At the time of killing, animals are not always stunned, or are stunned ineffectively.
This implies that animals can still be conscious when bleeding starts. Despite the fact that pre-slaughter stunning is mandatory under the EU Regulation 1099/2009 (Slaughter Regulation) a derogation is foreseen for slaughter carried out in the context of religious rites.
This type of slaughter, along with the use of ineffective stunning methods, are currently the major drivers of animal suffering in slaughterhouses in the European Union. For instance, in the case of electrical water baths used for stunning poultry, birds may miss the electrified water bath completely or partially. Animals can lift their heads before entering the water, or there can be difficulties in achieving the suitable amperage for every single bird entering the water bath.
Certain stunning methods do not induce instantaneous and painless unconsciousness. For instance, high concentration CO2 stunning causes pain and distress for pigs from first exposure to the gas to loss of consciousness, which can take up to a minute to occur, yet it is used in the majority of large EU pig slaughterhouses as it allows for faster operations and more uniform meat quality. Footage of the suffering inflicted during this stunning procedure released by animal advocacy organisations has sparked outrage in the EU and internationally.
Additionally, staff training and skill level play a crucial role in determining animal welfare at slaughter. The EFSA recently identified a vast range of welfare problems occurring in poultry and rabbits at slaughter that are associated with skill level, as well as the level of attention of the people performing the slaughtering.