Cattle breed and head dimension effects on the performance of a captive bolt stunner equipped with three different length bolts
D. R. Wagner H. C. Kline M. S. Martin K. Vogel L. Alexander T. Grandin
Journal of Animal Science, Volume 95, Issue suppl_4, 1 August 2017, Pages 10, https://doi.org/10.2527/asasann.2017.020
Published: 01 August 2017
Abstract
Captive bolt stunning is commonly used as a means of quickly and effectively rendering cattle insensible prior to slaughter. Effective stunning of cattle is partially ensured by proper placement of the device, which may be breed dependent. For Holsteins, stun placement is typically recommended 2.5 cm above common placement for other breeds. The purpose of this study was to determine if head dimensions and brain location differ between Holstein and non-Holstein breeds. This study also examined the effects of different bolt lengths on physical brain damage. It was hypothesized that head size and brain damage would not differ based on bolt length or breed. This study used a randomized, unbalanced block design, with treatment blocked by day. Experimental unit was animal, and analyses were performed using t-tests in SAS 9.4 (SAS Inst. Inc., Cary, NC). The stunner used was a Jarvis USSS-1 (Jarvis Products Corp., Middletown, CT), a penetrating, pneumatic captive bolt gun. For brain damage assessment, 292 heads were randomly sampled across 3 collection periods, with an approximately equal split between Holstein and non-Holstein breeds. Each period was assigned the control bolt (CON), medium bolt (MED), or long bolt (LON), with lengths of 15.2, 16.5, and 17.8 cm, respectively. Heads were collected, immediately measured, and chilled for splitting and damage analysis at the Colorado State University Necrology Laboratory (Colorado State University Veterinary Teaching Hospital, Fort Collins, CO). For head dimension assessment, 426 heads equally distributed between Holstein and non-Holstein breeds were sampled. Head width, poll to orbit, right orbit to poll, and left orbit to poll did not differ between breeds (P > 0.13). Head length and orbit to nose length were greater for Holsteins (P = 0.0046). Brain size, length, and width as well as skull thickness did not differ between breeds (P > 0.32). Stunning metrics included bolt entrance hole diameter, which was greatest for the LON, least for the MED, and intermediate for the CON (P < 0.0001). Bolt penetration depth was greatest for the MED (P < 0.0001). Sagittal brain damage was least for the CON, with greater damage measured on the MED and LON (P < 0.0001). Dorsal damage was least for the CON and increased for the MED and LON (P < 0.0001). The data in this study suggest that differing bolt lengths affect brain damage and that head dimensions appear to be different between breeds only in nose length, indicating that current recommendations for differing stun placement based on breed may need to be reevaluated.
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