Low atmospheric pressure stunning as a new method for stunning broilers in Germany under ethological aspects

According to Council Regulation (EC) No 1099/2009, poultry must be stunned before slaughter or killing by using an electrical water bath or controlled atmosphere stunning. Low atmospheric pressure stunning (LAPS) is a novel approach to stunning poultry without process gases. The animals are placed into a sealed chamber, and the air pressure is reduced by a specific 2-phased pump curve to reach a target level of decompression. During a LAPS cycle, air oxygen decreases to under 5 % of the initial oxygen concentration and leads to unconsciousness of the animals by hypoxia. In 2018, LAPS was approved as a stunning method in the European Union (Commission Implementing Regulation [EU] 2018/723). The aim of this study was to evaluate LAPS in Germany under animal welfare aspects. On 9 trial days, 35 Ross 308 broilers were stunned using a LAPS cycle with a decompression curve in accordance with Commission Implementing Regulation (EU) 2018/723. Individual video recordings of the broilers were analyzed. The ethogram used to interpret animal behavior consisted of aversive reactions, indicators of consciousness, and indicators of unconsciousness. Additionally, microclimatic and biological factors such as age, sex, and body weight potentially influencing the LAPS cycle were recorded. The results showed that up to 43 seconds after starting the LAPS cycle, only indicators of consciousness were recorded. From 248 seconds after starting the LAPS cycle, only indicators of unconsciousness occurred. During the interval between 44 and 247 seconds in the LAPS cycle, indicators of both consciousness and unconsciousness were observed, which impaired the evaluation of whether animals were conscious or unconscious. Aversive reactions were frequently observed during this intermediate phase. Even though Commission Implementing Regulation (EU) 2018/723 lists LAPS as stunning method for slaughtering and killing broilers, further research on welfare aspects is necessary. The results of this study indicate difficulties in determining the exact time when the animals become unconscious and whether aversive reactions are still consciously perceived.