Average cortisol levels for commercial cattle slaughter with captive bolt stunning.

Recommended Captive Bolt Stunning Techniques
Safety Tips for Workers

  1. Cartridge-fired stunners must ALWAYS be uncocked before they are set down.

  2. NEVER, NEVER throw a cartridge-fired stunner to another person.

  3. Inspect latches on stunning boxes to make sure they latch securely. Before the next animal is admitted to the box, check the latch.

  4. All guards must be kept in place over exposed pinch points which could be easily touched by employees during normal operation of the restrainer system equipment.

  5. If a worker has to get inside a restrainer conveyor system to unjam it, lock it out first to prevent somebody else from turning it on.

  6. Cartridge-fired stunners must always be kept unloaded when they are carried away from the stunning area.

  7. Good maintenance is essential on pneumatic stunners to prevent excessive recoil which can strain and injure the operators hands, arms or back.

  • To produce instantaneous unconsciousness, the bolt must penetrate the brain with a high concussive impact. For cattle, the stunner is placed on the middle of the forehead on an "X" formed between the eyes and the base of the horns. Some plants which save brains, place the stunner on the hollow behind the animal's poll on the back of the head. This position is less effective, therefore the frontal position on the forehead is recommended.

  • A good stunner operator learns not to chase the animal's head. Take the time and aim for one good shot. The stunner must be placed squarely on the animal's head. All equipment manufacturers' recommendations and instructions must be followed. Pneumatic stunners must have an adequate air supply. Low air pressure is one cause of poor stunning.

  • Poor maintenance of captive bolt stunners is a major cause of bad stunning. Pneumatic captive bolt stunners require cleaning and seal replacement every night in large plants. For example, a cattle plant which is double shifted and has a chain speed of 250 head per hour will require two to three pneumatic stunners to be completely serviced every night. It is important to keep stunner cartridges dry and the correct cartridge strength must be used.

  • Eye reflexes should be checked often to insure that stunning is making the cattle unconscious. When the eyelid or cornea is touched there should be no response. An animal that blinks is not properly stunned. Breathing should have stopped and there should be no indication of a righting reflex when the animal is hanging on the rail. Reflexes may cause a stunned animal's legs to move, but the head should hang straight down and be limp.
    When slaughtering is done carefully cortisol levels in cattle can be substantially lower than farm handling conditions. Tume and Shaw (1992) reported that steers and heifers slaughtered in a small research abattoir had and average cortisol levels of only 15 (ng ml)-1, and cattle slaughtered in a commercial slaughter plant had levels similar to farm handling.

    Beta-endorphin levels, which is another indicator of stress, were not significantly different between the two groups.

    For commercial cattle slaughter with a captive bolt stunning the following average values have been recorded:

    When things go wrong the stress levels increase greatly. Cockram and Corley (1991) reported a median value of 63(ng ml)-1. One animal had a high of 162(ng ml)-1. The slaughter plant observed by Cockram and Corley (1991) had a poorly designed forcing pen and slick floors. About 38% of the cattle slipped after exiting the holding pens and 28% slipped just before entering the race. Cortisol levels also increased when delays increased waiting time in the single file race. This was the only study where vocalizations shortly before stunning were not correlated with cortisol levels. This can probably be partly explained by earlier stress caused by the slick floors. Ewbank et al.,(1992) reported the lowest average value. This may be explained by excellent handling before the stunning box.