Operation of Powered Push Gates on CO2 Pig Stunners and Other Livestock Handling Equipment

by Temple Grandin
Dept. of Animal Science
Colorado State University

There have been questions on the proper use of powered push gates on CO2 stunning units. Below are recommendations on how to use these gates to move animals calmly and maintain a high level of animal welfare. This recommendation applies to all species and to any gate that is powered by a mechanical device run by hydraulics, pneumatics, or electric monitors.

  1. If the gate knocks over a single animal and causes it to fall, this is a welfare problem that requires corrective action. Falls caused by powered gatest are counted on the numerical scoring system. Over 1% fall is not acceptable. If the gate continues to cause multiple animals to fall in a single day, this is a serious animal welfare problem.

  2. Pigs and other animals that have fallen down must never be dragged or pushed along the floor by a powered gate. Dragging or shoving (scooting) a single fallen, downed, or non-ambulatory animal with a powered gate is a serious animal welfare problem. This is an act of abuse and would be an automatic failed audit or warrant regulatory action.

  3. In normal operations, powered gates will touch animals and may gently push on them. This is the normal use of a powered push gate.

  4. Animals should not be overcrowded with push gates. When animals are being moved with a powered gate, they must have an area to move into, such as an empty CO2 gondola, another pen or space at the end of an alley. Overcrowding is defined as crowding a pen so tightly that there is no space for the animals to move into. Overcrowding is poor handling but it is a much less serious welfare problem than a powered gate that causes multiple animals to fall or it drags/pushes a fallen or downed animal along the floor.

  5. ln some situations, powered gates work best and animal handling is smoother and calmer if movement of powered gates is controlled by a person continuously pushing a switch or other device that activates the gate. The gate will stop advancing towards the animals when the person stops pushing the switch or lets go of some other device used to advance the gate. Fully automated push gates that do not require a person to operate a switch work well in some situations. Fully automated gates are most likely to work well when the distance that the gate has to move the animals is short. A good example is the automated push gate that moves pigs into a CO2, gondola. For most pigs, a high level of welfare can be attained with a fully automated push gate. However, there are some pigs from certain farms that are so difficult to move that the gate may need to be converted to being controlled by a person. Fully automated push gates that move pigs or other animals longer distances are less likely to work well and converting them to a powered system operated by a person improves handling and reduces overcrowding.

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