This article is from the WSSF 2013 AFRMA Rat & Mouse Tales news-magazine.

By Karen Robbins

Yi Lu, Model Animal Research Center, Nanjing University, China
QI’m a Ph.D. student at Model Animal Research Center of Nanjing University. My current project requires 12-day-old to 18-day-old mice with empty stomach stats. I found that your colleagues have lots of experience about hand-raising orphan mice. So, can you give me some advice about appropriate fasting time that will not cause harm to these immature mice?

ATiny orphans are fed every 2 hours since that is how often mom would feed them—not sure if the stomachs are empty at that point. Once the eyes open around 12 days, then solid food can be added and they can go a little longer between feedings. Since the eyes are open at 12–18 days, then they would be eating more than just mom’s milk (also nibbling on food in the cage). I sent your question to our vet/pathologist Dr. Carmen Jane Booth, and this is her answer:

We never fast mice in research. Only sick mice that are close to death have empty stomachs in my experience. These mice are emaciated with no body fat reserves and die from dehydration and anorexia. Otherwise, the metabolic rate is so high in mice that you can’t empty the stomach without risking harm to the mouse. They do nurse frequently so the stomach is not really ever empty, and if it is, it is not for long. “I do a lot of pathology for post natal death in mice. We see pups die in less than 24 hrs when they do not nurse for any reason.

So, fasting for mice is not a good thing.