“Pigs do suffer in Butina paternoster systems during 90% (CO2) stunning and the stun is not immediate."

"Behavioural abnormalities, significant decreases in the heart rate, the respiratory rate and the oxygen saturation (p < or = 0.001) including a cardiac arrhythmia (extrasystoles) underline the impression that CO2 inhalation anaesthesia negatively affects animal welfare."

“There is clear evidence in the human literature that CO2 exposure is painful and distressful, while the non-human literature is equivocal.

"High concentrations of CO2 have been known for decades to cause pain, fear and distress in pigs before loss of consciousness, and the stunning method is clearly associated with animal welfare concerns."

“When an atmosphere of 90 vol% CO2 is applied, most animals are already dead before bleeding commences." "It seems necessary to revise the current legislation on gas stunning and to look in greater detail in the effects of CO2 stunning on the welfare of slaughter pigs.”

“The main cause of respiratory distress is due to increased CO2 levels (Raj, 2006), a strong respiratory stimulator that induces a sense of breathlessness and air hunger before loss of consciousness (Beausoleil and Mellor, 2015).” (3.2.4. Controlled atmosphere stunning method 1: CO2 at high concentrations) “It has been demonstrated that pigs find CO2 in high concentrations aversive and, given a free choice, they avoid such atmospheres (Raj and Gregory, 1995; EFSA, 2004). CO2 itself causes irritation of the nasal mucosa and exposure is therefore inducing a painful sensation (Steiner et al., 2019). CO2 has the potential to cause welfare consequences via three different mechanisms: (1) pain due to formation of carbonic acid on respiratory and ocular membranes, (2) production of so‐called air hunger and a feeling of breathlessness and (3) direct stimulation of ion channels within the amygdala associated with the fear response (Raj, 2006; Beausoleil and Mellor, 2015; AVMA, 2020).”

"Loss of posture was on average observed in both groups 10 s before EEG-based loss of consciousness. Furthermore, 88% of 80C pigs and 94% of 95C pigs demonstrated muscular contractions before loss of consciousness."

“If the pigs violently attempt to escape when they first inhale the gas, this is not acceptable." "Observations by people working in the industry indicate that 7% to 8% may have severe lung lesions.” "Machines will require the use of video cameras installed in the pit.” “I wanted to try to fix this problem,” Grandin adds. “They didn’t want to look inside the box.”