NCad advocates careful weighting of methods for identification and genetic characterization.

At the request of the Minister of Agriculture, Nature and Food Quality, the NCad has investigated whether it is possible to phase out the toe (pastern) cut as an identification method, provided that an alternative is possible. This was not the first time this has been investigated. As early as 2016, ZonMW made an inventory of the application of the toe clipping on behalf of the then Minister of Economic Affairs.

Why toe clipping and ear clipping?

In biomedical research, genetically modified mice are used to investigate functions and processes of the healthy and sick body. One or more genes are modified depending on the process to be investigated. The breeding of genetically modified mice aims to obtain more mice with a specific genetic modification. In cases where only part of the offspring of a single parent pair inherits the genetic modification, it is important to determine which puppies have the genetic modification and which do not. Therefore, a piece of tissue, a tissue sample, is taken from each pup at a young age from which the DNA is isolated. The DNA is then examined for the presence of the genetic modification. The result of the DNA test of a piece of tissue must be traceable one by one on the pup from which the tissue has been taken. In order to do that, the pup must be given a unique marker at tissue collection that is linked one-to-one to the tissue sample. Two methods are used for this in the breeding practice of genetically modified mice: the toe (pastern) cut and the ear cut. These methods are preferably performed well before the weaning age, so that the results of the DNA analysis before the weaning age are known.
At the toe (pastern) cut, in puppies the last pastern of 1 toe is cut from a maximum of two legs. The phalanx is used to isolate the DNA and by writing down on which pup which toes (maximum 2 of different legs) are cut off, the DNA result can be linked to the pup from which the tissue sample was collected. At the ear cut, a triangle or a circle is punched out of the ear. The punch is used to isolate the DNA and here too, by keeping track of which punch was taken from which ear and from which side of the ear, the DNA result can be linked to the correct pup. Multiple punches may be taken per mouse. In these interventions, two goals are thus achieved simultaneously, namely: the characterization and the unique and permanent identification of the animal.

Welfare damage cannot be scientifically substantiated.

The toe (pastern) cut and the ear cut are procedures in which body parts are injured and thus lead to a certain degree of well-being damage. However, there are no good indicators to estimate the degree of welfare damage to the toe and earcups, based on scientific evidence. There are also identification and characterization methods that do not injure the body, the non-invasive methods. With neither of these interventions, an animal can be characterized and identified at the same time, so at least two actions must be performed for characterization and identification. Another drawback is that none of the non-invasive identification methods gives a permanent identification and therefore has to be reapplied at some point. It is plausible that a combination of non-invasive methods causes less welfare damage than the invasive methods. The NCad has investigated whether other alternatives are available and eventually found that there are no alternatives available in Europe that make it possible to phase out the toe clipping.

Reassess per study design

The NCad recommends that, for each research design, a careful consideration is always made with regard to the choice of the most suitable identification and characterization methods in the current situation, whereby aspects must be taken into account of damage to integrity, damage to well-being and improvement of the quality of science.

Handy overview of existing methods and possible alternatives

The advice contains an overview of all existing methods for identification and characterization, as well as an explanation of alternatives. NCad member Jan-Bas Prins about this "it is a guide that is easy to consult for choosing the most suitable identification and characterization methods for a study."

Further research needed

The NCad advises the Ministry of Agriculture, Nature and Food Quality and the Ministry of Education, Culture and Science (OC&W) to put in place a concrete project with the assignment of combining to develop sustainable non-invasive identification and characterization techniques, whereby the integrity and welfare of the animal is not, or at least, affected.
And conduct further research into innovative techniques to identify animals and characterization, such as "individual facial recognition" and DNA isolation and analysis techniques. Attention should also be paid to the evaluation of the Animal Experiments Act to the impact on the welfare and integrity of laboratory animals from outdoor activities fall within the definition of animal testing, but are directly related to it.