CO2 stunning may compromise swine welfare compared with electrical stunning

The effects of two different stunning methods on critical blood values in fattening pigs at a federal inspection slaughtering plant were monitored. A total of 658 pigs from the same genetic line and origin, were randomly assigned to 3 treatments: reference baseline levels (resting pigs; T1), stunning with CO2 (T2) and stunned electrically (T3). Energetic profile, acid imbalance and blood gas levels, were monitored. Significant differences (p ⩽ 0.05) between treatments for all variables were found, CO2 stunned pigs showed hypercapnia, hypercalcemia, hyperglucemia, lactic acidemia, and an increase in haematocrit, coupled with reduced pH, PO2PO2, and Na; electrically stunned pigs had reduced blood pH, PCO2PCO2 and PO2PO2. The remaining indicators were increased in relation to the resting swine. Thus CO2 stunning leads to a major imbalance because of mineral and acid base gaseous interchange, compared to electric stunning, thus possibly compromising animal welfare.