Rats are an omnivore species, and, like us, have adapted to be able to survive on a huge variety of different foods. A rat's sense of taste is supposedly comparable with ours, which, if true, gives you an idea about how they view food.

Most pet shops will sell bags of commercial rat feed, but a lot of these are actually pretty poor, and not the best option for a rat, long term. Many of them use cheap ingredients, or else they are riddled with colourings.

The best idea if you wish to provide your rats with top quality nutrition is to make your own mix. That way, you have more control over the ingredients, and the quality of them.
Some of the commercial rat foods are fine if given alongside something else, or if you only use them as a base and make sure the bulk of the mix is home-made, but I personally would not feed them exclusively for any significant amount of time, though other people do. I just personally like my rats to have a bit more variety in their meals, and I am a believer that variation in the diet is beneficial to health. I certainly wouldn't want to eat the same thing every day for my entire life!

There are not many truly great commercial rat foods available. And this is, sadly, true of commercial foods for all pet species, including dogs and cats: most are full of junk, filler, ingredients the animals don't need, and are generally produced as cheaply as possible to make as much profit as possible. You only have to look at the ingredients in a lot of dog or cat kibble to see this; most have a pitifully low meat content, sometimes as low as 4%, and the rest is colouring, wheat, cereal, vegetable matter and filler to bulk it out. And the meat source that is present is poor quality.

If you read the label on some of these commercial rat foods, one of the ingredients often listed is 'meat and animal derivatives', which is basically the parts of the animal that are surplus to requirements for human consumption, i.e, beaks, feet, heads, guts. 'Meat and animal derivatives' is a generic term for animal protein, and it can be sourced from any animal. Do you know whether its chicken, horse, donkey, dog, rabbit? These ingredients are cheap forms of protein, they are chosen for their low cost, not their quality. As such, there is no quality control on them, meaning you never know what is in the food from one bag to the next.

Most commercial foods contain colourings which are designed to make the food look more appealing (to the human eye, of course; rats are colour blind). Next time you buy a bag of commercial rat food, look inside and see if there are bright green, or red, nuggets in there. These are artifically coloured this way to make humans think they are prettier, and therefore, more appealing.

Two of the most common brands of rat food that I see used are Reggie rat, and Pets At Home own brand nuggets. These are usually what the rescue rats I get brought to me have been fed on, which is likely due to convinience as they are both easily sourced foods.

Sadly, neither are particularly good diets.
Reggie rat is often referred to as the 'McDonalds of the rat world', ie, its not a great thing for them to eat every day. You only have to look at how bright it is to realise how many colourings it must have in it.
Reggie rat also contains certain things that rats the world over just won't seem to eat. The mix contains alfalfa pellets, which rats find hard to digest, so most will not bother eating them.

Pets at Home rat nuggets are arguably worse, however.
They are small, round pellets, looking much like dog kibble. The meat source in them is poor quality, and many rat owners believe strongly that these nuggets increase the rat's chance of getting cancer due to the poor quality ingredients contained in them, the colourings and flavourings, and the artificial preservatives. Many people have reported an increase, sometimes a huge increase, in incidences of mammary tumours on their rats when they were fed Pets at Home rat nuggets, even if the nuggets were only part of a larger mix. Some rat owners avoid chicken specifically in commercial rat foods, as chicken for pet food is sometimes sourced from outside the UK from countries where chickens ingest chemicals known to cause cancer. This chicken is banned here for humans, but a lot of pet food chicken is produced elsewhere. With rats being so prone to cancer at the best of times, it makes sense not to increase that risk even more.
But that aside, the nugget/block style foods are incredibly boring for rats to eat, for life.
These block/nugget type foods were developed originally for use in laboratories (hence the name 'lab blocks' which is often applied to these kinds of foods) to prevent selective feeding. When a mix is varied, rats will tend to pick out the bits they like best, and leave the rest, which in a laboratory setting can mean the rats are all getting slightly different diets depending on what bits they eat most of.
So lab blocks were designed to combat this by putting everything into one block. That way, the rat can't pick bits out, he has to eat the whole lump. Can you imagine eating a single, square, grey block of food every day for the rest of your life? Imagine how an animal like a rat, a born scavenger and opportunist, feels eating exactly the same thing day in and day out until the day he dies.
If you have to use a food from Pets At Home, choose the museli style mix over the nuggets, as this is a slightly better quality food.
Some commercial mixes are better than others as stated above, but I have yet to find a rat mix that I would feed to my rats on its own, without anything extra added to it.
Does this mean you need to panic if you've always fed your rats Reggie, or rat nuggets? No. They're not about to drop dead.
But there are far better options for feeding your rats which will be healthier, and more interesting for them.

Many rat owners are now avoiding mixes marketed for rats altogether, and instead feed mixes marketed at rabbits. This is what I do.
Rabbit mixes are preferable to many of the rat diets, as they are vegan. This means the food isn't full of low quality animal protein and slaughterhouse floor sweepings. You can then add back animal protein using your own choice of quality kibble/meat/fish. Burns is a decent dog kibble; I try to use the fish varieties where possible.
The rabbit mix I use as a base is called Harrisons Banana rabbit brunch, which I buy in 15kg bags for around 13, though it comes in smaller bags too for those with less rats! Other mixes rat owners often use include: Alpha herbal, Mr. Johnsons Supreme rabbit mix, and Allen and Page.
To my base of Harrisons Banana Brunch, I add:
Cereals - Use only plain cereals. Do not use sugary cereals like frosties or sugar puffs, or anything with added sugar or salt. I change the cereals I use each time I make a mix, and it often depends on what brands are on offer, but I often use bran flakes, shreddies and/or weetabix/shredded wheat.
Oats - I buy a box of Jordan's thick porridge oats, usually, but any brand of chunky, rolled oats is fine.
Brown rice - This is a good source of zinc, and vitamin E. I usually cook this for my rats, as I think its more interesting for them, but Im assuming it can be fed dry with no issues too. Dried pasta - The whole wheat kind is the best, but normal or tricolour pasta won't hurt them. I find my lot like the spiral shapes the best, but I have no idea why! They tend to get more pasta in their mix in the winter, as it can make them gain weight. So if your rats are looking a bit podgy, cut back on the pasta for a while.
Rice cakes - Plain, wholegrain rice cakes can be broken into pieces and added the mix.
An animal protein source - I like to use a good quality dog kibble, like Burns or Skinners, or even dried mealworms. But you can use anything for this, from tuna to chicken bones, to a hard boiled egg.
Seeds - I tend to vary which seeds I use, it depends very much on what is on offer and what I have access to while shopping. Pumpkin seeds are good, as are hemp seeds. Sunflower seeds are ok if used sparingly, but too many will make rats fat, leading to a higher risk of mammary tumours.
Extras - I sometimes add nuts, herbs, or dried fruit to my rat's mix. This is usually if I come across a good bargain on them. Nuts are high in fat, so tend to be more of a treat, and dried fruit is given sparingly also. I will also occasionally add supplements, like garlic powder or seaweed.

Once or twice a week, my rats get a bag of curly kale. This is extremely good for them, particularly babies, and an be purchased from Tesco, Morrisons and various other places.

This is simply what I feed as a base/everyday mix, to give you an idea, but my way is not the only way, its just the way that works best for me.
But we're not done yet!
A good percentage of my rats daily diet is fresh food.
Rats get a lot of benefit from fresh foods rather than just having their dry mix every day. If you have rats, you need not throw away your table scraps anymore! Rats will get a lot of enjoyment from things like potatoes, eggs, bread, vegetables, fish and chicken. Rats also love meat bones as it gives them something to chew on. Do not worry about your rat choking on cooked bones, as dogs or cats can, because rats grind all their food up into a powder before they swallow, so there is no risk of this.
The foods my rats get as part of their fresh diet varies depending on what deals I can pick up at the supermarket. Last week, they had raw lambs heart, and tomorrow they are having fresh trout. If I see something marked down, I buy it for the rats, so they never know what Im going to come home with for them next!

In the wild, rats would not live on strictly dry, crunchy foods; they eat a huge variety of things like eggs, berries, nuts, carrion and human-left overs.

In my opinion, rats should be provided with an omnivore diet, and not have to live as vegetarians, and certainly not as vegans. Even if you only provide a small amount of animal protein via eggs, I believe this is vital. Growing babies and nursing mums definitely need animal protein and should not be made to live as vegan, as this can be damaging to their health.
This species has evolved as an omnivore one.
Nature does not make mistakes when it comes to shaping the diet of a species.
Your rats don't require an animal protein source every single day, (in fact older male rats should have limited protein as most old boys have a degree of kidney failure and excessive protein can affect this) but they do require an animal protein source to be in top condition, particularly young babies and nursing mums.

There are only a few foods that are an absolute NO for rats, but obviously there are many foods which are better for them than others, or are to only be fed sparingly.
Male rats cannot have oranges as the pith and skin contains an oil that contributes to kidney cancer. This only applies to males, however, and it is said that if you remove all pith and wash it off and just give them the flesh, it will be fine. Personally, I do not take the risk.
You may occasionally hear people claim that chocolate is toxic to rats in the same way it is to dogs. Well, yes and no.
The amount of chocolate a rat would need to eat in order to become ill or at risk of death is so ridiculously huge that it is of no relevance. A small amount of a chocolate now and then will do no harm to a rat, and in fact, rats with breathing trouble can benefit from a piece of dark chocolate as it helps open the airways. Rats love chocolate, and chocolate pudding or spread can be a handy tool for hiding medications in, also.

Like us, rats tend to prefer the things which aren't as good for them. Rats adore biscuits, chips, pizza, anything greasy or fatty, but these should only be fed in moderation, if you give them at all. A treat now and then is fine but just as you yourself wouldn't eat such foods every day, your rat shouldn't either.

Baby rats have slightly different dietary requirements to older rats. They need more protein due to their rapid growth. You can provide this with a small bite dog kibble with a protein content of about 20%, cat food (high-life foil tray cat food is good) eggs, or chicken bones with some meat still on.

There is a very good book available called 'The Scuttling Gourmet' by Alison Campbell which goes into rat nutrition in great detail. It is a must have for all rat owners.

Rats love eating so be creative!

Click me!