by Debbie “The Rat Lady” Ducommun
Rats have nutritional requirements that are very different from dogs or cats, and are more similar to that of humans. But rats still need a diet specially formulated for them. Please note that I do not believe “Sue Bee’s Rat Diet” advertised on the internet is a nutritionally complete diet for rats. If you want to give your rats a homemade diet, please see my recipe below.
When buying a commercial diet for your rats, I recommend one that has at least 18% protein for growing rats, and I don’t think 23% protein is too much for growing rats. Female rats tend to reach most of their physical growth at 6 months, but probably are not completely physically mature until 8 months of age, and male rats reach most of their adult growth at 8 months, but probably do not reach full physical maturity until one year of age.
Please note that Oxbow has two different rat formulas, one for adult rats and one for mice and young rats. Unless they’ve changed it, the label on the adult formula says it’s okay to give it to rats over 4 months of age, but I do not agree. I think the Oxbow adult formula should not be given to rats who are still growing. (Females stop growing about 6-8 months, and males 8-10 months.) And I personally would not give unspayed females the Oxbow adult diet, because a diet higher in soybean meal helps to prevent mammary tumors. The Mouse & Young Rat formula is definitely higher in soybean meal than the adult formula, however, the first ingredient is corn, so it may not be as good as a brand that has soybean meal as the first ingredient, such as Mazuri rat blocks.
Like most animals, rats can make all the vitamin C they need inside their body. Guinea pigs and primates are the only mammals that must get their vitamin C from food. But extra vitamin C might be good for rats. It’s a myth that rats must eat hard foods to keep their teeth from overgrowing. Healthy rats grind their teeth together to keep them the proper length and sharpness.
Rats have a flap in their stomach that covers the esophagus and prevents both vomiting and burping. For this reason, wild rats are very hesitant to try a new food in case it's poisonous. They nibble a little bit and wait; if they feel sick they associate it with the taste of the last new food they tried and avoid it in the future. This behavior is very adaptive for an animal that will try to eat almost anything, but who can’t vomit up bad food. Domestic rats aren’t quite as wary of new foods and soon learn to try any foods you offer them.
A Nutritious Diet
Rats, like people, are omnivorous which means they eat both plants and animals. Wild rats eat nuts, seeds, grains, vegetables, fruits, insects, worms, eggs, dead animals, and even frogs, fish, reptiles, birds and mammals that they catch and kill. This means they are partially predatory and have a high requirement for some nutrients that are most abundant from animal sources. This predatory nature is why rats are so smart! Rats do not need a salt lick. They get all the salt they need from their diet. Salt licks are only needed by strict herbivores.
The generic “rodent mixes” containing grains and seeds sold in bulk in pet shops do not even come close to providing all the nutrition rats need. Packaged mixes which are fortified with vitamins and minerals are better, but often rats will only eat their favorite pieces. Rat blocks specially made for rats are a complete diet. Soy products help prevent mammary tumors and decrease pain perception so I recommend rats blocks that have soybean meal as one of the first three ingredients for unspayed female rats. The soybean meal is not as beneficial for male rats, and it looks like now that low-protein blocks (14% protein) are better for older males.
Even though rats blocks are a complete food, they are processed, and I believe fresh foods are important. If you feed your rats blocks, or a fortified mix, they should be 80% of their diet and fresh fruits and vegies the other 20%. If rat blocks are your rat’s basic diet they should be given free-choice. I recommend offering the blocks in the Lixit FoodHopper.
Feeding healthy treats to your rats can help create a stronger bond between you. But if you give your rats a treat every time you see him, they might start grabbing your fingers even if you don’t have food. Tell your rats when you have food by saying “treat” first. That way they will know when you have food, and when you just want to play. Junk food is as bad for rats as it is for people. Rats who eat a proper diet and stay slim are healthier and live longer. Check the labels on commercial treats and avoid those that contain sugar and fat.
There is evidence that environmental color can influence metabolism and weight in rodents. A high school science project found that when mouse cages were surrounded with yellow paper, the mice ate more but lost weight, while when surrounded with blue paper they ate less but gained weight. Try decorating your rat room with lots of yellow!
Generally, if you would eat a food, you can give it to your
rats. Here are some exceptions and notables:
citrus juice—forbidden for male rats only, d-limonene in the skin oil, which gets into the orange juice during squeezing, can cause kidney damage and kidney cancer due to a protein that only male rats have in their kidneys. Pieces of the orange fruit are okay if you wash the orange-skin oil off of it after peeling it.raw dry beans or peanuts—contains antinutrients that destroy vitamin A and enzymes needed to digest protein and starches, and causes red blood cells to clump. Roasted peanuts are fine.
green bananas—inhibits starch-digesting enzymes
green potato skin and eyes—contain solanine, a toxin
mango—forbidden for male rats only, because it contains d-limonene. See above.
poppy seeds—contains a hallucinogen that can cause neurological damage.
raw sweet potato—contains an inhibitor
that blocks the action of trypsin, an enzyme that
digests proteins. Canned sweet potato is cooked and is fine
raw bulk tofu—can contain bacteria; packaged raw tofu is safe
wild insects—can carry internal parasites and diseases
Foods to Feed with Caution
can’t burp, and although they can fart, a large number of bubbles would
be uncomfortable going all through the digestive tract.
Dried corn can contain high levels of fungal contaminates which has been shown to cause liver cancer in rats. Corn also contains high levels of both nitrates and amines. These two compounds can combine in the stomach to form nitrosamines which are carcinogenic. Other foods high in nitrates include beets, celery, eggplant, lettuce, cucumber, radishes, spinach, collards and turnip greens. Therefore, I suggest you limit the amount of these foods in your rat’s diet. Some fresh corn is fine, but if you feed your rats blocks, it might be best to avoid brands which have corn as the first ingredient, if possible.
Spoiled or moldy food can contain deadly toxins. Never give nuts, grains, vegies or other food that looks or smells odd or spoiled. Don’t buy too much food ahead. Molds can grow even in sealed plastic bags. When cutting up veggies, cut off the dried part that has been exposed from previous cutting and throw it away. If you see mold growing on a food, throw the whole thing away. Do not attempt to cut away the moldy section. Invisible mold filaments penetrate deep into the food.
Pesticides on Produce
The Environmental Working Group compiled the following information from FDA and EPA data.
On average, rinsing with water will remove about one third of surface pesticides. Using soap, scrubbing, or peeling will further reduce the pesticide levels. Many pesticides, however, are absorbed by the plant or penetrate the surface of the fruit or vegetable. Where peeling is feasible, such as with apples and peaches, you end up throwing out some of the nutrients with the peel (although rats tend not to eat the peel anyway.)
In the US, the produce with the most and most toxic pesticides are: strawberries, bell peppers, spinach, cherries, peaches, cantaloupe grown in Mexico, celery, apples, apricots, green beans, grapes grown in Chile, and cucumbers.
To avoid pesticides, it’s a good idea to avoid these commercially
grown foods, or at least limit them in your rat’s (and your) diet. Buy
organic versions instead. To avoid foreign cantaloupe and grapes, only buy
these items from May-December when they are in season here in the
If you are feeding your rats my homemade rat diet, in the winter and spring buy watermelon instead of cantaloupe, or give another type of fruit, and give raisins instead of grapes.
The produce with the least pesticides are: avocados, corn, onions, sweet potatoes, cauliflower, Brussels sprouts, grapes grown in the US, bananas, plums, green onions, watermelon, and broccoli.
One source of toxins that’s often overlooked is tap water. If your tap water is fluoridated, DO NOT give it to your rats! Fluoride can cause brain damage in rats. Instead give them bottled water, but investigate the quality of the brand you choose. Some bottled waters are nothing more than tap water and some contain fluoride! Chlorine is also toxic (there is evidence that chlorinated water raises the risk of miscarriage in women in the first trimester!) If your tap water is chlorinated, buy a filter that removes chlorine (such as Britta or Pur) and only give your rats filtered water.
Even if your tap water comes from a well, lead leaches into the water from some pipes and all faucets. To reduce the amount of lead, run the water for a while, preferable until it becomes cold, which means it’s coming straight from the well, before filling your rats’ water bottles. Never use hot water from the tap for cooking or drinking because hot water contains more lead.
It’s a good idea to clean the water bottle out with a bottle brush every few days. Use a tiny brush or cotton swab to clean the sipper tube. You should also keep track of the level in the bottle so you can make sure your rats are getting water. Sometimes, the ball bearing in the sipper tube gets stuck and blocks the flow of water. I like glass water bottles better than plastic ones because some plastics can leach into the water. Hard plastic bottles are better than soft ones.
Low Sodium Diet
For certain health problems, notably congestive heart failure, a low sodium diet will be beneficial. The best low sodium diet is rat blocks. Fresh fruits and vegies are okay, but don’t give any canned foods. Check the label on frozen foods and only use those that do not list salt as an ingredient. Don’t give any dairy products, baked goods, processed cereals or foods, or salted foods. Give distilled water only.
Foods with Some Special Properties
These foods help to prevent strokes! Recommended for older rats or those with a family history of strokes: celery, prunes, parsley, oranges (no orange juice for males).
These foods have some antibiotic properties: banana, prunes/plums, garlic, tea, eggplant, raspberries, onion, mustard.
These foods may have some anti-virus properties: cranberries, prunes/plums, strawberries, onion.
These foods are good for arthritis: clove, dates, ginger, garlic.
Debbie’s Homemade Rat Diet
This is the most recent version of my homemade diet. Please note that there are some supplements that have been added since I first published it.
I worked hard to formulate this homemade diet, using a nutrition computer program, to make sure it meets the requirements set for rats by the National Research Council. Because my diet contains only fresh foods I feel that it’s the best diet for rats. If you wish, you can also feed a mix of my homemade diet and blocks. Even if you don’t want to make the whole diet, it will give you ideas for the best fruits and veggies to supplement your rats’ commercial diet.
All the foods in this diet contain valuable nutrients or cancer-prevention compounds, or both! Each rat has his or her own preferences, and not every rat will like every food in this diet at first. However, you must follow the diet closely for it to be balanced (see menu note). Most rats will eventually come to like most foods if they are given enough time. If your rat doesn’t like raw vegies, you can cook them lightly. The beans and sweet potato must be cooked. Purple grapes have more cancer-prevention phytochemicals than green grapes.
You might have to buy some of the ingredients for the molasses mix at a health food store. You can use any type of cooked dry beans (such as pinto beans) in the diet (canned is fine). Give a variety of different beans to take advantage of their different nutrients. My rats love garbanzo beans.
You can use canned or fresh sweet potato (yams) cooked in the microwave. You can also microwave pre-sliced liver; you don’t need to add oil. Then cut the liver into serving sizes and freeze individually. Or you can offer freeze-dried liver. You can also freeze oysters spread on a cookie sheet, then store in a container. Frozen foods are as nutritious as fresh as long as you use them before they get “freezer burn,” so you can use frozen fruits, beans, vegies, etc.
My homemade diet is not vegetarian, because rats are not naturally vegetarian, and I believe a diet is most healthy when it most closely matches an animal’s natural diet. However, if you feel strongly that you want to feed your rats a vegetarian diet, you must add 5 mg of copper (for example, as copper sulfate) to the molasses mix for adults. For babies, you must add 10 mg of copper.
This diet contains approximately 20% protein and 8% fat by calories, and about 3% fiber by weight.
Amount to Feed
The serving sizes listed are for a 1-lb. rat. If your rat is smaller or larger, you should adjust the portions accordingly. This diet is for adult rats. For babies offer adult portions and let them eat as much as they want. Babies need additional amounts of either liver or oysters, as they have a higher requirement for copper, and these are the main sources. Give them the liver or oysters four times a week until they are 4-6 months old.
Rat Diet Recipe
all foods raw unless otherwise indicated
(t=teaspoon, T=tablespoon, g=gram, mg=milligram, mcg=microgram)
about 3 T molasses mix (see recipe)
one serving of fruit (see menu)
2-3 servings of vegetables (see menu)
Twice a week (see menu)
1 serving cooked beef liver (organic is best) or canned oysters
Fruit: about half the size of their head
Veggies, beans: about the size of their head
Liver, oysters: about the size of their head
Recipe for Molasses
(will last two rats about a week depending on size--for more than two rats, you can multiply the recipe)
1500 mg calcium from chewable tablets or liquid calcium with vitamin D
2000 mcg chromium picolinate (yes, 2000 mcg is correct, the dose is based on their metabolism, not their weight)
250 mcg vitamin B12
15 mg manganese
3/4 C Total cereal
1 lb packaged (not bulk) soft tofu
4 t shelled raw sunflower seeds
1 T flax seeds
3 T raw rolled oats
4 t pearled barley
4 t millet
3 T cooked brown rice
4 T toasted wheat germ
2 1/4 T nutritional yeast flakes (5.6 g)
2 T blackstrap (dark or full flavor) molasses
Soak the tablets in a tiny bit of water and when soft, crush. Coarsely crush the Total in a plastic bag. Mash the tofu in a bowl. Add all ingredients together with warm molasses and mix thoroughly. Store covered in the refrigerator or freezer.
The oysters or liver, beans, sweet potato, brocolli, kale, and bok choy are required. (If bok choy isn’t available, substitute brocolli or collard greens.) The other vegies and fruits can be substituted with others if you like.
Mon Tues Wed Thurs Fri Sat Sun
berries banana grape/raisin melon prune/plum banana apple
kale broccoli bok choy broccoli kale broccoli bok choy
sprouts tomato parsley corn squash peas carrot
beans sweet potato beans liver/oysters beans sweet potato liver/oysters
For Outside the
I’ve been informed that Total cereal may not be available outside the
Suggested Additional Treats
If your rat eats all the regular diet and is still hungry you can give them any healthy table scraps available. A wide variety of foods is recommended in a healthy diet. Cooked bones of all types (even poultry bones) are great treats for rats, but be sure you have at least one for each rat because they will fight over them! Another occasional treat relished by rats are nuts in the shell. Chewing into Brazil nuts and hazelnuts gives them a particularly good workout!
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