Effect of frequency at head only electrical stunning of pigs on the efficiency of stunning in commercial conditions

SUMMARY Background: Council Regulation (EC) No 1099/2009 on the protection of animals at the time of killing requires that animals must be rendered unconscious and insensible by stunning and they must remain so until death occurs through bleed ing (European Commission, 2009). Different stunning parameters can result in different effectiveness of stunning as well as different maintenance of narcosis. Objectives: Frequency of stunning current has never been studied under com mercial conditions, consequently the authors set this aim of the examinations. Materials and Methods: Measurements were performed in one abattoir, on 6 different days, on 193 pigs, in routine slaughter conditions for studying the effect of electrical frequency used for head-only electrical stunning. After stunning of pigs sequential animal based measurements were carried out right after stun ning, before and after bleeding in order to analyse how unconsciousness analge sia is achieved and maintained in relation to frequency. The effect of frequency on efficiency of stunning was evaluated by a score scale and on this basis the quality of analgesia was classified as efficient (proper), acceptable or inefficient. Results and Discussion: Statistical analysis of data showed, that frequency of the stunning current had significant role on effectiveness of stunning, but frequency had no effect on maintenance of narcosis. One-hundred-and-fifty Hz yielded effective stunning. However, higher than three hundred Hz is not rec ommended for stunning. This can be attributed to the fact that half waves of stunning DC lasted 3 milliseconds or less which period is shorter than the period needed for permanent depolarization in the neurons of the brain