The design of pig stunning tong electrodes-A review.

The effectiveness of current electrical stunning systems for pigs is discussed and the need for improvements in the design and construction of stunning tongs and electrodes are explored. A review of existing stunning tong electrodes for use with free standing or restrained pig is discussed. The potential problems with existing systems are highlighted as: (1) the profile of the pigs head precludes the application of existing electrodes in the correct position; (2) the small area of contact enhances carbon build-up which increases electrical impedance; (3) the electrodes are easily tarnished with few cleaning tools provided. Good tong positions that span the brain are described as between the eye and ear on each side of the head, below the ear on each side of the head or, diagonal application between the top and bottom of the head. The notional contact impedance is the major component of resistance to current flow within the stunning system. The proposed use of different electrode designs and constructional material is investigated. The effect of the introduction of the fail-safe device would be to heighten the interest in contact impedance within the plant and that could ensure that the investigation of different electrodes is explored at least at plant level.