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

Abstract

The objective of this project was to determine the impact of cooling on the soft tissue thickness, cranial thickness, and cross-sectional brain area of cadaver heads from market pigs. Documenting the effect of cooling on tissue dimensions of swine heads is valuable and important for future investigations of physical stunning and euthanasia methods that use cadaver heads. Scalded and dehaired cadaver heads with intact jowls were sourced from market pigs stunned with CO2 gas. After transport to the data collection location, a penetrating captive bolt (PCB) shot (Jarvis Model PAS—Type P 0.25R Caliber Captive Bolt Pistol with Medium Rod Assembly and Blue Powder Cartridges) was applied in the frontal position. Following PCB application, each head (n = 36) underwent an UNCHILLED treatment followed by CHILLED treatment. The UNCHILLED treatment involved images collected immediately after splitting each head along the bolt path, and the CHILLED treatment involved images of the same heads after storage in a walk-in cooler for 24 h at 2 to 4°C. All measurements for each treatment were collected from images of the heads on the plane of the bolt path immediately prior to and immediately after the refrigeration treatment. Measurements were performed by two observers. Across all measurements, mean interobserver coefficient of variation was 11.3 ± 0.6%. The soft tissue caudal to the bolt path was different (P = 0.0120) between treatments (CHILLED: 6.4 ± 0.2 mm; UNCHILLED: 7.2 ± 0.2 mm). The soft tissue thickness rostral to the bolt path was different (P = 0.0378) between treatments (CHILLED: 5.5 ± 0.2 mm; UNCHILLED: 6.1 ± 0.2 mm). Cranial thickness caudal to the bolt path was not different (P = 0.8659; CHILLED: 18.1 ± 0.6 mm; UNCHILLED: 18.3 ± 0.6 mm), nor was there a significant difference (P = 0.2593) in cranial thickness rostral to the bolt path between treatments (CHILLED: 16.2 ± 0.6 mm; UNCHILLED: 15.2 ± 0.6 mm). Cross-sectional brain area did not differ (P = 0.0737; CHILLED: 3633.4 ± 44.1 mm; UNCHILLED: 3519.9 ± 44.1 mm). A correction factor of 1.12 was determined from this study for cases where estimation of UNCHILLED soft tissue thickness from CHILLED soft tissue thickness is necessary.

Quantification of cooling effects on basic tissue measurements and exposed cross-sectional brain area of cadaver heads from Holstein cows > 30 mo of age

“…This followed the precedent set by Anderson et al. (2019 , 2021a , 2021b ) and Hamilton et al. (2023) for an exemption from Institutional Animal Care and Use Committee approval.…”

“…A power calculation to determine sample size was conducted using the POWER procedure of SAS 9.4 (Statistical Analysis System Institute, Inc., Cary, NC) with the following parameters: detectable difference of 0.8, SD of 1.2, and power of 0.8. The detectable difference was derived from soft tissue thickness measurements caudal to the bolt path of market hogs at 0 and 24 h of refrigeration, and the SD value was back-calculated from the SE values for the same measurements ( Anderson et al., 2021b ). All heads were removed from their respective carcasses by plant personnel via knife incision between the atlas and axis.…”

“…(2019) described that assessing macroscopic brain damage following PCB stunning on heads from fed cattle that were not refrigerated was difficult. Specifically, differentiating damage from the PCB and tissue distortion that may occur during the splitting process may be difficult with heads that are not cooled prior to splitting ( Kline et al., 2019 ; Anderson et al., 2021b ). Anderson et al.…”

“…Specifically, differentiating damage from the PCB and tissue distortion that may occur during the splitting process may be difficult with heads that are not cooled prior to splitting ( Kline et al., 2019 ; Anderson et al., 2021b ). Anderson et al. (2021b) evaluated the impact of cooling on tissue parameters associated with a frontal PCB application for market hogs.…”

“…Understanding whether tissue parameters change with the cooling of cadaver heads is important for future studies related to PCB stunning and euthanasia. Cooling cadaver heads prior to splitting allows for improved accuracy in brain damage assessments because there is less tissue distortion from the splitting process and the bolt path is visually distinguished ( Anderson et al., 2021b ).…”