of cooling on the soft tissue and immediately after the refrigeration treatment. thickness, cranial thickness, and cross-sectional Measurements were performed by two observers. brain area of cadaver heads from market pigs. Across all measurements, mean interobserver coef- Documenting the effect of cooling on tissue dimen- ficient of variation was 11.3 ± 0.6%. The soft tissue sions of swine heads is valuable and important for caudal to the bolt path was different (P = 0.0120) future investigations of physical stunning and eu- between treatments (CHILLED: 6.4  ± 0.2  mm; thanasia methods that use cadaver heads. Scalded UNCHILLED: 7.2  ± 0.2  mm). The soft tissue and dehaired cadaver heads with intact jowls were thickness rostral to the bolt path was different sourced from market pigs stunned with CO gas. (P  =  0.0378) between treatments (CHILLED: After transport to the data collection location, a 5.5  ± 0.2  mm; UNCHILLED: 6.1  ± 0.2  mm). penetrating captive bolt (PCB) shot (Jarvis Model Cranial thickness caudal to the bolt path was not PAS—Type P 0.25R Caliber Captive Bolt Pistol different (P = 0.8659; CHILLED: 18.1 ± 0.6 mm; with Medium Rod Assembly and Blue Powder UNCHILLED: 18.3 ± 0.6 mm), nor was there a Cartridges) was applied in the frontal position. significant difference (P = 0.2593) in cranial thick- Following PCB application, each head (n  =  36) ness rostral to the bolt path between treatments underwent an UNCHILLED treatment followed (CHILLED: 16.2  ± 0.6  mm; UNCHILLED: by CHILLED treatment. The UNCHILLED 15.2 ± 0.6 mm). Cross-sectional brain area did not treatment involved images collected immediately differ (P = 0.0737; CHILLED: 3633.4 ± 44.1 mm; after splitting each head along the bolt path, and UNCHILLED: 3519.9 ± 44.1 mm). A correction the CHILLED treatment involved images of the factor of 1.12 was determined from this study for same heads after storage in a walk-in cooler for cases where estimation of UNCHILLED soft 24 h at 2 to 4°C. All measurements for each treat- tissue thickness from CHILLED soft tissue thick- ment were collected from images of the heads on ness is necessary. Keywords: captive bolt, euthanasia, slaughter, stunning, swine © The Author(s) 2021. Published by Oxford University Press on behalf of the American Society of Animal Science. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribu- tion, and reproduction in any medium, provided the original work is properly cited. Transl. Anim. Sci. 2021.5:1-6 doi: 10.1093/tas/txab001 Corresponding author: kurt.vogel@uwrf.edu Received November 15, 2020. Accepted January 6, 2021. 1 Anderson et al. INTRODUCTION by the United States Department of Agriculture Food Safety and Inspection Service (USDA FSIS) Penetrating captive bolt (PCB) is a method of in accordance with the regulations in 9 CFR 313. euthanasia and stunning approved for a variety The heads used in this study were acquired as meat of livestock species by the American Veterinary products that were suitable for human consump- Medical Association (AVMA 2016, 2020), the tion. The exemption from IACUC approval fol- National Pork Board (NPB) and American lowed the precedent established by Anderson et al. Association of Swine Veterinarians (AASV) for (2019). swine (NPB, 2016), and the American Association of Bovine Practitioners (AABP, 2019) for cattle. Description of Cadaver Heads There has been growing interest in assessing the implications of bolt length used with cattle Thirty-six heads, scalded and dehaired with (Kline et al., 2019; Wagner et al., 2019), physical skin on and jowls intact, were obtained from pigs landmarks for PCB placement for cattle (Gilliam that were commercially slaughtered at a regional et  al., 2012, 2016, 2018), and alternative PCB processing facility under federal inspection. The placement in swine (Anderson et  al., 2019). The heads were inspected and passed for human con- brain is a semifluid structure that makes the as- sumption. The estimated body weight (BW) of the sessment of brain damage attributed to the PCB pigs was 136 kg, and they were approximately 6 mo itself difficult due to tissue distortion during the of age. Exact BW and age of each pig was not avail- head splitting process (Kline et al., 2019). At the able, so estimates of age and weight were based on time of our study, there did not appear to be any the purchasing specifications of the establishment. published data to quantify the impact of cooling Each head was removed from its respective car- on the tissue parameters of cadaver heads of any cass via knife incision between the atlas and axis by species following the application of a captive plant personnel. All heads were packaged in plastic bolt. Understanding and accounting for poten- bags and boxed prior to unrefrigerated transport tial changes in tissue dimensions associated with (distance traveled: 180 km) to the University of cooling are important for future investigations Wisconsin—River Falls Meat Science Laboratory related to the captive bolt stunning and euthan- where the project commenced within approximately asia of livestock species, as chilling allows for a 6 h of head collection. greater degree of accuracy when assessing brain damage because the bolt path remains clearly vis- Description of Captive Bolt Tool and Placement ible in cooled brain tissue. The objective of this study was to quantify The PCB device used in this study was the impact of cooling on the soft tissue thick- a Jarvis Model PAS—Type P 0.25R Caliber ness, cranial thickness, total tissue thickness, and Captive Bolt Pistol (order no.  4144035, Jarvis cross-sectional brain area of cadaver heads from Corp., Middletown, CT) equipped with market pigs following the application of a PCB Medium Stunning Rod Nosepiece Assembly shot to the common frontal location. Our hy- (order no.  3116604, Jarvis Corp.). Jarvis Blue pothesis was that UNCHILLED cadaver heads Powder Cartridges—0.25R Caliber, 3GR (order would display soft tissue thickness, cranial thick- no.  1176018, Jarvis Corp.) were utilized for all ness, total tissue thickness, and cross-sectional PCB applications in this study. All equipment brain area that was not different than CHILLED and placement procedures were the same as used cadaver heads. by Anderson et al. (2019). The PCB was placed in the frontal location as described by Woods et al. MATERIALS AND METHODS (2010) at 2.54 cm superior to a line drawn across the top of the eyes at the midline. To ensure con- Animal Use Protocol sistent placement and entry angle of the PCB, the It was not necessary to submit an animal use barrel of the captive bolt pistol was fitted with a protocol to the University of Wisconsin—River custom-fabricated flange. The flange maintained Falls Institutional Animal Care and Use Committee a perpendicular relationship between the PCB (IACUC) because live animals were not directly and frontal plate of the cranium. To prevent the manipulated in this study. The pigs from which the movement during PCB application, each head heads were obtained were slaughtered at a com- was placed on a solid surface and held firmly in mercial slaughter establishment under inspection place by the snout and the ears. Translate basic science to industry innovation Quantification of cooling effects Postapplication Head Processing cranium along the bolt path. This measurement was reported caudal and rostral to the bolt path. Total Following the application of the shot location tissue thickness (mm), which referred to the total treatment, each head was cut along the bolt path soft tissue and cranial thickness from the site of ap- with a meat band saw. Following each cut, digital plication to the interior surface of the cranium, was images were collected from both the left and right determined from the summation of the soft tissue sides of each exposed intracranial surface. Thermal and cranial thicknesses for each cadaver head. This images (Model E8, FLIR Systems, Boston, MA) measurement was reported caudal and rostral to were also collected from both the left and right the bolt path. Soft tissue thickness, cranial thick- sides of each exposed intracranial surface for tem- ness, and total tissue thickness were determined perature assessment. All images were collected by averaging the measurements from the right and with the thermal camera and digital camera posi- left halves each head for the rostral aspect and the tioned 54.6  cm directly above and perpendicular caudal aspect of the bolt path. Cross-sectional to the exposed cut surface. Following image collec- brain area (mm ) referred to the cross-sectional sur- tion, the two halves of each head were reassembled face area of the exposed brain area within the plane and wrapped with polyvinylchloride film prior to of the bolt travel as described by Anderson et  al. chilling for 24 h at 2 to 4°C. (2019). Measurements of cross-sectional brain area were calculated from both the right and left halves Thermal Image Collection and Analysis along the paths of bolt travel and averaged prior to statistical analysis. All measurements were repeated Temperature data were collected with a thermal 24 h after each head was placed under refrigeration. imaging camera (FLIR E8, FLIR Systems). The accuracy of temperature emission readings for this Statistical Analyses model was ±2°C or ±2% of reading, for ambient temperature 10 to 35°C and object temperature All continuous data for captive bolt applica- above 0°C. The camera also utilized Multi-Spectral tion treatment (UNCHILLED, CHILLED) effects Dynamic Imaging to enhance the thermal image were analyzed using models constructed within the with a visible camera detail based on a simultan- MIXED procedure of SAS (Statistical Analysis eously collected digital image. Thermal images System Institute, Inc., Cary, NC) with Kenward– were uploaded to a laptop computer and viewed on Roger denominator degrees of freedom designated FLIR Tools software (FLIR Systems) to determine within each model and mean separation performed maximum intracranial temperature. All digital im- with the Tukey’s test designation. For all ana- ages were also uploaded to a laptop computer for lyses, the experimental unit was individual head. tissue and area measurement collection. Significant differences in treatment effects were rec- ognized at α ≤ 0.05. Tissue and Cranial Measurements RESULTS AND DISCUSSION Measurements of soft tissue thickness (mm), cranial thickness (mm), and cross-sectional brain Tissue measurements, cross-sectional brain area (mm ; Figure  1) were determined from im- areas, weights, and temperatures collected from ages collected at the time of head processing for the this study can be observed in Table  1. Soft tissue control heads and 24  h after head processing for thickness was significantly different (P < 0.05) be- chilled heads. All images included a 15.0-cm ruler tween the UNCHILLED and CHILLED treat- that was used as a reference for an online irregular ments. There were no significant differences area calculator (SketchandCalc, iCalc, Inc., Palm (P > 0.05) in cranial thickness, total tissue thick- Coast, FL). All measurements were performed by ness, and cross-sectional brain area between the two trained observers. Across all measurements, the UNCHILLED and CHILLED treatments. Head mean interobserver percent coefficient of variation weight was not significantly different (P > 0.05) was 11.3  ± 0.6%. Soft tissue thickness referred to between the UNCHILLED and CHILLED treat- the tissue from the application site to the exterior ments. Cranial temperature was significantly dif- surface of the cranium. This measurement was re- ferent (P < 0.05) between the UNCHILLED and ported caudal and rostral to the bolt path. Cranial CHILLED treatments. thickness referred to the thickness from the exterior Soft tissue thickness caudal to the bolt path was surface of the cranium to the interior surface of the greater (P = 0.0120) in UNCHILLED heads (7.2 ± Translate basic science to industry innovation Anderson et al. Figure 1. Soft tissue thickness—the tissue from the application site to the exterior surface of the cranium along the bolt path; cranial thickness—the thickness from the exterior surface of the cranium to the interior surface of the cranium along the bolt path; brain area—the cross-sectional surface area of the exposed brain area within the plane of the bolt travel. Soft tissue thickness and cranial thickness were meas- ured at the rostral and caudal aspects of the bolt path on the right and left halves of each split head. Values were averaged prior to statistical analysis. Table 1.  Effects of cooling on tissue parameters and cross-sectional brain area of cadaver heads from market weight hogs assigned to an UNCHILLED and CHILLED treatment and sectioned by band saw following the plane of bolt travel (n = 36) Refrigeration treatment UNCHILLED CHILLED Dependent variable SEM n SEM n Pooled SE P-value Soft tissue thickness caudal to bolt path, mm 7.2 36 6.4 36 0.2 0.0120 Soft tissue thickness rostral to bolt path, mm 6.1 36 5.5 36 0.2 0.0378 Cranial thickness caudal to bolt path, mm 18.3 35 18.1 36 0.6 0.8659 Cranial thickness rostral to bolt path, mm 15.2 36 16.2 36 0.6 0.2593 Total tissue thickness caudal to bolt path, mm 24.5 35 24.5 36 0.6 0.2577 Total tissue thickness rostral to bolt path, mm 21.3 36 21.7 36 0.7 0.6730 Cross-sectional brain area, mm 3519.9 30 3633.4 31 44.1 0.0737 Head weight, kg 5.8 36 5.6 36 0.1 0.1824 Exposed head temperature, °C 30.6 36 2.7 36 0.1 <0.0001 Refrigeration treatment: UNCHILLED—Data from images collected immediately after captive bolt application; CHILLED—data from im- ages collected 24 h after captive bolt application and refrigeration at 2 to 4°C. Translate basic science to industry innovation Quantification of cooling effects 0.2  mm) than CHILLED heads (6.4  ± 0.2  mm). heads for use in future investigations. The following Soft tissue thickness rostral to the bolt path was formula was used as follows: (UNCHILLED soft also greater (P  =  0.0378) in UNCHILLED heads tissue thickness/CHILLED soft tissue thickness). (6.1  ± 0.1  mm) than CHILLED heads (5.5  ± The caudal and rostral soft tissue thicknesses were 0.2 mm). Cranial thickness caudal to the bolt path averaged for each head within each treatment group was not different (P  =  0.8659) in UNCHILLED prior to calculation of the correction factor. (18.3  ± 0.6  mm) heads than CHILLED (18.1  ± 0.6  mm) heads, nor was cranial thickness ros- IMPLICATIONS tral to the bolt path different (P  =  0.2593) be- As a result of the greater soft tissue thickness tween treatments (UNCHILLED: 15.2 ± 0.6 mm; in UNCHILLED heads compared to CHILLED CHILLED: 16.2 ± 0.6 mm). Total tissue thickness heads, a correction factor of 1.12 was determined caudal to the bolt path did not differ (P = 0.2577) for the prediction of UNCHILLED soft tissue between UNCHILLED (24.5 ± 0.6 mm) heads and thickness from CHILLED soft tissue thickness. Our CHILLED heads (24.5  ± 0.6  mm). Total tissue results did not identify a need for a correction factor thickness rostral to the bolt path was also not dif- when determining UNCHILLED cranial thickness, ferent (P = 0.6730) between UNCHILLED (21.3 ± total tissue thickness, or cross-sectional brain area 0.7  mm) heads and CHILLED (21.7  ± 0.7  mm) from CHILLED heads. It is important to observe heads. There was no difference (P  =  0.0737) differences in tissue damage in future investigations in exposed cross-sectional brain area between of cooling effects on cadaver swine heads as this UNCHILLED (3519.9  ± 44.1  mm ) heads and study was solely focused on detecting differences in CHILLED (3633.4 ± 44.1 mm ) heads. Cranial tem- tissue dimensions. Ultimately, the documentation of perature was greater (P ˂ 0.0001) in UNCHILLED the effect of cooling on tissue dimensions of swine (30.6  ± 0.1°C) heads than CHILLED (2.7  ± heads is valuable and important for future investiga- 0.1°C) heads. tions of physical stunning and euthanasia methods In an assessment of physical landmarks for that use cadaver heads as a model. the PCB euthanasia of cattle, Gilliam et al. (2012) concluded that the variable freezing time and 36-h thaw time may have resulted in the failure of trau- ACKNOWLEDGMENTS matic brain injury scores, although the method The authors thank the commercial slaughter they used had been validated in heads from ani- establishment that provided the cadaver heads for mals that were recently shot with a PCB or bullet this research and the data collection assistance of and not frozen. Gilliam et al. (2016) reported that J.  Bignell and K.  Heussner. The provision of cap- that brain tissue was softened from freezing and tive bolt stunning equipment by Jarvis Corporation thawing cadaver bovine heads, which resulted in and technical support by Bunzl Processor division the tissue collapsing into the bolt path before CT was greatly appreciated. This project was funded by scans of the head, which may have contributed a grant from the University of Wisconsin - River to the observation of shallow penetration depth Falls Undergraduate Research, Scholarly, and from computerized tomography (CT) scans of Creative Activity Program. heads from mature bulls. Conflict of interest statement. None declared. Kline et al. (2019) reported challenges in the as- sessment of damage to brain tissue following the PCB stunning of cattle, due to the gelatinous na- LITERATURE CITED ture of the brain, and recommended a 12- to 24-h AABP. 2019. Guidelines for the humane euthanasia of chill time prior to splitting skulls in future studies cattle. https://aabp.org/Resources/AABP_Guidelines/ for more accurate assessment of brain damage. In EUTHANASIA-2019.pdf (Accessed 6 September 2020). a related study, cattle heads were collected from a Anderson,  K., E.  Ries, J.  Backes, K.  Bishop, M.  Boll, processing plant and chilled at 0°C for 24 h prior to E. Brantner, B. Hinrichs, A. Kirk, H. Olsen, B. Risius, et al. the assessment of damage to specific regions of the 2019. Relationship of captive bolt stunning location with basic tissue measurements and exposed cross-sectional brain and challenges with the assessment of brain brain area in cadaver heads from market pigs. Transl. damage were not noted (Wagner et al., 2019). Anim. Sci. 3:1405–1409. doi:10.1093/tas/txz097 The results in our study were used to calculate a A VMA. 2016. A VMA guidelines for the humane slaughter of ani- correction factor that could be used to estimate the mals: 2016 Edition. https://www.avma.org/KB/Resources/ unchilled soft tissue thickness of market pig heads at Reference/AnimalWelfare/Documents/Humane-Slaughter- Guidelines.pdf (Accessed 5 March 2019). the frontal PCB site from measurements of chilled Translate basic science to industry innovation Anderson et al. AVMA. 2020. AVMA guidelines for the euthanasia of ani- cattle of various ages. Anim. Welf. 27:225–233. mals: 2020 Edition. https://www.avma.org/sites/de- doi:10.7120/09627286.27.3.225 fault/files/2020-01/2020-Euthanasia-Final-1-17-20.pdf Kline,  H.  C., D.  R.  Wagner, L.  N.  Edwards-Callaway, (Accessed 9 April 2020). L.  R.  Alexander, and T.  Grandin. 2019. Effect of cap- Gilliam, J. N., J. K. Shearer, R. J. Bahr, S. Crochik, J. Woods, tive bolt gun length on brain trauma and post-stunning J. Hill, J. Reynolds, and J. D. Taylor. 2016. Evaluation of hind limb activity in finished cattle Bos taurus. Meat Sci. brainstem disruption following penetrating captive-bolt 155:69–73. doi:10.1016/j.meatsci.2019.05.004 shot in isolated cattle heads: comparison of traditional NPB. 2016. On-Farm euthanasia of swine: recommendations and alternative shot-placement landmarks. Anim. Welf. for the producer. Tech. Bull. No. 04970-11/16. National 25:347–353. doi:10.7120/90627286.25.3.347 Pork Board, Des Moines, IA. Gilliam,  J.  N., J.  K.  Shearer, J.  Woods, J.  Hill, J.  Reynolds, Wagner,  D.  R., H.  C.  Kline, M.  S.  Martin, L.  R.  Alexander, J. D. Taylor, R. J. Bahr, S. Crochik, and T. A. Snider. 2012. T. Grandin, and L. N. Edwards-Callaway. 2019. The effects Captive-bolt euthanasia of cattle: determination of opti- of bolt length on penetration hole characteristics, brain mal-shot placement and evaluation of the Cash Special damage and specified-risk material dispersal in finished Euthanizer Kit for euthanasia of cattle. Anim. Welf. cattle stunned with a penetrating captive bolt stunner. 21:99–102. doi:10.7120/096272812X13353700593806 Meat Sci. 155:109–114. doi:10.1016/j.meatsci.2019.05.006 Gilliam,  J.  N., J.  Woods, J.  Hill, J.  K.  Shearer, J.  Reynolds, Woods,  J., J.  K.  Shearer, and J.  Hill. 2010. Recommended and J.  D.  Taylor. 2018. Evaluation of the CASH on-farm euthanasia practices. In: T.  Grandin, editor, Dispatch Kit combined with alternative shot placement Improving animal welfare: a practical approach. CAB landmarks as a single-step euthanasia method for International, Oxfordshire, UK. p. 195–201. Translate basic science to industry innovation http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Translational Animal Science Oxford University Press

Quantification of cooling effects on basic tissue measurements and exposed cross-sectional brain area of cadaver heads from market pigs

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© The Author(s) 2021. Published by Oxford University Press on behalf of the American Society of Animal Science.
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Abstract

Quantification of cooling effects on basic tissue measurements and exposed cross- sectional brain area of cadaver heads from market pigs † ‡ || ‡ ‡ Karly N. Anderson, Sarah E. Albers, Kaysie J. Allen, Katherine D. Bishop, Brian J. Greco, ‡ $ ‡ ‡,1 Christina M. Huber, Ashlynn A. Kirk, Hannah Olsen, and Kurt D. Vogel Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, USA; Department of Animal and Food Science, University of Wisconsin–River Falls, || River Falls, WI, USA; Department of Animal and Dairy Sciences, University of Wisconsin–Madison, Madison, WI, USA; and Center for Animal Welfare, Department of Animal Science, University of California–Davis, Davis, CA, USA ABSTRACT: The objective of this project was to the plane of the bolt path immediately prior to determine the impact of cooling on the soft tissue and immediately after the refrigeration treatment. thickness, cranial thickness, and cross-sectional Measurements were performed by two observers. brain area of cadaver heads from market pigs. Across all measurements, mean interobserver coef- Documenting the effect of cooling on tissue dimen- ficient of variation was 11.3 ± 0.6%. The soft tissue sions of swine heads is valuable and important for caudal to the bolt path was different (P = 0.0120) future investigations of physical stunning and eu- between treatments (CHILLED: 6.4  ± 0.2  mm; thanasia methods that use cadaver heads. Scalded UNCHILLED: 7.2  ± 0.2  mm). The soft tissue and dehaired cadaver heads with intact jowls were thickness rostral to the bolt path was different sourced from market pigs stunned with CO gas. (P  =  0.0378) between treatments (CHILLED: After transport to the data collection location, a 5.5  ± 0.2  mm; UNCHILLED: 6.1  ± 0.2  mm). penetrating captive bolt (PCB) shot (Jarvis Model Cranial thickness caudal to the bolt path was not PAS—Type P 0.25R Caliber Captive Bolt Pistol different (P = 0.8659; CHILLED: 18.1 ± 0.6 mm; with Medium Rod Assembly and Blue Powder UNCHILLED: 18.3 ± 0.6 mm), nor was there a Cartridges) was applied in the frontal position. significant difference (P = 0.2593) in cranial thick- Following PCB application, each head (n  =  36) ness rostral to the bolt path between treatments underwent an UNCHILLED treatment followed (CHILLED: 16.2  ± 0.6  mm; UNCHILLED: by CHILLED treatment. The UNCHILLED 15.2 ± 0.6 mm). Cross-sectional brain area did not treatment involved images collected immediately differ (P = 0.0737; CHILLED: 3633.4 ± 44.1 mm; after splitting each head along the bolt path, and UNCHILLED: 3519.9 ± 44.1 mm). A correction the CHILLED treatment involved images of the factor of 1.12 was determined from this study for same heads after storage in a walk-in cooler for cases where estimation of UNCHILLED soft 24 h at 2 to 4°C. All measurements for each treat- tissue thickness from CHILLED soft tissue thick- ment were collected from images of the heads on ness is necessary. Keywords: captive bolt, euthanasia, slaughter, stunning, swine © The Author(s) 2021. Published by Oxford University Press on behalf of the American Society of Animal Science. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribu- tion, and reproduction in any medium, provided the original work is properly cited. Transl. Anim. Sci. 2021.5:1-6 doi: 10.1093/tas/txab001 Corresponding author: kurt.vogel@uwrf.edu Received November 15, 2020. Accepted January 6, 2021. 1 Anderson et al. INTRODUCTION by the United States Department of Agriculture Food Safety and Inspection Service (USDA FSIS) Penetrating captive bolt (PCB) is a method of in accordance with the regulations in 9 CFR 313. euthanasia and stunning approved for a variety The heads used in this study were acquired as meat of livestock species by the American Veterinary products that were suitable for human consump- Medical Association (AVMA 2016, 2020), the tion. The exemption from IACUC approval fol- National Pork Board (NPB) and American lowed the precedent established by Anderson et al. Association of Swine Veterinarians (AASV) for (2019). swine (NPB, 2016), and the American Association of Bovine Practitioners (AABP, 2019) for cattle. Description of Cadaver Heads There has been growing interest in assessing the implications of bolt length used with cattle Thirty-six heads, scalded and dehaired with (Kline et al., 2019; Wagner et al., 2019), physical skin on and jowls intact, were obtained from pigs landmarks for PCB placement for cattle (Gilliam that were commercially slaughtered at a regional et  al., 2012, 2016, 2018), and alternative PCB processing facility under federal inspection. The placement in swine (Anderson et  al., 2019). The heads were inspected and passed for human con- brain is a semifluid structure that makes the as- sumption. The estimated body weight (BW) of the sessment of brain damage attributed to the PCB pigs was 136 kg, and they were approximately 6 mo itself difficult due to tissue distortion during the of age. Exact BW and age of each pig was not avail- head splitting process (Kline et al., 2019). At the able, so estimates of age and weight were based on time of our study, there did not appear to be any the purchasing specifications of the establishment. published data to quantify the impact of cooling Each head was removed from its respective car- on the tissue parameters of cadaver heads of any cass via knife incision between the atlas and axis by species following the application of a captive plant personnel. All heads were packaged in plastic bolt. Understanding and accounting for poten- bags and boxed prior to unrefrigerated transport tial changes in tissue dimensions associated with (distance traveled: 180 km) to the University of cooling are important for future investigations Wisconsin—River Falls Meat Science Laboratory related to the captive bolt stunning and euthan- where the project commenced within approximately asia of livestock species, as chilling allows for a 6 h of head collection. greater degree of accuracy when assessing brain damage because the bolt path remains clearly vis- Description of Captive Bolt Tool and Placement ible in cooled brain tissue. The objective of this study was to quantify The PCB device used in this study was the impact of cooling on the soft tissue thick- a Jarvis Model PAS—Type P 0.25R Caliber ness, cranial thickness, total tissue thickness, and Captive Bolt Pistol (order no.  4144035, Jarvis cross-sectional brain area of cadaver heads from Corp., Middletown, CT) equipped with market pigs following the application of a PCB Medium Stunning Rod Nosepiece Assembly shot to the common frontal location. Our hy- (order no.  3116604, Jarvis Corp.). Jarvis Blue pothesis was that UNCHILLED cadaver heads Powder Cartridges—0.25R Caliber, 3GR (order would display soft tissue thickness, cranial thick- no.  1176018, Jarvis Corp.) were utilized for all ness, total tissue thickness, and cross-sectional PCB applications in this study. All equipment brain area that was not different than CHILLED and placement procedures were the same as used cadaver heads. by Anderson et al. (2019). The PCB was placed in the frontal location as described by Woods et al. MATERIALS AND METHODS (2010) at 2.54 cm superior to a line drawn across the top of the eyes at the midline. To ensure con- Animal Use Protocol sistent placement and entry angle of the PCB, the It was not necessary to submit an animal use barrel of the captive bolt pistol was fitted with a protocol to the University of Wisconsin—River custom-fabricated flange. The flange maintained Falls Institutional Animal Care and Use Committee a perpendicular relationship between the PCB (IACUC) because live animals were not directly and frontal plate of the cranium. To prevent the manipulated in this study. The pigs from which the movement during PCB application, each head heads were obtained were slaughtered at a com- was placed on a solid surface and held firmly in mercial slaughter establishment under inspection place by the snout and the ears. Translate basic science to industry innovation Quantification of cooling effects Postapplication Head Processing cranium along the bolt path. This measurement was reported caudal and rostral to the bolt path. Total Following the application of the shot location tissue thickness (mm), which referred to the total treatment, each head was cut along the bolt path soft tissue and cranial thickness from the site of ap- with a meat band saw. Following each cut, digital plication to the interior surface of the cranium, was images were collected from both the left and right determined from the summation of the soft tissue sides of each exposed intracranial surface. Thermal and cranial thicknesses for each cadaver head. This images (Model E8, FLIR Systems, Boston, MA) measurement was reported caudal and rostral to were also collected from both the left and right the bolt path. Soft tissue thickness, cranial thick- sides of each exposed intracranial surface for tem- ness, and total tissue thickness were determined perature assessment. All images were collected by averaging the measurements from the right and with the thermal camera and digital camera posi- left halves each head for the rostral aspect and the tioned 54.6  cm directly above and perpendicular caudal aspect of the bolt path. Cross-sectional to the exposed cut surface. Following image collec- brain area (mm ) referred to the cross-sectional sur- tion, the two halves of each head were reassembled face area of the exposed brain area within the plane and wrapped with polyvinylchloride film prior to of the bolt travel as described by Anderson et  al. chilling for 24 h at 2 to 4°C. (2019). Measurements of cross-sectional brain area were calculated from both the right and left halves Thermal Image Collection and Analysis along the paths of bolt travel and averaged prior to statistical analysis. All measurements were repeated Temperature data were collected with a thermal 24 h after each head was placed under refrigeration. imaging camera (FLIR E8, FLIR Systems). The accuracy of temperature emission readings for this Statistical Analyses model was ±2°C or ±2% of reading, for ambient temperature 10 to 35°C and object temperature All continuous data for captive bolt applica- above 0°C. The camera also utilized Multi-Spectral tion treatment (UNCHILLED, CHILLED) effects Dynamic Imaging to enhance the thermal image were analyzed using models constructed within the with a visible camera detail based on a simultan- MIXED procedure of SAS (Statistical Analysis eously collected digital image. Thermal images System Institute, Inc., Cary, NC) with Kenward– were uploaded to a laptop computer and viewed on Roger denominator degrees of freedom designated FLIR Tools software (FLIR Systems) to determine within each model and mean separation performed maximum intracranial temperature. All digital im- with the Tukey’s test designation. For all ana- ages were also uploaded to a laptop computer for lyses, the experimental unit was individual head. tissue and area measurement collection. Significant differences in treatment effects were rec- ognized at α ≤ 0.05. Tissue and Cranial Measurements RESULTS AND DISCUSSION Measurements of soft tissue thickness (mm), cranial thickness (mm), and cross-sectional brain Tissue measurements, cross-sectional brain area (mm ; Figure  1) were determined from im- areas, weights, and temperatures collected from ages collected at the time of head processing for the this study can be observed in Table  1. Soft tissue control heads and 24  h after head processing for thickness was significantly different (P < 0.05) be- chilled heads. All images included a 15.0-cm ruler tween the UNCHILLED and CHILLED treat- that was used as a reference for an online irregular ments. There were no significant differences area calculator (SketchandCalc, iCalc, Inc., Palm (P > 0.05) in cranial thickness, total tissue thick- Coast, FL). All measurements were performed by ness, and cross-sectional brain area between the two trained observers. Across all measurements, the UNCHILLED and CHILLED treatments. Head mean interobserver percent coefficient of variation weight was not significantly different (P > 0.05) was 11.3  ± 0.6%. Soft tissue thickness referred to between the UNCHILLED and CHILLED treat- the tissue from the application site to the exterior ments. Cranial temperature was significantly dif- surface of the cranium. This measurement was re- ferent (P < 0.05) between the UNCHILLED and ported caudal and rostral to the bolt path. Cranial CHILLED treatments. thickness referred to the thickness from the exterior Soft tissue thickness caudal to the bolt path was surface of the cranium to the interior surface of the greater (P = 0.0120) in UNCHILLED heads (7.2 ± Translate basic science to industry innovation Anderson et al. Figure 1. Soft tissue thickness—the tissue from the application site to the exterior surface of the cranium along the bolt path; cranial thickness—the thickness from the exterior surface of the cranium to the interior surface of the cranium along the bolt path; brain area—the cross-sectional surface area of the exposed brain area within the plane of the bolt travel. Soft tissue thickness and cranial thickness were meas- ured at the rostral and caudal aspects of the bolt path on the right and left halves of each split head. Values were averaged prior to statistical analysis. Table 1.  Effects of cooling on tissue parameters and cross-sectional brain area of cadaver heads from market weight hogs assigned to an UNCHILLED and CHILLED treatment and sectioned by band saw following the plane of bolt travel (n = 36) Refrigeration treatment UNCHILLED CHILLED Dependent variable SEM n SEM n Pooled SE P-value Soft tissue thickness caudal to bolt path, mm 7.2 36 6.4 36 0.2 0.0120 Soft tissue thickness rostral to bolt path, mm 6.1 36 5.5 36 0.2 0.0378 Cranial thickness caudal to bolt path, mm 18.3 35 18.1 36 0.6 0.8659 Cranial thickness rostral to bolt path, mm 15.2 36 16.2 36 0.6 0.2593 Total tissue thickness caudal to bolt path, mm 24.5 35 24.5 36 0.6 0.2577 Total tissue thickness rostral to bolt path, mm 21.3 36 21.7 36 0.7 0.6730 Cross-sectional brain area, mm 3519.9 30 3633.4 31 44.1 0.0737 Head weight, kg 5.8 36 5.6 36 0.1 0.1824 Exposed head temperature, °C 30.6 36 2.7 36 0.1 <0.0001 Refrigeration treatment: UNCHILLED—Data from images collected immediately after captive bolt application; CHILLED—data from im- ages collected 24 h after captive bolt application and refrigeration at 2 to 4°C. Translate basic science to industry innovation Quantification of cooling effects 0.2  mm) than CHILLED heads (6.4  ± 0.2  mm). heads for use in future investigations. The following Soft tissue thickness rostral to the bolt path was formula was used as follows: (UNCHILLED soft also greater (P  =  0.0378) in UNCHILLED heads tissue thickness/CHILLED soft tissue thickness). (6.1  ± 0.1  mm) than CHILLED heads (5.5  ± The caudal and rostral soft tissue thicknesses were 0.2 mm). Cranial thickness caudal to the bolt path averaged for each head within each treatment group was not different (P  =  0.8659) in UNCHILLED prior to calculation of the correction factor. (18.3  ± 0.6  mm) heads than CHILLED (18.1  ± 0.6  mm) heads, nor was cranial thickness ros- IMPLICATIONS tral to the bolt path different (P  =  0.2593) be- As a result of the greater soft tissue thickness tween treatments (UNCHILLED: 15.2 ± 0.6 mm; in UNCHILLED heads compared to CHILLED CHILLED: 16.2 ± 0.6 mm). Total tissue thickness heads, a correction factor of 1.12 was determined caudal to the bolt path did not differ (P = 0.2577) for the prediction of UNCHILLED soft tissue between UNCHILLED (24.5 ± 0.6 mm) heads and thickness from CHILLED soft tissue thickness. Our CHILLED heads (24.5  ± 0.6  mm). Total tissue results did not identify a need for a correction factor thickness rostral to the bolt path was also not dif- when determining UNCHILLED cranial thickness, ferent (P = 0.6730) between UNCHILLED (21.3 ± total tissue thickness, or cross-sectional brain area 0.7  mm) heads and CHILLED (21.7  ± 0.7  mm) from CHILLED heads. It is important to observe heads. There was no difference (P  =  0.0737) differences in tissue damage in future investigations in exposed cross-sectional brain area between of cooling effects on cadaver swine heads as this UNCHILLED (3519.9  ± 44.1  mm ) heads and study was solely focused on detecting differences in CHILLED (3633.4 ± 44.1 mm ) heads. Cranial tem- tissue dimensions. Ultimately, the documentation of perature was greater (P ˂ 0.0001) in UNCHILLED the effect of cooling on tissue dimensions of swine (30.6  ± 0.1°C) heads than CHILLED (2.7  ± heads is valuable and important for future investiga- 0.1°C) heads. tions of physical stunning and euthanasia methods In an assessment of physical landmarks for that use cadaver heads as a model. the PCB euthanasia of cattle, Gilliam et al. (2012) concluded that the variable freezing time and 36-h thaw time may have resulted in the failure of trau- ACKNOWLEDGMENTS matic brain injury scores, although the method The authors thank the commercial slaughter they used had been validated in heads from ani- establishment that provided the cadaver heads for mals that were recently shot with a PCB or bullet this research and the data collection assistance of and not frozen. Gilliam et al. (2016) reported that J.  Bignell and K.  Heussner. The provision of cap- that brain tissue was softened from freezing and tive bolt stunning equipment by Jarvis Corporation thawing cadaver bovine heads, which resulted in and technical support by Bunzl Processor division the tissue collapsing into the bolt path before CT was greatly appreciated. This project was funded by scans of the head, which may have contributed a grant from the University of Wisconsin - River to the observation of shallow penetration depth Falls Undergraduate Research, Scholarly, and from computerized tomography (CT) scans of Creative Activity Program. heads from mature bulls. Conflict of interest statement. None declared. Kline et al. (2019) reported challenges in the as- sessment of damage to brain tissue following the PCB stunning of cattle, due to the gelatinous na- LITERATURE CITED ture of the brain, and recommended a 12- to 24-h AABP. 2019. Guidelines for the humane euthanasia of chill time prior to splitting skulls in future studies cattle. https://aabp.org/Resources/AABP_Guidelines/ for more accurate assessment of brain damage. In EUTHANASIA-2019.pdf (Accessed 6 September 2020). a related study, cattle heads were collected from a Anderson,  K., E.  Ries, J.  Backes, K.  Bishop, M.  Boll, processing plant and chilled at 0°C for 24 h prior to E. Brantner, B. Hinrichs, A. Kirk, H. Olsen, B. Risius, et al. the assessment of damage to specific regions of the 2019. Relationship of captive bolt stunning location with basic tissue measurements and exposed cross-sectional brain and challenges with the assessment of brain brain area in cadaver heads from market pigs. Transl. damage were not noted (Wagner et al., 2019). Anim. Sci. 3:1405–1409. doi:10.1093/tas/txz097 The results in our study were used to calculate a A VMA. 2016. A VMA guidelines for the humane slaughter of ani- correction factor that could be used to estimate the mals: 2016 Edition. https://www.avma.org/KB/Resources/ unchilled soft tissue thickness of market pig heads at Reference/AnimalWelfare/Documents/Humane-Slaughter- Guidelines.pdf (Accessed 5 March 2019). the frontal PCB site from measurements of chilled Translate basic science to industry innovation Anderson et al. AVMA. 2020. AVMA guidelines for the euthanasia of ani- cattle of various ages. Anim. Welf. 27:225–233. mals: 2020 Edition. https://www.avma.org/sites/de- doi:10.7120/09627286.27.3.225 fault/files/2020-01/2020-Euthanasia-Final-1-17-20.pdf Kline,  H.  C., D.  R.  Wagner, L.  N.  Edwards-Callaway, (Accessed 9 April 2020). L.  R.  Alexander, and T.  Grandin. 2019. Effect of cap- Gilliam, J. N., J. K. Shearer, R. J. Bahr, S. Crochik, J. Woods, tive bolt gun length on brain trauma and post-stunning J. Hill, J. Reynolds, and J. D. Taylor. 2016. Evaluation of hind limb activity in finished cattle Bos taurus. Meat Sci. brainstem disruption following penetrating captive-bolt 155:69–73. doi:10.1016/j.meatsci.2019.05.004 shot in isolated cattle heads: comparison of traditional NPB. 2016. On-Farm euthanasia of swine: recommendations and alternative shot-placement landmarks. Anim. Welf. for the producer. Tech. Bull. No. 04970-11/16. National 25:347–353. doi:10.7120/90627286.25.3.347 Pork Board, Des Moines, IA. Gilliam,  J.  N., J.  K.  Shearer, J.  Woods, J.  Hill, J.  Reynolds, Wagner,  D.  R., H.  C.  Kline, M.  S.  Martin, L.  R.  Alexander, J. D. Taylor, R. J. Bahr, S. Crochik, and T. A. Snider. 2012. T. Grandin, and L. N. Edwards-Callaway. 2019. The effects Captive-bolt euthanasia of cattle: determination of opti- of bolt length on penetration hole characteristics, brain mal-shot placement and evaluation of the Cash Special damage and specified-risk material dispersal in finished Euthanizer Kit for euthanasia of cattle. Anim. Welf. cattle stunned with a penetrating captive bolt stunner. 21:99–102. doi:10.7120/096272812X13353700593806 Meat Sci. 155:109–114. doi:10.1016/j.meatsci.2019.05.006 Gilliam,  J.  N., J.  Woods, J.  Hill, J.  K.  Shearer, J.  Reynolds, Woods,  J., J.  K.  Shearer, and J.  Hill. 2010. Recommended and J.  D.  Taylor. 2018. Evaluation of the CASH on-farm euthanasia practices. In: T.  Grandin, editor, Dispatch Kit combined with alternative shot placement Improving animal welfare: a practical approach. CAB landmarks as a single-step euthanasia method for International, Oxfordshire, UK. p. 195–201. Translate basic science to industry innovation

Journal

Translational Animal Science – Oxford University Press

Published: Jan 11, 2021

Keywords: captive bolt; euthanasia; slaughter; stunning; swine

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