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UCSD Mouse Time–Controlled Feeding Cage

The Executive Summary can be found here: Executive Summary

Background:

The purpose of this project was to design an automated mouse feeder that can cut off the supply of food to the mice. There have been recent scientific studies that have shown that the time one eats can affect one’s health just as much as the quality of what one eats. For instance, it is well known that regularly eating at night leads to insulin resistance and can cause obesity. This is most likely due to disturbances in the normal circadian rhythm. However, this phenomenon is not fully understood and more scientific research is needed.

The sponsor of this project, Dr. Nicholas Webster, performs time-restricted feeding experiments on mice. He has shown that limiting access to food for anywhere between 4 and 16 hours over a period of one to four months leads to weight loss and improved health in the mice. Now he wants to expand his experiments to examine the effects of dietary restrictions on breast cancer growth. In the past, the food supply was manually adjusted by a steady stream of undergraduates working in the lab. This required a lot of person-hours and was somewhat impractical for long-term studies.

There are current commercial systems that provide controlled food and water access. These systems also monitor mouse activity, food and water intake, and a few other measurements. Consequently, these systems are very expensive. Dr. Webster was quoted $56,500 and $99,000 for a cage system from Sable Systems and Research Diets BioDAQ respectively.

The goal of this project was to create a relatively inexpensive automated feeder. It was important to have a simple user-interface that could program multiple cages at once. In addition, the feeder had to be easily removable so that the cage could go through cleaning in an autoclave oven.

Objectives:

• The primary objective is to build a time-controlled mouse feeder that is able to both cut off and provide food supply to mice at setting time.

• The secondary objective is to make sure that the mice get fully accessibility to the food at feeding time.

• The third objective is to create a sensing system that is able to track the food consumption.

• Create a simple user-interface for programming feeding cycles of multiple cages at once by LabVIEW.

• Make the feeder easily detachable from the cage for cleaning purpose.

Final Design

In the final design, the feeder was designed to hang on the back of the cage due to the space constrain inside the mouse cage. The back of the cage was cut for the grating to be mounted in. The gratings on both the cage and the hopper are made of thin and strong fishing wire, that optimizes the thickness between the gratings at feeding time and assures the mice can get accessibility to the food. The hopper was screwed on the buffer that was screwed on top of a 100 gram load cell. The motor and the load cell were mounted to another buffer that connects with the rail of the slider. LabVIEW sends the command, and then the motor drives the hopper toward the grating of the cage when it is time to feed and drives the hopper back to rear of the feeder when it is time to cut off the food.

CAD Model the Design

Performance Result:

The users only need to set up the food providing and cut off times in the LabVIEW interface for the automated feeding system to work. When the motor is initiated, it will keep running for 3 seconds and then stop. The system will automatically record the weight of the food sent by the load cell each time after the hopper moves backward to position from the feeding mode. The LabVIEW interface is shown below.

In the testing, the mouse was able to reach the food when the hopper was in the feeding position. The picture and video below show a mouse reaching through the grating and eating the food pellets.