Many rat owners find one diet and will swear that it is the best and only one to use. Availability of food and ingredients to make a mixed diet vary from place to place. Rats are pretty adaptable and will eat a wide variety of things. You simply need to construct a proper diet out of what is available. When feeding your rat, notice any weight loss or gain or the appearance of "protein sores," scabs on the neck and back males often get from too much protein in their diet, and make changes to the diet to compensate. Adult male rats need around 15% protein, females need around 20%, and hairless rats tend to need a slightly higher amount due to their high metabolisms. Fats should be kept to a minimum. Pregnant, lactating, and growing rats need more fat and protein (a few pieces of kitten chow every day is good). Here are some foods and food components you should or shouldn't use to make your rat diet.
Pelleted/Block/Cube Rat Food: Some brands include Critter Cubes, Oxbow Maintenance, LabDiet, and others. They look like large kibble and include everything your rats need. Many brands are expensive and hard to find, but others are quite reasonable. Laboratories use this diet, and it is healthy. Rats will eat this diet but enjoy some variety. This can be given as a complete diet.
Rat Food Mixes: Some brands include Kaytee, Vitakraft, 8 in 1, and Reggie Rat. These foods can also be expensive and hard to find. A mix is more appreciated by rats, but they may pick out what they don't like. Most mixes include alfalfa pellets which rats can't digest and won't eat. If you feed a mix, you should wait until your rats have eaten all but these pellets before giving them more food. This can also be given as a complete diet.
Hamster/Gerbil Food: Hamster foods include many things that are good for rats too, but this should not be the only thing you feed. Rats need more protein than hamsters. Hamster mixes are widely available and some brands are fairly cheap.
Rabbit Food: Rabbit, Chinchilla, and Guinea Pig food is not proper for rats. These animals are all strict herbivores and their diet includes fibers that rats cannot digest.
Bird Seed: A good addition to the diet in small amounts. Seeds are mostly fat, especially sunflower seeds. The fat helps keep fur glossy and can help bulk up growing or underweight animals. Use sparingly, even just as a daily treat. (Rats are very fond of sunflower seeds, so they make excellent treats for training or bonding.)
Cat Food: Protein and fat are far too high for rats, and high protein diets can cause obesity or even increased risk of cancer. Cat food can be given to pregnant or nursing rats who need higher energy.
Puppy/Kitten Food: Same as cat food.
Dog Food: Anything under 20 % protein can be used as part of the diet. Dog food can cause protein sores in male rats but females and young rats have no trouble with it as a major part of their diet.
Human Foods: The earliest pet rats probably lived on human food. Rats have similar dietary needs to people but living on table scraps alone isn't the best thing. Cereals and pasta are great additions to your rats' diet. Fresh vegetables are also good to give a couple times a week. Rats can eat most table scraps as a rare treat.
Bones: Very good to wear rat's teeth and they love them! Even poultry bones are safe for rats. Never give them raw, though. Avoid small bones and ones with sharp edges.
Treats: Most human food can be given as occasional treats. Rats also like commercial treats available for rodents or birds. Dog biscuits are fine too.
Some Rat Diets/Recipes:
Food to be Wary of:
Candy: Rats aren't at big risk for cavities, but candy can make them obese and speed onset of diabetes in those at risk for it.
Chocolate: It is a myth that chocolate is toxic to rats. It is fattening, and caffeine can cause problems.
Soda: Like chocolate, it is the sugar and caffeine you need to watch out for.
Alcohol: Same risks associated with people. Alcohol is a depressant and can cause liver damage.
Peanut Butter: Not bad for rats in itself, but if a rat eats a glob of it too quickly, he may choke.
Corn: Used as a filler in many foods, some rats are allergic to corn and will get sores (like protein allergies).
Citrus: Very acidic. Excess Vitamin C and orange oil (sometimes present in juice) can also cause problems.
Tomatoes: Like citrus, very acidic.
Spicy Foods: May be acidic and cause other problems.
Salty Foods: High sodium increases the risk of heart failure (like in humans). Sodium is a problem in most canned or processed human foods.
Bleu Cheese: Is toxic.
Peach Pits or other Fruit Seeds: Are toxic.
Licorice: Suspected to cause neurological poisoning.
Raw Beans or Nuts: Destroy Vitamin A and causes other problems.
Raw Sweet Potatoes: Form cyanide in the stomach.
Raw Brussel Sprouts: Destroy thiamin.
Raw Artichokes: Inhibit protein digestion.
Green Bananas: Inhibit starch digestion.
Green Potato Skins and Eyes: Contain a toxin.
Rhubarb: Contains high levels of oxalates.
Spoiled Food: Lots of problems. Don't feed rats anything you wouldn't eat yourself.