Nest Building as an Indicator of Health and Welfare in Laboratory Mice

The overall goal of the following experiment is to observe the effect of an experimental treatment on nest building behavior in mice. This is achieved by providing the mice with nesting material in order to ensure they have a substrate to exhibit the behavior. As a second step, the animals are allowed to interact with the material which may result in the building of a nest.

Next, the nest is scored in order to assess its quality and complexity. Results are obtained that show the effect of various interventions based on the quality and complexity of the nest. The main advantage of this technique over existing methods, such as simple observation, is that the tests utilize highly motivated natural behaviors in mice which are easily observed, cage side when the mice are inactive.

Though this method can provide insight into basic aspects of mouse behavior. It can potentially be applied to other systems such as the evaluation of mouse welfare or derangement caused by neurologic or infectious disease. Generally, individuals new to this method will struggle because attempting to score a nest without a template will yield variable data To begin, weigh out eight to 10 grams of nesting material.

Crinkled paper is recommended for the best nest building results, but other materials can be used. Next, identify the cages to be scored at any convenient time. For the researcher or animal care staff, place the paper nesting material into the cage.

The material can be placed on top or mixed into the bedding to examine a wider behavioral repertoire. Return the next day, seven to nine hours after lights on to score the nests at a time when the mice will be less active. Using the nest scoring guidelines, score each nest on a scale from zero to five.

First, determine whether the material has been manipulated by the mice. This includes being processed or moved around the cage. If the material is untouched, the whole nest receives a score of zero.

Next, determine if the majority of the nesting material has been gathered to a central Nest site. If there is no clear nest site and the material has been manipulated, the cage receives a score of one. If a centralized nest site is present, consider the nest as if it were a square.

Each of the four sides of the square can be given a separate score from two to five. The four scores are then averaged for the cage nest score. A nest receives a score of two when it is flat with no shallow walls.

If the nest has a slightly cupped shape where the wall is less than half the height of a dome, it is given a three. A score of four is given. When the wall is half the height of the dome walls that are taller than half the height of a dome, which may or may not fully enclos the nest are given a score of five.

Alternatively, scoring can occur three to four days after the provision of new material. When peak scores are often reached for the time to integrate into nest test or tint, cut a two inch square of cotton nesting material into quarters. To obtain four one inch testing squares.

Test the animals within the first three hours of the light cycle to take advantage of increased nest building behaviors prior to daytime inactivity. When ready, open the cage lid and place one testing square on the opposite side of the cage from the main nest site. The test material should be placed in the same location each time the test is conducted.

Place the test square where it can be seen from outside the cage. Return to the cage after 10 minutes to make observations. If the test square is missing from its original location, the cage's tin positive.

If the test square remains in the original location, the cage's tin negative and additional observations may be needed to determine if the mice require veterinary attention. In this example, nest building was scored in cages held at three different ambient temperatures as the temperature increased the nest score, decreased nest shape can identify groups of male mice with a high level of aggression, which can result in wounding. Over a five week experiment, nest score was found to negatively correlate with the average number of wounded C 57 black six male mice.

This data shows that a painful surgical procedure can alter nest building behavior. The number of animals with a negative tint increased by approximately 60%after a painful surgery, but mice return to positive baseline levels three days postoperatively While attempting this procedure. It's important to remember that while the scoring method has been shown to have high inter and interrater reliability, that variability in scoring can affect your outcomes.

So be sure to properly train and assess the variability of your scores prior to starting your experiment, Following the procedure. Other methods, like direct observation or behavioral tests, can be performed in order to answer additional questions about the health and welfare or behavioral deficits of mice. After watching this video, you should have a good understanding of how to divide a nest into quadrants, how to score a nest, and how to administer the time to integrate to nest test.