Description of tissue profiles, thalamic location, and recommended penetrating captive bolt placement in cadaver heads from domesticated 24- to 48-mo-old male yaks ().

Yaks are a domesticated species utilized for meat, fiber, and transportation in many countries. In the United States, yak meat is growing in popularity due to its classification as a "healthy" meat. Penetrating captive bolt (PCB) is an approved method of preslaughter stunning and euthanasia for cattle. At the time of our study, peer-reviewed literature or industry guidelines for PCB stunning or euthanasia did not appear to exist for yaks. This study aimed to identify and describe an ideal placement based on the location of the thalamus, part of the brain that is important for sensibility, and to describe the tissue depths at this placement. To do this, 10 hide-on cadaver heads from yaks were sourced from a population of 30 yaks aged 24 to 48 mo, which had a mean hot carcass weight of 180.1 ± 52.0 kg (±SD). Source animals were stunned in a frontal location with a handheld PCB during normal slaughter procedures at the collaborating slaughter establishment. Cadaver heads were stored in a walk-in freezer for 96 d before head processing. Head weight, total head length, horn tip spread, and horn base circumference were measured. Heads were split down the midline using a band saw. Heads were imaged and tissue thicknesses of the exposed surface of each head were measured. Thalamic depth and measurements to describe the location of the thalamus relative to external head anatomy were recorded from these images. Results are reported as mean ± SD. On average, the total length of the head from the poll to the nose was 37.74 ± 2.83 cm. The center of the thalamus was located 11.86 ± 1.32 cm below the poll: 23.88 ± 1.56% down the frontal plane of the head. The exposed diameter of the thalamus on the frontal plane of the head was 3.43 ± 0.31%. Thus, an ideal PCB placement for yaks is located approximately 25% of the way down the frontal plane of the face of the animal. Tissue depth measurements are reported as mean ± SD followed by a 97.5% one-sided upper reference limit (URL). Soft tissue thickness was 16.03 ± 3.26 mm (URL: 23.77 mm), cranial thickness was 30.69 ± 4.34 mm (URL: 40.97 mm), and total tissue thickness was 46.71 ± 7.15 mm (URL: 63.68 mm). Thalamic depth was 92.22 ± 11.60 mm (URL: 119.74 mm). These results show that an ideal PCB placement for yaks is located at 23.88 ± 1.56% of the distance from the poll to the nose down the frontal plane of the head and a penetration depth of 92.22 ± 11.60 mm is required to reach the thalamus.