The breeding of mice is the easy part, just put a male and female in the same cage and you should have babies soon after. That was easy wasn't it? What you should know about breeding mice, you should learn before you have babies to care for.
| Why Breed Mice? | Some Facts | Selective Breeding | Inbreeding | Strain Breeding |
| Ideal Markings of Mice |
Think thoroughly what are your reasons for breeding mice. Are you planning to take part in shows with your mice? Are you interested in breeding only pet mice (note: "only" in this conjunction means that you are not interested in breeding mice with standard quality appearance as well as perfect pet qualities!!!) to satisfy a need for pet mice in your are? Do you want to breed only one litter from your mouse female?
In all these cases you need to know those things mentioned above! If you're interested in breeding mice and showing them, you also need to learn about genetics and colour inheritance. In any case you need to understand the meaning of "inheritance" and how it works. Not only colors and markings are inherited - it applies also to health and temperament!
You have to know about proper breeding "techniques" and understand the meaning of words "inbreeding", "line breeding" or "outcross".
If you are interested in breeding mice so that others in you area are able to get them from you,
Breeding mice for fun may be fun for you, but for your mice it is always a stress. Females do not need to have at least one litter in their lifetime in order to be happy - in fact not breeding from your females can give them a longer life with a smaller risk of developing a mammary tumor. Furthermore, the babies you produce may not be at all happy to exist - especially if you have dumped them in a bad pet shop or have sold them to the first one that's interested without checking the new owners' knowledge and facilities! They did not ask to be born - it was your idea!
At some point each breeder notices that in her animals there are some faults and that because of that they do not do as well in shows than animals of another breeder. Therefore the breeder tries to combine her animals in a way that the offspring would be better than their parents. And like without noticing it, the breeder has changed from random into selective breeding.
Selective breeding can be described as being systematic breeding of animals in order to change certain qualities in them. With selective breeding of pets, the question is about systematically improving the animals to resemble the written standards laid down for them. With mice this includes improving their colour/markings, type and - as they are pets - also their temperament and health.
How is the breeder able to improve the quality of her animals? Three key words are Goal, Feedback and Sustained effort. This seems to be clear, does not it. In reality this is not always the case. The goal is lost easily as the years (or even few moths) pass by as the first litters were not what they should have been. Feedback is taken overtly critically or even arrogantly (the judge does not know a thing, there is nothing wrong with my animals). And last but certainly not least, sustained effort is the first one to be forgotten - the breeder becomes interested in other hobbies than the breeding of mice.The goal is one of the most important things to consider before even starting to breed mice. Make a decision what kind of mice you really want and stick to that decision.
If the breeder acts like a weathervane -- breeding Champagne Tan today, Black Eyed Cream tomorrow and after that long hair mice - it is easy to understand that she cannot improve a thing, she can only scratch the surface.
It is not sufficient for the breeder to decide that her mice will win prizes. In fact it would be far easier for the breeder to buy good mice from other breeders and compete with them.
You should consider following details:
Choose only one colour or marking and stick to that decision. It does not matter if that variety does not do well in shows at first. You will have more reason the be proud of your breeding once it starts to show some results.
Decide the colors and markings you want to breed and develop. Do not get greedy. Choosing too many colors you will not be able to concentrate well enough in any of the colors without getting some hundred breeding mice. Monitor closely the level of quality in the colour you have chosen home and possibly abroad (mainly Britain). If the general quality is quite bad in your area, you may have to consider importing mice. Find out what are the good and bad qualities usually present in this colour. Compare your animals with the general level of quality, are they clearly better or worse. Here you should be as critical and honest as possible. If your animals are better or at least of the same quality, you have far better chances of succeeding in your selective breeding. If your animals are clearly worse, you should consider changing your breeding stock. Starting selective breeding in poor quality animals really takes time and patience.
How much space you have for your mice gives some limitations to your breeding. If you do not have a spare room for your mice, you cannot have so many of them. Mice do stink even though you changed their beddings every single day and the more mice you have, the more time it takes to take care of them.
Cooperation with other breeders is very important. Selfishly aiming at your own benefit and getting "fame" is shortsighted, which eventually will harm yourself. In some point you will need new blood in your strains and if the general level of quality in mice is quite bad, it is really difficult to get a good breeding mouse.
The only way to monitor the development of your breeding is feedback and analyzing it. Write down information on each litter, so that you can remember even after years of time what kind of mice each combination produced. Write down faults, but also successes. Also follow the development of the mice you have bred after they leave home; what they grew up to be, how do they make in the shows and what kind of offspring they get.
Compare the offspring with the parents. Are they better than their parents? What qualities have they inherited? Can you tell what qualities were inherited from the mother, and what from the father?
One very important factor is the uniformity of a litter. This does not seem to be clear to all breeders, which I find amazing. After all, uniformity tells a lot about the genetic make up of the mice. A litter with one excellent mouse with the others being mediocre or worse, is not a good litter when it comes to selective breeding. The sole excellent mouse can carry the poor qualities of its siblings and pass them on to its offspring. A uniform litter is a sign that they will also have offspring of uniform quality.
One of the most important places to get feedback from are shows and different kind of breeders' meetings. In shows you can present your animals to the judge and to other breeders as well. Follow the judging closely and listen what the judge has to say about the animals you have bred. If possible, present a breeder's class even though in your opinion your animals are not good enough to win the class. You will still get the judge's opinion on the overall appearance of your animals and whether you have progressed or declined in your breeding. Some judges give valuable advice on how to breed out certain faults in your stock.
It pays to show your animals even though you are still only starting your breeding. Particularly with rarer varieties the judge will be very interested in the animals shown. At the same time you are helping the judge to form an over all opinion on the quality of the variety in question.
There is always a danger of becoming "blind" to the faults in your own animals. Usually the breeder becomes upset if the judge remarks on the faults present. It is easy to understand that at this stage the selective breeding work usually comes to a halt. It cannot develop further, if the breeder sticks to her beliefs on the quality of her stock. Have a critic's eye when you monitor your animals and think if it is worth using and are you heading in the right direction. Remember your goal.
Sustained effort
The results of selective breeding are often visible only after years of work, but it is hardly possible to ever breed the perfect mouse. With good luck you can get a Best of Breed mouse from the first litter, but more probably it will take you several generations to breed a winner. So, be patient and aim consistently towards the goal.
Sustained effort is needed especially when they are setbacks in the breeding work. These can be hereditary illnesses, unusual aggressive behavior or other faults. In the worst case the whole stock may die of food poisoning or a deadly disease - this has happened. This kind of situation is very depressing for the breeder, years of work have come undone and she feels like there is nothing to be done.
If there are other breeders working on the same variety, the situation is not really that bad. You are able to start anew by obtaining good animals of your own strains from other breeders. As the you have long time experience on your variety, you will soon reach the level of quality you had, sometimes even better.
If you were the only one breeding the same variety, it takes a considerably longer time and effort to create everything anew. Still, you are able to avoid many mistakes you did the first time around and the result may be a stock of far better quality than before.
Even though your breeding is guided by the standards of excellence, you should always remember that you are breeding pets. The temperament and health of your animals are of utmost importance. They should be tractable and friendly, with mice the does should be able to get along easily. Different hereditary illnesses are a warning signal, implying that your breeding is going into wrong direction. If hereditary illnesses do occur, never sell these animals to pet shops. They may end up getting bred from and therefore contaminating other strains of mice as well.
Close Inbreeding
The closest possible inbreeding is to mate a parent and its offspring together (mother and son, or father and daughter). This way the mated animals share half of their genetic make-up as offspring inherit half of their genes from each parent. Almost as close a form of inbreeding is to breed siblings together, as they will have a similar, but not identical, genetic make-up.
Close inbreeding is used to fix desired qualities in the strain; for example, new colors or coat varieties, desired type or size. Although close inbreeding is an easy way to get uniform siblings with the desired qualities, it is also a way to fix unwanted qualities - for example lowered fertility and hereditary diseases. That is why close inbreeding is not a highly recommended breeding method in the long run.
Using close inbreeding is like putting all of your eggs in one basket. As long as the animals are healthy and pass on the desired qualities, all is well. However, if and when they start to pass on unwanted qualities, the whole strain can be ruined. If you decide to use close inbreeding, you must always carefully select the animals used for breeding and look for possible hereditary diseases or bad temperament. You should never use unfit animals for breeding.
Moderate Inbreeding (the "harem" system)
Much more moderate than close inbreeding is using one buck and several does, so that the offspring have a common father but different mothers. The doe and buck mated are thus always from a different dam.
Strain breeding (a.k.a. Line breeding)
One form of moderate inbreeding is strain breeding, where the breeder focuses attention on certain exceptional animals, usually bucks. This means that the founding buck of a strain will appear as many times as possible in that strain. Thus the same buck is the forefather of both parents several times in the pedigree of the offspring. Followed strictly, this can be a very misleading method which will not give the desired results. It is easy to forget that the offspring inherit half their genes from the dam. If the breeder does not monitor the quality of the females at all, the result is of mixed quality; the offspring may be good but they may be very poor as well.
Strain breeding combined with strict monitoring of the does, usually produces the best results. This means that only the best does are mated with the best bucks, so that the offspring have the greatest possibility of inheriting all of the good features of the strain.
Colour Strain breeding
One form of strain breeding is colour strain breeding, where in addition to the normal strain breeding the animals mated are of the same colour or genetically compatible. With rodents in particular, where great attention is paid to the coloration and markings of animals, colour strain breeding combined with appropriate out crosses is the most recommended breeding method.
Wide Inbreeding
When several bucks and does are used while forming a strain, it is called wide inbreeding. These are mated together, avoiding brother-sister matings and limiting the use of half-brother to half-sister matings.
Out crosses
An outcross is the mating of two animals from completely different strains. Breeding based entirely on out crosses doesn't often lead to good results; the quality of offspring can be vary varied even with the best animals. The main problem with using out crossing as a primary form of breeding is that an unreasonably large number of breeding animals are needed and often after a few generations the breeder is in a situation where many of her animals are related to each other to some extent (thus she is no longer out crossing).
Most breeders find strain breeding, improved with thoughtful out crosses, to be the most rewarding method. This means that the animal used to improve the breeder's own line (the outcross) must be of extremely high quality or must have some desired trait such as a new colour or coat variety. One must always be careful with out crosses, as along with desired qualities the strain may get unwanted problems such as inherited diseases or bad temperament.
A Breeder should never outcross randomly simply to see "what might happen" with a particular combination or "just to bring in new blood". Generally, if the outcross did not give the desired results, you should not use the offspring in your own strain.
About Forming a Strain
It is impossible to form a strain without at least moderate inbreeding, as this is the only way to come up with animals of even quality. A strain can be described as being:
" ... a group of animals, carrying similar qualities and producing similar offspring."
There are good and bad strains; some strains develop for the better some for the worse. The aim of a breeder is to maintain the highest level achieved or, better yet, to further develop and improve it. Many strains can be developed further into different branches, where the qualities of the original strain are maintained with a number of new qualities added.
It is easier for a rodent breeder to form her own strain, than for breeders of other livestock; rodents breed faster and take up less space than, say, horses or dogs. Where a bigger animal has had one generation, a rodent may have given birth to dozens. There is a risk in this, as using poor breeding methods can cause a major catastrophe over generations and ruin an entire strain. If this happens, the breeder seldom has the desire to breed any more.
Classic method
In Britain a rodent breeder usually starts with four animals; one buck and three does. This is why it can be very hard to make a British breeder to understand that you want to buy only one buck or doe. All three does are mated with the same buck. Of these litters, keep one buck of one litter and mate the does of the other litters with him. Of these litters, again keep one buck of one litter and does from other litters, mating the does with the buck, etc.
With this method you can quickly get good results, especially if the founding animals have been of high quality. If there have been latent or visible faults in the founding parents, they usually will emerge very strongly in the young after a couple of generations. At this point the breeder gets distressed and usually tries to use unconsidered outcross ruining the forming strain thoroughly. Instead, the breeder should start very harsh culling, that is no to use mice with unwanted qualities for further breeding.
If you use classic breeding method you should pay great attention to the founding stock. If these animals are mediocre, their offspring will be mediocre. All animals should have the desired qualities, i.e., good colour, type and size. There should also be as few as possible faults, i.e., the animals should be as healthy and good tempered as possible. It would be wisest to obtain the founding stock from different breeders in order to have a wider original gene pool. Thus you will be able to get greater variable in the offspring; so by choosing the best mice for future breeding also the best genes will be chosen.
Using Several Founding Bucks
In the method of several founding bucks the breeder uses two, sometimes even more bucks instead of just one. There can be three does, but preferably more. You should choose the bucks using the following method: both bucks should have as many as possible of the desired qualities and neither should lack the same quality. The same goes for the females too. You should have the desired quality present always in one of the founding animals.
While using this method, you should also pay close attention to hereditary faults and illnesses, especially as they emerge more slowly than in the classic method.
Rare Colors, Markings and Coat Varieties
Rare colour can be described as having only a few existing mice. Usually these colors are imported from abroad as new colour- or marked varieties or they are unpopular for some reason (= they haven't done well in shows for a while). The genetic make-up of these colors and markings are usually well known, as well as if it's lethal or not. However, it takes a lot of effort and time to breed these rare varieties. The show success isn't often very good.
You should obtain 2-4 mice at first, preferably does than bucks and check them critically. Most prominent faults are usually small size and poor type but there can also be troubles with the main colour. The strain needs new blood as it can be already very inbred. It pays to use a top-quality buck or to obtain a few bucks that go with the variety you are working on with. These bucks should be very good in quality and they should not have the same faults as the rarer specimens.
The rare-coloured females are mated with these bucks. If the desired colour is dominant, all of the litter will usually be of this colour. If the desired colour is recessive, are the young carriers of this colour. The young are then mated together, but not siblings and preferably not even half-siblings. At this point there should be mice of the desired colour. Of these mice the best are mated together and so forth, so the desired type and size will be slowly stabilized in the strain.
New Colors and Markings Born as Mutations
Sometimes a strange coloured baby crops up in a litter. Before you start breeding more of these "excitingly" coloured mice, you should make yourself clear if this colour or marking is worth the trouble. New colour or marking should differ considerably from the varieties already existing. You should look for a similar colour or marking (or coat variety) in another species; if there is one standardized, you can start stabilizing a colour in your strain.
As there is usually only one specimen of the new variety, you should mate it with one of the parents or its sibling who can be the carriers of the same feature. If the new feature is dominant, the whole litter has the desired quality. If it is recessive, will the whole litter carry this quality even though it will not show. When these mice are mated with the parent having the desired feature, should some of the young be as desired. These mice are then mated together to get enough founding stock. In the first stage you have to mate together only close relatives to get more mice with the desired feature. You usually have to give in with type and size too.
Only after you have stabilized the desired feature and you know a little more about it (i.e., is it dominant or recessive, is the gene lethal and is the colour caused by several genes), you can start breeding in size and type using similar methods as with other rare varieties.
Remember
Even though you attempt to mate only good animals together, so that the young should also be good, there may be misfortunes. The young may have hereditary faults or illnesses. You may not use these mice for future breeding. Be careful with where these mice end up. You should not sell them to pet shops, as someone may buy them and use them for breeding when these mice can pass down their faults. It's better to try and find new homes for these mice yourself, as long as you remember to tell the new owner that they should not be used for breeding. In the worst case, if the mice have faults that make their living difficult, it is far better to euthanize them.