Killing methods

Killing with a rotor

Killing with a rotor involves placing the mink one at a time into separate compartments. When the mink is placed in the compartment, the rotor turns so that the compartment fills with carbon dioxide. The next mink is placed in another compartment and the rotor turns again. This continues until all the compartments are full. The disadvantage of the rotor is that there is not room for as many mink as in the case of a killing box, which makes the rotor less efficient in terms of time. The handling of the rotor makes this still more time-consuming. The big advantage of the rotor is that every mink is killed individually in a separate compartment, which means that the mink do not need to be confronted with other mink. Killing takes place quickly and is easy to monitor. When killing is complete, the mink can be picked out separately. This permits good monitoring to ensure that the mink have died.

Photos not available at the moment!
Rotor for killing mink. The mink are placed one at a time into the compartments, which are then filled with gas. Good monitoring of the mink is possible. Photograph: SLU.

Killing mink in the case of injury and disease

Killing in the case of injury and disease differs fromkilling in connection with pelting. In the case of injury and disease, one individual at a time is generally killed. If the number of individuals need to be killed at the same time, this is done in the same way as described for killing in connection with pelting. Injured or sick animals are killed using a device suitable for one mink. There are a number of models designed as either a tube or a box in which the mink is placed. Larger boxes are also available in which the mink can be placed when it is still in the trap. This device is normally connected to a small gas cylinder. The smaller space in the device for individual killing limits the movements of the mink and allows the gas to be pumped in very quickly, which reduces the risk of unnecessary suffering. The same is true of a small box. Smaller devices are also very easy to carry on the feed truck, for example. If the device is stationary, the mink must be transported to it using a trap or transport cage.
Photos not available at the moment!
Individual killing device for mink, stationary model designed as a box in which the mink is placed. Photograph: SLU.

Use of gas other than carbon dioxide

Carbon dioxide is the gas permitted for killing in Sweden. Nitrogen and carbon monoxide are used in other European countries, and noble gases have also been studied on mink and other animals. The animals do not detect these gases in the same way as they do not irritate the airways. Tests have also been carried out in which the carbon dioxide has been mixed with other gases, which makes it possible to reduce the carbon dioxide concentration. In some cases, it has been seen that such mixtures can shorten the stunning process when stunning other farm animals. The problem with other gases is that they are more expensive and more difficult to handle in purely practical terms. Carbon dioxide is the only gas that is heavier than air. Carbon dioxide is also hazardous for stockmen to handle as low concentrations cause injury. Carbon monoxide is also odourless and causes no irritation, which makes it difficult to detect. Due to its toxicity, carbon monoxide is no longer permitted (although it used to be permitted for chinchillas) for use for killing fur-bearing animals in Sweden.
The video sequences below show examples from a study in which the reactions of pigs to low concentrations of carbon dioxide and argon respectively were compared. The pig showed clear signs of discomfort and moved away from the carbon dioxide, while they continued eating and were apparently unconcerned about argon. In the lower video, we can also see that the pig returns to its food and is exposed to argon again after having lost its balance and fallen over – in other words, it has not realised that there is something in the air that is causing problems.

No video avalable at the moment!

The video shows how the pig reacts to CO2 When it is offered food. Photograph: Dr. Raj, University of Bristol.

No video avalable at the moment!
This video shows how a pig reacts to argon when it is offered food. Photograph: Dr. Raj, University of Bristol.

However, studies involving rats have been carried out in which the rats showed discomfort when they were exposed to argon. When mink were exposed to argon, they did not try to escape it immediately but remained in the space for 23 seconds. The fact that they moved away after 23 seconds when the space was filled with argon was probably due to the fact that they detected the lack of oxygen but did not experience any discomfort from the gas as such. No studies into how chinchillas react to argon have been carried out as things stand at present.