Recommended techniques for handling lab mice to reduce anxiety

Improving handling techniques for laboratory mice helps reduce stress and anxiety, according to a study published today in the journal Nature Methods. The techniques identified in the study should lead to further improvements in the welfare of the mice.

Improving welfare conditions is a key element of the 'refinement' of laboratory procedures, one of the '3Rs' that aims to replace, reduce and refine the use of animals in experiments.

Currently, the standard procedure for handling mice is to pick up the mouse by its tail. However, scientists have not been aware that this can cause anxiety and stress to the mouse as mice appear to have an innate aversion to tail handling. Professor Jane Hurst and Rebecca West from the University of Liverpool have identified two other handling methods that significantly reduce anxiety and stress.

To assess anxiety-related behaviour in anticipation of handling, the researchers observed behaviour such as whether the mouse would voluntarily approach and interact with the handler immediately before and after daily handling, as well as urination and defecation during handling and a standard test of anxiety.

The first method involved bringing a clear acrylic tunnel towards the mouse. The mouse would voluntarily walk into the tunnel, allowing it to be lifted without direct contact.

The second method was for the handler to cup the mouse in his or her hands and allow it to walk freely over the open gloved hands. As unfamiliar mice tend to jump immediately away, Professor Hurst recommends closing the hands loosely around the mouse on the first time until it becomes accustomed to the experience.

The researchers also found that restraining a mouse by its tail did not cause undue stress or anxiety if the mouse had first been picked up using one of the above methods. When the mouse needed to be restrained more securely by the scruff of the neck, this did not reverse the taming effects of being handled on the open hands or using a tunnel.

"Animal welfare standards in UK laboratories are extremely high, but even so, it is very important that we always look for ways to improve conditions for the animals," says Professor Hurst. "The routine handling of laboratory animals is essential, so it is important that we do all we can to reduce any stress and anxiety. Using methods that minimise anxiety also reduces confounding factors and improves the responses during experiments, leading to more robust scientific outcomes."

The research was funded by the BBSRC, NC3Rs and the Wellcome Trust.

Dr Vicky Robinson, Chief Executive of the NC3Rs, comments: "This study shows that even the simple act of handling a mouse can cause it anxiety and stress, which in turn can affect experimental results. All researchers using mice are going to have to ask themselves whether picking the animal up by its tail is now the right thing to do."

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