American Fancy Rat & Mouse Association

This article is from the WSSF 2008 AFRMA Rat & Mouse Tales news-magazine.

Beginners’ Corner

Fat Mice; Bruxing Mice
Fat Mice

Lynn Lehman, Racine, WI
Q I’m very glad I asked about what to feed to my little munchkins. I think they do sell blocks or pellets here at the pet store. I wonder if the Kaytee mix is what caused my poor “Cleo” and “Daisy” to become overweight? They were bought together 2½ years ago as little babies and became obese quickly, though they are very active and healthy. When people see them, they say, “Those can’t be mice, they’re hamsters!” None of the other mice are obese, thank goodness. I’m very surprised these two little chunks are still going strong at such an old age being so overweight.

Cleo is all black with black eyes and a tan belly, and she’s the bigger of the two. Daisy is a pretty color that I’m not quite sure what to call it, maybe a tan or gold with white bands and black eyes. They are cute ittle “pork chops,” but I worry that their health will not be so good because of their weight, though for their age and weight they get around very well!

I went to the pet store the other day and could only find a small 2 lb. bag of Kaytee Forti-diet for mice and rats. The feeding instructions say for 1 mouse, feed 1 block, for rats, 2–3 per rat. Does this sound suitable for them? I hope so, because that is all they have besides what I was feeding them. The directions also say to begin with a mixture of the “old and the new” foods, gradually increasing the amount of new food over a 7–10 day period. So, I have mixed just a very small amount of the old stuff with these blocks—I hope they will accept the blocks with no problems. I feel so bad changing their food, but I feel worse that I have unknowingly been giving them junk food all along.

A Your Cleo and Daisy sound like some of my mice. The Orange, Gold, and “yellow” colored mice are what we call “fat gene” mice. The gene causing their color is linked to a gene causing obesity, so these mice are always fat. There is nothing you can do about it. Even if you just about starve them, they will still be fat. Interestingly, some of my oldest mice have been these “fat gene” mice. They are prone to tumors, however, so be careful to limit the amount of fat in their diet.

I wouldn’t worry about their weight at all. At their age, it isn’t going to make the slightest difference anyway. My little fat ones never make it past 1½, so yours are doing great.

I’m glad to hear you found some lab blocks. I hope the critters are happy with them (or at least getting used to them). The Kaytee ones are better than most that are available at the pet shops. If you want, you can probably request that they order you a big bag (I think it’s a 25 pound bag). It sounds like a lot, but keeps well, particularly if you can put some of it in the freezer. [Some of the high quality lab blocks are available online and AFRMA sells the 8604 Teklad formula on our online Sales Catalog.]

I free feed the lab blocks to my mice and rats. I make small hanging boxes out of ½ inch x 1 inch wire mesh (rats) and ½ inch x ½ inch mesh for mice. I fill these with lab blocks and hang them in the cages. The rats and mice have to work for their food . . . biting off small pieces and working them through the wire. This gives them something to do all day and keeps the food clean and fresh. I refill the boxes as needed. This way you don’t have to worry about the critters getting enough to eat, and you don’t waste any. I have bought my rat feeders through the club in the past, but no one sells wire basket mouse feeders. You can buy mouse feeders in pet shops. They are sold by the Lixit Company and are plastic. They work well for mice, but do get chewed up eventually.

I don’t know the actual number of lab blocks my critters eat, but what you’re feeding sounds about right. Believe it or not, once your critters get used to eating blocks they will prefer them over many other items. Nichole Royer

Bruxing Mice

Editor, Karen Robbins
Q I had this comment made by a new mouse member—she says a couple of her mice brux—they come running out of their house and “brux” when they see her; she says they are not sick. Do mice brux like rats? Since when rats “brux” you can’t hear it very well, I would think if mice “brux,” you wouldn’t be able to hear anything unless you held them up to your ear. I have had mice that I would be checking their breathing and hear a whiffling sound and look at them and they are doing the chewing with their teeth, like a bruxing rat, while sitting on my hand. Also, rats “brux” when they are relaxed/being petted, not running around so wouldn’t this be the same with mice? Could she be confusing rattling with bruxing?

Update: I have seen the mice and they were rattling.

A I could not find anything in the published literature regarding this. Biologically, rodents have teeth that continually grow throughout their life. Because of this they must be continually worn down. This serves them well with gnawing hard grains and gaining access in a natural environment. Thus, in a caged environment, they can either grind their teeth on their food, the caging, objects in the cage, or just grind them at will. My personal experience is that mice like rats have to grind their teeth. I have heard mice do this. I have never encountered a situation when a mouse would grind their teeth while moving. My experience has been that they do this while relatively stationary. I agree with Karen that pet mice are probably just the same as pet rats with this. Carmen Jane Booth, D.V.M., Ph.D. *

Back to top

Updated March 7, 2014