Penetrative mechanical stunning (P) caused smaller increases in plasma
adrenalin concentration (Figure 1) when compared to the HPP and
LPP groups, suggesting animals experienced less distress. Although
the purpose of stunning is to eliminate animal suffering during the
slaughter procedures, as measured by plasma levels of ACTH (Figure
2) and noradrenalin (Figure 3), HPP induced a greater physiological
stress reaction when compared to P. Earlier studies suggested that,
although both P and HPP resulted in similar structural tissue damage,
focal injury was more severe in the former, while the latter caused more
widely distributed damage. Penetrative captive bolt stunning was more
effective, and the likelihood of error was lower than for non-penetrative
stunning.