Evaluation of a gas stunning equipment used for turkeys under slaughterhouse conditions

Physiological responses (eyelid closure and interphalangeal reflex) and meat quality (pH-value and electrical conductivity) of slaughter turkeys were measured after being stunned in a V-shaped tunnel in an increasing carbon dioxide (CO2)-atmosphere compared to a gas mixture of CO2 and argon (Ar) under practical conditions in a commercial slaughterhouse in order to assess the turkey's state of consciousness. Stick blood was analysed for stress parameters (lactate, catecholamines, corticosterone).After CO2-only-stunning, 77% of the turkeys had closed eyes and 61% of the birds had their eyes shut after being stunned with CO2&Ar. Only one bird showed an answer to the interphalangeal reflex (after CO2&Ar-stunning). Lower values of blood stress parameters were found after CO2-only-stunning, e.g. 37 nmol/l corticosterone (CO2&Ar) in comparison to 28 nmol/l (CO2-only-stunning). We determine that CO2-only-stunning seemed to be more advantageous in this approach but future constructural improvements will be important to optimize this stunning system.