Head-Only Stunning

Head-only stunning can be carried out on individual animals within a group in a pen, or on individual animals in a restrainer-conveyor. There are two basic types of head-only tongs: scissor or fork (Figures 5 and 6). The site of application is the same in both cases but the method of restraint may be different. The most widely used are scissor tongs (Figure 5), which can be used in either group stunning pens or restrainer-conveyors. The arms are usually around 75cm long and have a maximum jaw gap of about 30cm; the handles may incorporate a switch. The design of the electrodes varies, but is generally either a parallel array of metal teeth, or a circular cup electrode with one or more central spikes. The electrodes are connected to insulated blocks at the ends of the tongs.

Figure 5 Scissor stunning tongs	Figure 6 Fork stunning tongs

To enable accurate placement and maintain contact, the fork tong (Figure 6) should only be used when stunning animals held in a restrainer. The electrodes are usually longer than those found on scissor tongs, to allow for variation in the size of animals, and are connected to a single handle by insulated arms.

Control equipment must be adequately protected from both physical and water damage. The easiest way to achieve this is to site the control box away from the stunning and sticking area. Provided the cable between the stunning tongs and the stunner control box is of sufficient diameter, there should be no appreciable drop in current level due to increased resistance caused by cable length. The operator must be able to see the meters which display the current and voltage, and be able to hear and see the audible and visible signals to warn if the stun duration falls below the required level. It is important that the operator has unrestricted access to the safety stop controls.

Head-only stunning electrodes should be placed so that they span the brain as directly as possible. Positioning the electrodes anywhere else means that more of the current may flow through lower resistance pathways and not entirely through the brain, thus reducing the effectiveness of the stun. When using scissor-type tongs on sheep and pigs, the recommended tong position is on either side of the head between the eye and ear (Figures 7, 8 and 9). In practice, this position can be difficult to achieve on pigs because of the shape of the head; so an alternative is just below the ears, or diagonally below one ear to above the opposite eye (Figures 10 and 11). When using a fork-type tong the position is the same, between the eye and ear on each side of the head. In both systems, once the electrodes are applied they must be kept in constant contact with the animal to prevent interruption to the stunning current flow, as this can lead to an ineffective stun and can also increase the occurrence of carcase damage.

Figure 7 Electrode position for sheep (front view)	Figure 8 Electrode position for sheep (side view)
Figure 9 Electrode position for pigs	Figure 10 Alternative electrode position for pigs
Figure 11 Diagonal electrode position for pigs

Next: Head-to-Back Stun-Kill