Controlled atmosphere stunning of poultry.

For more than 20 yr Stork PMT has carried out a lot of research into stunning and killing of poultry with electrical and mechanical methods and by applying gas mixtures. For the past 3 yr, research was carried out under the European umbrellas (AIR and EUREKA) together with BOC, The Spelderholt, CIVO, and Bristol University. This research program involved tests on broiler stunning or killing with various gas mixtures. The effect on meat quality, bleeding, and plucking was studied, as well as the use of gas as a humane way of killing broilers. The study of meat quality was based on tenderness tests conducted on the shear force principle, meat color, and drip and cooking losses. The percentage of blood loss in bleeding, blood spots, and the amount of blood in the veins in relation to the gas mixtures and time of hanging were measured. The effect of gas killing on the plucking characteristics was studied by determining the feather release force and product handling. The behavior of the birds, reflexes, the onset of convulsions, electroencephalograms, and evoked responses were studied in relation to the humanness of gas killing. Anoxia generated through argon or a mixture of argon and carbon dioxide or hypercapnic hypoxia seems to be very promising. The tests revealed that meat tenderness and drip losses will improve. The blood spots, especially those on the thighs and breasts caused by stunning and hanging, disappear altogether. It also appeared that animal welfare will be drastically improved. From a technological point of view, broiler killing in a controlled gas atmosphere is considered to be the optimal process. However, successful introduction of the process requires legislative changes and poultry processors must be made aware of its economic benefits.