Head to back stunning, regardless of stun duration or current level applied, contributed to a higher incidence of bone fractures, particularly spinal fractures, compared with CO2 stunning. As the rear electrode on the HB handpiece was fixed in position, the actual position of the rear electrode along the backbone of the animal was not always the same as this was dependent upon the size of the pig being stunned. This may partly explain variations in the site of spinal fractures found in carcasses in this study. Wotton et al. (1992), however, found that there was no single rear electrode position in
head to back stunning that ensured both 100% cardiac fibrillation and no bone fractures. Interestingly, although broken vertebrae resulted from HB stunning of pigs, it did not necessarily result in ecchymosis-affected pork in the LTL muscle