Rat Health Care & Information

Breeding Rats

Your Rats
Breeding & Showing
General Info

Why do you want to Breed?

Selection of Breeding Rats

The Birds and the Bees!

Pregnancy and Birthing

Care of the kittens

The sections below are written with UK breeders and breeding in mind. As a general rule, we do not have the 'feeder' rat issue as it is illegal to sell live foods in UK pet shops and also we do not have quite the same issues with quarantine and SDA type infections as the USA has.

Please check out the article on Mentoring for new breeders

Why do you want to Breed?

You should ask yourself quite a few questions before considering breeding from your rats. The most important one must be, what are you going to do with anything up to 20 kittens! There is far more to breeding than putting a buck and doe together!

Why do you want to breed? Breeding is not cheap - new cages, extra food and bedding and also potential vets bills will all need to be considered. If you are breeding for show, then you need to consider genetics and obtaining quality stock from the relevant breeders. Choosing the right homes for your kittens can be hard. Things can go wrong, worst case scenario, does can actually die giving birth, although it's not that common. Lots of time to socialise the kittens is needed as well. You should have aims and objectives of what you are trying to achieve in breeding each litter you breed. It is highly recommended to find yourself an experienced breed to mentor you in your new venture.

Homing of surplus kittens? by being listed on a rat club breeders list (NFRS do one - breeders@nfrs.org), personal websites, online forums, and word of mouth/friends. Would you be prepared to keep anything you cannot find homes for? - if the answer to that one is no, you shouldn't be breeding! It is worth sounding out your possible outlets before you decide whether to breed or not. Some breeders do cull unwanted kittens and even older rats, but that is down to personal ethics. Many reasons are given for culling - does not being able to raise large litters, poor type in rats, not being able to home the kittens, disposing of unwanted colours and markings within litters, and more. I believe that quality pet rats and show rats can be produced without the need for culling and my rats have proved this many times by reaching champion status and winning pet classes. Some of the breeders who cull kittens also cull retired adults, so are unlikely to know the longevity of their lines or the health beyond about a year old.

Genetics and temperament. Both important. You can have the most wonderful temperament rats in the world, but if they have any genetic defects or there are genetic defects in the line, they should not be bred from. I feel that it isn't actually about temperament as such, but more about the personality of the rats - rats should have character while being people orientated and friendly. Bear in mind that if your favoured variety is of colours that are difficult to home (will explain the very basics of colour genetics later!), then it's probably better not to breed from them when you first start breeding, unless you know you can find homes for a full litter of the less popular varieties or plan to cull! As a breeder develops a reputation and gets more well known, they do generally find it easier to find homes for even the less popular varieties. If you have a preference of which varieties you wish to breed, then you need to select rats accordingly. I think it is really important for a breeder to breed the variety (or varieties) they are passionate about.

Cage space. You need at least 2 reasonable sized cages for the kittens if you plan to breed. Assuming you get 2 young does for breeding, you cannot guarantee that these does will live together during the period of one doe having kittens. If you breed both at the same time, (which I wouldn't necessarily recommend as you could be looking at 30+ kittens in one go!!) you should not leave them together as they can steal kittens from each other and can fight over them and end up killing them or one doe can end up nursing them all leaving the other with none. Assuming that you breed one doe and she lives quite happily with her mate through the birthing and kittens stage, you would still need cages to separate bucks from does at between 4-5 weeks of age. Kittens grow very fast and by 5 weeks need a lot of space to run around in as they have so much energy!

Basics of colour and coat genetics. Certain colours and coat types are dominant - means that if one parent is that colour you will get a percentage of that colour or coat type in the offspring. Rex coat is dominant and rex to straight coat will produce approximately 50% rex kittens. Rex mated to rex produces double rexes which are virtually hairless - generally it is not seen as good by the fancy to do this mating.
Other colours are recessive, which means that both parents either need to 'be' that colour or 'carry' that colour in order to produce kittens of that colour. If you have a pedigree of your rat, you may be able to predict the colours that are likely to be carried from what else is in the pedigree, but you can only prove whether they carry it by mating to a rat of that colour. Basically speaking, if you mate rats that don't carry the same colour genes, you will get either black or agouti kittens! In rats you have Agouti based colours and self based colours. Agouti colours include: agouti, cinnamon, blue agouti, topaz, silver fawn. Self colours include: black, blue, mink, chocolate, buff, champagne. Some recessive colours such as the Siamese/Himalayan can be based off either self or agoutied varieties. PEW is an albinoism which can be any colour which is masked white by the albino gene, so is the most unknown variety going as you can't even tell if it is marked or what variety it actually is. If you mate an agouti based colour to a self, you will get agouti based colours and most likely a percentage of agoutis, unless the agouti carried self, whereby you would get a percentage of selfs as well. If you mate self to self, you may end up with that self colour or blacks as blacks are the most dominant of the self gene. Then we get onto marked colours such as hooded, Berkshire, capped, etc. If you mate a unmarked rat to these, you will most likely get Berkshires and Irish. If you mate a Berkshire to a capped you might get Berkshires, hoodeds and variegated. If you mate a capped to a capped, you might even get black eyed white as well as some capped. The easiest way of explaining this is if you mate something to something else that is the same colour or markings, you should get a reasonable percentage of this marking or colour in the litter, but if you mated an unknown pedigreed black to an unknown pedigreed PEW, you will most likely get agoutis and black if the PEW is agouti based, with a possibility of any markings as you don't know what the PEW is at all!
The above is nothing more than the basics on genetics and I have written an article on genetics, plus there are some far better written articles on genetics online: -

Maplewood Rattery Genetics Tutorial

Siamese Rat Genetics

Other good articles on breeding rats: -

Breeding: Can you live with it? RMCA article by Mary Ann Isaksen

The Rat Fan Club - Breeding Rats From Debbie Ducommun's Rat Health Care book

Selection of Breeding Rats

To find rat breeders in the UK, contact the NFRS for a breeder listings or check out the NFRS members forum. Many breeders have websites, so you can get a bit of idea about their breeding lines and ethics from them. If you have a regional club based locally to you, it is worth contacting the officers to see if they can point you at local breeders. Don't expect to find the best breeding stock on kitten tables at shows (of which most rat clubs don't actually permit these now) or in pet shops! Also remember that no breeding line is perfect - all breeders are constantly working to improve their rats generation by generation, so don't expect to find the 'perfect' rat anywhere! Breeders will never let you have their best rats to start your own breeding line as they would be keeping these for themselves, but should be prepared to give you fair rats that will be an ideal starting point for a new breeder.

Choosing your stud buck

Alpha Centauri Paris - agouti stud buck

It is important to choose the right stud buck as he will be key in the formation of your lines and can be capable of siring kittens often until over 2 years of age. Bucks are normally happy living in small groups or pairs and it is not ideal for a buck to be purchased to live alone.

Temperament - Ideally a buck should not be used for stud until he is at least 6-9 months old as bucks can go through a 'testosterone' phase where they can become aggressive and dominant in their behaviour. This phase can either not occur at all or may occur any time between 4-8 months of age and can continue for any length of time, which can in some cases become so unbearable that castration is the only option. Obviously this sort of temperament is not something you want passed onto your kittens, so be prepared to wait until the buck has matured, although experienced breeders do often use bucks from well known lines a bit earlier. By this age the buck will also be fully grown, so you will be able to see he has been healthy until then and made good size and type as well. It is worth also considering that using bucks that are 'old' can cause genetic defects in the kittens, so while it is a nice option to wait and see how healthy a buck is into his old age, you could be contributing problems to the line by doing this. Most breeders don't tend to use bucks over 2 years old unless the buck looks really young for his age. Also many bucks are infertile by this time anyway.

Health - The health of your buck should be good - again a reason not to breed from a rat too young. You should not breed using a buck that has had chronic respiratory problems or any other sicknesses that have required lengthy antibiotic treatment.

Meet the family - When you are looking for a kitten buck for potential later stud, try to meet the parents of your rat and also try to find out as much about the rest of the rats in the line as is possible. It is useful to have some idea of longevity and whether there are any known health problems in the line or tumours. Unfortunately this information is sometimes not available as some breeders do not keep good records and also some breeders cull, both reducing litters and also culling rats that are beyond breeding age.

Size and type - A good stud buck should be solid and muscular, almost 'brick' shaped. I don't like to breed from bucks that are under 500g in weight, but prefer them to be around 600-750g. He should be solid with good bone structure, but not fat. He should have a broad head and his nose should be blunt and not pointed (doe like). He should have a nice thick set tail, which should be the length of his body. He should have good sized eyes which are of even size and nice shaped ears. It is highly recommended to visit a few rat shows and ask experienced breeders or judges to show you what a good stud buck looks like.

Choice - As most people buy kittens at 6 weeks old, there will be many buck kittens that will never make suitable breeding rats and their suitability needs to be assessed the whole time they are maturing. It is often worth buying two brothers if you have a liking for a particular line, as it is almost certain that one will make better stud buck than the other will and it will give you the choice. Just before you are ready to mate your stud buck for the first time, it is worth going back to his breeder and asking if there is any new data on the line and his siblings that you should know about before breeding. You may even be better asking to use a stud buck from another breeder and taking your doe for a visit for those initial litters so you can gain experience by being mentored by a more experienced breeder and using a proven stud buck.

Learning more - If you are a novice at selecting rats, always feel free to ask experienced breeders and off-duty judges. When going to shows, look at the bucks that have been placed high in their classes. There is a specific class for stud bucks which all adult bucks are eligible for, so try to have a look at the bucks that have been placed high in this class. If you wish to breed a specific variety, contact breeders who breed this variety and talk to them about how to go about breeding them yourself. You may find that some varieties are very popular or harder to breed and you may have to go on a waiting list to find the right rats.

Stud services - Many breeders will allow you to bring your doe to their rattery for stud. This can be useful for outcrossing or keeping your own numbers down, but ensure that you have agreed a 'fee' before the actual mating. Usually one or two kittens in exchange (ensure you agree who gets pick of the litter before the mating) or a small monetary fee or food/gift can be agreed. Although some breeders will agree to the buck visiting the doe, it is normal for the doe (and maybe a cage mate to keep her company for the nights she is not in season) to visit the home of the buck as bucks do not take so easily to moving house as does do.

Choosing your breeding doe

Valhalla Artemis - black eyed cream brood doe

Now you know how to select your stud buck, you need to look at selecting suitable does for him. Much of what has been said above about temperament, health and talking in length to breeders about the rest of the family is still very important.

Breeding age - Does will generally not be bred from under 4 months old, and ideally should be bred from before 8 months old, particularly if you are considering a second litter as well. There are some people who believe that pelvic fusion can occur after about 8 months, but while I know this can happen in guinea pigs, I have never heard or seen any evidence in rats to support this and this is probably nothing more than a myth spread by internet websites. Personally I would not allow a doe to have her first litter over about 10 months old with my ideal preference being 5-6 months old.

Health - Does are more prone to mammary lumps than bucks so apart from ensuring that the doe is healthy up to the time when you are ready to breed from her, it is worth trying to find out if there is any history of mammary lumps in the lines.

Temperament - Only choose the best tempered does, and this should help to pass on good temperament to the kittens. Does are generally more lively than bucks, but they should be 'friendly lively' not 'skittish lively'.

Size and type - Does should have a long, racy body without too much fat. The head should be longer and more pointed than the bucks and the eyes should be good sized. Generally does look more leaner and fitter than the bucks and fat does rarely get pregnant easy, so it is important to keep them lean and fit and not overfeed them as kittens or teenagers. I like my does to weigh at least 300g at the time of mating and most tend to be nearer 350g but if they get much over the 400g mark, this is where problems often occur. Does tend to grow with their first litter and are usually slightly bigger afterwards.

Learning more - As above with the bucks, visit shows and ask experienced breeders and off-duty judges to show you nice racy brood does. Many breeders keep more does than they plan to breed from as a just in case, so by asking around, you may be able to obtain a doe that is nearly ready to breed.

Outcrossing, Line breeding and Inbreeding

A lot of people ask why it's ok to inbreed animals while when humans inbreed it can cause health problems. For experienced breeders, inbreeding and linebreeding are used as 'tools' to improve the lineage and help keep problems out of the line.

There are several excellent articles online explaining these breeding methods.

The Birds and the Bees!

Once you have selected your breeding rats and they are both in the peak of fitness, it's time to consider the actual mating. One thing I would highly recommend in the weeks before doing the actual mating is to get into contact with the breeders of your rats and ask for an update of parents, siblings and other relatives in the line. If you discover you actually have the only rat from a litter which have all been sick or had problems or parents have died from illness or there are tumours appearing in the line, you may want to reconsider whether to use your rat at all in your breeding lines!

Study your doe and you will notice that every 5-6 days she is 'in season' - the symptoms of this being arching back when you touch her back near her tail and sometimes waggling the ears as well which is known as lordosis. Sometimes other does will try to jump on her during this time. (Bear in mind that it is not unusual for does to not come into season at all during some of the winter months and even when they do, quite often they will not get pregnant - it seems to be natures way of saying it's not the best time of year to breed.)

You have 2 choices for the actual mating time, either you can leave a buck running with the doe for a few days or even a week or more, or alternatively you can watch your doe and when she shows the symptoms of being in season, put her and the buck in together for a few hours or preferably overnight. I prefer the second as my bucks go back in with their cagemates easier if they are only out for a one night stand, than being away for days or weeks and also I know exactly when they were mated which gives a better idea of when they are due, whereas if they are running together, you will probably have no idea when they were actually mated. While they are mating, keep an eye open for distress, some bucks can be a bit rough and make the doe bleed slightly, and she should be removed immediately if this should happen. Sometimes you will notice afterwards that the doe has a whitish plug in her urethra opening - this is a good sign.

If you decide to leave the buck in with the doe for the full term of her pregnancy, ensure you remove him just before she gives birth as does usually come into season immediately on giving birth, which means he could mate her again!

Pregnancy and Birthing

Gestation period for rats is normally 21-24 days, although it can be as long as 25 and there have been cases of delayed implantation recorded that have allowed the pregnancy to go on for as long as 35 days on rare occasions - there are often problems if the pregnancy extend for more than 24 days though.

During the pregnancy you should maintain a good healthy diet for your doe. Do not increase the diet during pregnancy as this can cause birthing problems if the doe becomes too fat during pregnancy.

You can choose to weigh your doe while she is pregnant but this is not really recommended and can cause her to reabsorb. Does gain between 30-60g per week during pregnancy and generally gain between 100-150g total. Most breeders prefer to not handle their pregnant does much during their pregnancy period though as this seems to sometimes cause the does to reabsorb their litters. Personally I try to handle my pregnant does as little as possible while they are pregnant and once moved to the birthing cage, the only disturbance they get until after birthing is giving them food and water.

You will probably notice a temperament change in your pregnant doe, particularly as the time gets close to her birthing when her hormones are raging! Normally pregnant does temporarily rise to alpha in their cage, but some may become quite aggressive to their usual mates and need separating off earlier. Normally I put the pregnant doe in a nursery cage when they have about a 3-4 days to go. I will occasionally leave a sister or mother or close friend in with her until the last day - sometimes they are happy with this, but mostly they seem to prefer to be alone as pregnancy can be rather tiring and they do sleep a lot during these last few days.

Ideal nursery cages are the Rody or Duna type tanks with a Rody igloo for a nice secure nest. The Rody igloos split in half making it easy for inspection of the newborns without upsetting mum too much. Some breeders prefer not to use an igloo for a nest, preferring to leave the doe to build a nest in the nesting material. There is no right or wrong, just personal preference.

In the final few days, some does go into manic nest building and can build some amazing mountains, quite often including food bowls, toys, food, treats and anything else you leave in the cage for her! Not all does nest build until after the birth however so it is best to leave the doe to her own devices during these last few days and not to handle them or interfere with their environment too much.

Silvey with her rather impressive nest! There is a Rody igloo under that lot as well!

When your doe is starting the birthing, she will seem restless and will probably destroy her nest again. You may see a spot of watery blood at the urethra and the birthing should start soon after this. Usually it's fairly quick and the whole process is over in a matter of a couple of hours. If the birthing goes on for much longer, keep an eye on the doe for signs of distress, excess bleeding, signs that she is no longer having contractions even though it looks like she has more kittens on the way (uterine inertia). It is only a small percentage of birthings that will experience difficulties, but when they do, they can be fatal for either doe or kittens or both so making good judgements at this stage is important as they can be life and death, but also on another side of things, by disturbing the doe too soon after or during birth, you can stress her and cause problems. Uterine inertia is probably one of the more common, whereby the contractions have either stopped or are too weak to push the kittens out. This can be treated by your vet with Oxytocin, but this seems to have limited success and a caesarean is occasionally needed or the doe can be left to birth naturally if she is not showing distress. If the doe is not bleeding much and is showing no distress, she may well be capable of aborting the litter herself, but if she has become very large during pregnancy or is bleeding quite heavily, immediate vet care is needed. Bleeding or distress could be because of a blocked (fat, turned the wrong way or dead) kitten, so keep a close eye and if this is looking to be the case, see if the doe will let you massage her stomach, but again, there is a chance that a caesarean may be needed. Unfortunately when it gets to a stage of needing a caesarean, quite often the doe is too tired and weak and may not survive the operation or may only survive for a few days afterwards as the shock can kill them later. There are success stories though, so it's not a lost cause.

Another side use for Oxytocin is that it can start a doe lactating if she hasn't started, so can be used after the birth has completed as well. One of the keys to judging whether what is going wrong is likely to need veterinary assistance, is to check the colour of the blood and the consistency - watery 'red' blood is normal as long as it's not excessive, 'red' blood appearing to be more blood than water needs to be watched carefully. If the blood is darker red or brownish, the kittens are almost certainly dead inside her - she needs to be put on antibiotics at this stage to stop any decomposing kittens from causing her infection and keep an eye on her, but chances are she will pass the dead kittens by about day 27. Keep her on antibiotics for a week or so after a litter failure.


Sapphire during birthing - she gave birth to a litter of 15 healthy kittens!

If things do go wrong, you may need to find a foster mum very quickly and also make a start on hand-rearing them. Good articles on hand-rearing kittens are linked below: -

Caring for Orphaned Baby Rats or Mice

Raising Orphaned Rats

Fortunately, in the vast majority of rat birthings, things go very smoothly and you will have a healthy mum with a healthy bunch of little squeakers. I have found that the majority of does seem to give birth quietly while you are asleep or out!

Care of the kittens

Caring and correct feeding of the kittens starts as soon as they are born. Shortly after the mother has started giving birth, you can offer her tepid water with either sugar or honey in as they appreciate this far more than cold water. You should leave a bowl with her usual dry food in but in addition you should start supplementing the mother with an 'easy' diet - soft, easy to eat, protein foods, like EMP or Orlux (egg food for hand-rearing birds which rats love - soak to porridge consistency), eggs, chicken, tinned or pouched cat and dog foods (look for the good quality higher protein ones aimed at puppies and kittens), fish and anything else she fancies. Pasta, porridge, yoghurts, etc. are also appreciated. She will also appreciate tepid milk, either the baby formula or the ones intended for puppies and kittens are best - this can be either in a bottle or mixed with a little bread in a bowl. My own personal choice for a 'baby mix' is Orlux eggfood (doesn't seem to matter between the budgie and canary version, although I tend to use the budgie one) mixed around half and half with Vitalin original and then adding lactol powder and a little garlic powder and mixing dry - I then soak the mix to porridge consistency and give to mother and babies. You should be careful not to overfeed the kittens with supplemental food as you can cause them to grow too fast and get too fat as young adults and end up causing them to have birthing or breeding problems, so it is important to keep a good supply of their normal dry mix as their main diet.

Kittens are born completely naked apart from their whiskers (hence being able to tell rex from straight coat kittens as soon as they are born with either curly or straight whiskers!). By 2-3 days old you can normally see the patterns if they are going to be marked rats and also you can tell what colour the eyes are going to be from the pigment colour under the skin. The kittens eyes will remain closed until around 14 days, but during that first 2 weeks, they will grow considerably and also have their baby coats. They are born at approximately 5-6g and should be around 30-35g by 2 weeks old. Some kittens will blindly start adventuring and also start eating, while others are more interested in staying in the nest and letting mum do all the work!

Kittens should be handled from birth regularly on a daily basis. Scientific proof has been given that handling kittens from birth reduces stress and stress related illnesses in later life. I use the Ferplast Duna or Savic Rody cages as nurseries for the first two weeks as these are easy to 'steal' the whole igloo to look at the kittens away from the mother if she gets stressed seeing you handling them when they are very young. Most does become far less stressed about their kittens being handled when the kittens open their eyes and start moving around more and at this stage I prefer to move the kittens to a low level cage like a Ferplast Mary and give mum a hammock so she can escape the babies for a rest. 

Below are a selection of pictures from 1 day to 14 days: -

Esme's kittens - 1 day old                                  Amber's kittens 6 days old

Faith's kittens 9 days old                                                 Sophie's kittens 12 days old

Once the kittens have opened their eyes, they are usually up to mischief and into everything. Continue with some 'easy' diet with their main mix as the kittens will enjoy it and it will give mum a break as they will be getting quite a bit of the required sustenance from solid food.

Ana's 2weeks 3days               Alana's 2weeks 6days           Atalanta's 3weeks 1day

Bellona's 3weeks 6 days old                                                     Chelsea's 4weeks 6days old

As you can see from the pictures, they do grow up very fast!

Buck kittens should be removed from their sisters and mother between 4-5 weeks old. I tend to leave until about 4.5 weeks. The doe kittens can stay with their mother for longer if wished, she will stop feeding them anyway at just over 4 weeks old.

Kittens should ideally continue a higher protein diet until they are about 7-8 weeks old, then reduce the easy foods gradually to treat level. It is important not to overfeed as this can encourage the rats to grow too fast and also get fat and this has been linked to breeding problems later in life.

Article written by Estelle

Go back

 Send mail to Estelle with questions or comments about this web site.
Images & Text Copyright 2009 Estelle Sandford, Alpha Centauri
Please do not reproduce without permission
Last modified: February 08, 2017