Stunning and killing

Stunning an animal prior to killing renders it unconscious and insensible to pain by disrupting normal brain function. This benefits both animal welfare and human safety, particularly when dealing with large animals such as cattle. From a welfare perspective, it is very important that this loss in consciousness is immediate to prevent the animal experiencing discomfort or pain caused by the stunning method. The methods of stunning and killing described later in this guide include simple-stunning followed by a killing method, and stun-kill methods.

“Simple stunning” describes methods which render the animal unconscious and insensible to pain, but do not lead to death. Animals which have been stunned using a simple stunning method will eventually regain consciousness and recover.  If such a method is used, it must be followed as quickly as possible by a procedure that causes death. When using simple stunning methods (e.g. electronarcosis), an additional step is required to kill the animal. It is important to ascertain the length of time available to perform the kill before the animal recovers consciousness.

There are many definitions of “death”. For the purpose of this guide, death is considered to occur when the animal’s brain irreversibly ceases to function. The part of the brain responsible for regulating essential body functions such as breathing, heart activity and responses to pain is called the brainstem.  When the brain is starved of oxygen it can no longer function and the animal dies. This may be achieved by directly causing physical damage to the brainstem (e.g. by pithing) or disrupting the function of the heart (e.g. using electricity) to prevent oxygenated blood reaching the brain.

Some techniques, such as firearms or prolonged exposure to anoxic gas mixtures, are considered to be stun-kill methods. That is, they cause unconsciousness and lead to death without an additional action being taken.

Stunning and killing methods suitable for use on-farm during a disease outbreak are discussed later in this guide.

Next: Humane killing