What Does Mouse Poop Look Like? (Tips for Keeping Healthy Mice)
Light-brown stools in mice may be indicative of dietary imbalances or liver disease.
Why Does My Mouse Have Light Brown Stools?
“I just got a fancy mouse a couple of weeks ago. His name is Biscuit. Yesterday I noticed his poop was not dark brown but light brown. There are also piles of crumbs from his food in his cage (a repurposed aquarium). I think he is eating but can't tell for sure. Is he okay?” —Alexander
Liver Disease Can Cause Abnormal Stools
It is possible that it is just an odd diet that is causing the abnormal color, but the most common reason for any animal, including a mouse, to have light brown stools instead of the normal darker stools is a problem with the liver. It can also happen when the gall bladder is not working correctly and bile salts are not being added to the stool.
Causes of Liver Disease in Mice
- Parasites: Several different parasites cause liver damage in mice. (1) This is probably not going to be a problem for Biscuit as he looks like he came from an established breeding colony and has probably been dewormed.
- Virus: Mouse hepatitis virus, (2) viral hepatitis type A, influenza, and many other viral diseases cause liver damage in mice. The symptoms usually found include diarrhea, not just light brown stools.
- Bacteria: Several bacteria can cause liver disease, but you would probably also see other symptoms.
- Nutrition: If you are giving a commercial food, you can check the label and see if it is high in sugar or seed oils, which can affect the liver. (3) If you are feeding him free choice from the table, do not add sugar or processed foods, which may also alter liver function.
- Cancer: This is not something you should worry about since he appears young.
Most of the information available on liver disease in mice is just using them as models for human disease. If Biscuit is a young mouse, some of these diseases are not even going to be a problem. If he is young, as he appears, then the problem is more likely to be secondary to the diet.
How to Promote Liver Health in Mice
If you do not have an exotic veterinarian available or cannot take your mouse for any other reason, you can try alternative care by adjusting his diet and providing an exercise wheel.
Add Milk Thistle to His Diet
There are no doses available for using this alternative medication in mice, but if we extrapolate the dose we use in dogs, he would get 2 or 3 drops of this supplement on top of a piece of food. If he will not eat it, you can try the whole seed and can add three of the seeds to his regular diet each day. You should not need to order this more than once, as the liver should improve with the other steps listed.
Give Him Probiotics
In many species, we know that the GI microbiome (the normal healthy bacteria in the gut) is important in liver disease, and in mice, there is proof that healthy bacteria in the gut will prevent damage from some liver-toxic chemicals. (4)
There are not yet any probiotics available for pet mice, so I would recommend you use natural, unflavored, raw yogurt. Add a teaspoon next to his food each day to provide Lactobacillus organisms, but if he does not eat it within a few hours, you should remove it and decrease the amount the next day so that you can determine how much he will eat before it spoils.
Add Fresh Food to His Regular Diet
Many fresh foods contain antioxidants and vitamins that are not available or are only found in commercial diets at low levels. You can add a blackberry or raspberry to his food each day, and vary that with a strawberry, a slice of banana, or a piece of a carrot.
Make Sure He Has an Exercise Wheel
Obesity is related to liver disease in several species. Poor nutrition is one of the causes, but when mice do not have any means of exercise, they may also become obese.
When to See an Exotic Animal Vet
If you are worried that your mouse is not eating, the best thing to do is take him to an exotic animal veterinarian so he can be examined and his liver can be checked with bloodwork.
Unfortunately, mice are so tiny that only a little more than a quarter of a milliliter can be collected without hurting your pet, so you may want to call first and find out if they have experience with collecting blood in mice and have a lab that can determine values with micro-samples.
Sources
(1) Haque A, Best SE, Amante FH, Ammerdorffer A, de Labastida F, Pereira T, Ramm GA, Engwerda CR. High parasite burdens cause liver damage in mice following Plasmodium berghei ANKA infection independently of CD8(+) T cell-mediated immune pathology. Infect Immun. 2011 May;79(5):1882-8. doi: 10.1128/IAI.01210-10. Epub 2011 Feb 22. PMID: 21343349; PMCID: PMC3088131. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3088131/
(2) Bleau C, Filliol A, Samson M, Lamontagne L. Mouse Hepatitis Virus Infection Induces a Toll-Like Receptor 2-Dependent Activation of Inflammatory Functions in Liver Sinusoidal Endothelial Cells during Acute Hepatitis. J Virol. 2016 Sep 29;90(20):9096-113. doi: 10.1128/JVI.01069-16. PMID: 27489277; PMCID: PMC5044860. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2593347/
(3) National Research Council (US) Subcommittee on Laboratory Animal Nutrition. Nutrient Requirements of Laboratory Animals: Fourth Revised Edition, 1995. Washington (DC): National Academies Press (US); 1995. 3, Nutrient Requirements of the Mouse. Available from: https://www.ncbi.nlm.nih.gov/books/NBK231918/
(4) Mazagova M, Wang L, Anfora AT, Wissmueller M, Lesley SA, Miyamoto Y, Eckmann L, Dhungana S, Pathmasiri W, Sumner S, Westwater C, Brenner DA, Schnabl B. Commensal microbiota is hepatoprotective and prevents liver fibrosis in mice. FASEB J. 2015 Mar;29(3):1043-55. doi: 10.1096/fj.14-259515. Epub 2014 Dec 2. PMID: 25466902; PMCID: PMC4422368. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4422368/
This article is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from your veterinarian. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.
© 2023 Mark dos Anjos, DVM
