Preparatory Work for Future Development of Four Scientific Opinions on Monitoring Procedures at Slaughterhouses

The objective of this review was to summarize the currently available data describing the sensitivity and specificity of indicators of unconsciousness and death in the following stun-kill methods and species combinations: 1) penetrative captive bolt for bovine animals, 2) head-only electrical stunning for pigs, 3) headonly electrical stunning for sheep and goats, 4) electrical waterbath for poultry (chickens and turkeys), 5) carbon dioxide at high concentration for pigs, 6) all authorized gas methods to slaughter chickens and turkeys (carbon dioxide at high concentration, carbon dioxide in two phases, carbon dioxide associated with inert gases and inert gases alone), 7) slaughter without stunning for bovine animals, 8) slaughter without stunning for sheep and goats, 9) slaughter without stunning for chickens and turkeys. The reference tests for unconsciousness and death were to have been measured using electroencephalography (EEG). The definition of unconsciousness and death based on EEG were not specified, and the definition used by authors was reported. The index tests of interest were a variety of indicators requested by the funding agency such as no corneal reflex and immediate collapse. The index tests differed by stun-kill methods and species combination. A comprehensive search identified 22 publications contained 24 species-stun/kill method combinations. No studies explicitly reported the sensitivity and specificity of the indicators in conscious and unconscious animals. Many studies reported the proportion of stunned animals with indicators, rather than the proportion of unconscious or conscious animals at a set time point with the indicators. Such data could not be translated into sensitivity and specificity. Other studies reported the average time to occurrence of an indicator or average time to cessation of the indicators. Such data cannot be translated into sensitivity and specificity estimates without knowledge of the joint distributions

CO2 induced acute respiratory acidosis and brain tissue intracellular pH: a P-31 NMR study in swine

High concentration carbon dioxide (CO2) is used to promote pre-slaughter anaesthesia in swine and poultry, as well as short-lasting surgical anaesthesia and euthanasia in laboratory animals. Questions related to animal welfare have been raised, as CO2 anaesthesia does not set in momentarily. Carbon dioxide promotes anaesthesia by lowering the intracellular pH in the brain cells, but the dynamics of the changes in response to a high concentration of CO2 is not known. Based on P-31 NMR spectroscopy, we describe CO2-induced changes in intracellular pH in the brains of five pigs inhaling 90% CO2 in ambient air for a period of 60 s, and compare the results to changes in arterial blood pH, P-CO2, O-2 saturation and HCO(3)(-)concentration. The intracellular pH paralleled the arterial pH and P-CO2 during inhalation of CO2; and it is suggested that the acute reaction to CO2 inhalation mainly reflects respiratory acidosis, and not metabolic regulation as for example transmembrane fluxes of H+/HCO3-. The intracellular pH decreased to approximately 6.7 within the 60 s inhalation period, and the situation was metabolically reversible after the end of CO2 inhalation. The fast decrease in intracellular pH supports the conclusion that high concentration CO2 leads to anaesthesia soon after the start of inhalation