A Do-it-yourself System for Scheduled Feeding of Laboratory Rodents in Their Home Cage

We're interested in modeling dieting paradigms and food insecurity in mice. Our research aims to titrate caloric supply to induce sustained weight loss. We aim to understand how the brain responds to varying degrees of weight loss to influence reproductive physiology and social behaviors. Acute fasting is sufficient to activate hunger signaling in the brain. We and others have recently shown that hunger signaling not only induces food seeking, but also induces other adaptive behaviors that promote survival during starvation. Our lab has worked to understand how hunger can influence reproductive physiology and social behaviors via specific neurons, circuits in the brain. Moving forward, we wanted to establish a better means of caloric restriction that better represents dieting patterns or models of food insecurity problems.

Our modular feeding system is inexpensive, readily available, and adaptable to standard cages used in vivariums. It's also advantageous because it provides a home cage setting for tethered, optogenetic, and fiber photometry experiments. Our feeding system provides a means to phase align food delivery and to course out food allotments over desired intervals. It's very common for caloric restriction protocols to administer food once a day, which does a poor job of mimicking human diets or food insecurity.

[Narrator] To begin, using a rotary tool with a 1.5-inch cutting wheel, cut out a 20x25-millimeter square into the microisolator cage lid. Position the opening 2.75 centimeters from the edge of the lid and ensure it is centered above the wire rack. Using a 3D printer, print a bracket to couple the auto feeder onto the cage lid. Snap the bracket onto the created hole. Then, slide the auto feeder onto the secured bracket. For timed experiments, set the feeding times first. Ensure that the auto feeder is fully charged. Then, press and hold the Settings button until the hour setting on the screen begins blinking. Next, use the up and down arrows to select the first desired scheduled feeding period and set the number of allotments for this time point. Load the auto feeder chambers with the desired food allotments, ensuring that each chamber contains no more than 1.5 grams of standard rodent chow. Label one chamber with tape or paint to monitor chamber rotation and confirm food delivery. To modify the cage system for tethered animals, laser-cut a three-millimeter thick clear acrylic piece. The insert is designed with tabs that snap into the cage top and features a center slit for patch cable passage. The 20x25 millimeter hole is for the auto feeder bracket, and 20 ventilation holes allow air circulation. Using a flat-head screwdriver or wedge tool, pry off the perforated top cover of the standard microisolator lid. Carefully release the tabs from the tab slots and remove both the perforated insert and the filter paper. Using a rotary tool with a 1.5-inch cutting wheel, remove the internal rib support grid beneath the perforated top and filter paper. After cutting, use a file to smooth the cut edges. Then, snap the replacement acrylic plate insert into the cage top. Begin by sliding the plate tabs into the tab slots along the short edges, followed by one of the long edges. Gently press until the plate snaps into place. To modify the cage for an external water bottle, drill an 11-millimeter diameter hole centered on the short edge of the cage 50 millimeters from the floor. On either side of the center hole, drill two additional six-millimeter diameter holes. Now, 3D-print an external water bottle bracket. Mount the bracket to the cage bottom using carriage bolts. Finally, fit a 50-milliliter conical tube with a sipper or stopper assembly into the external bracket.