Choosing rats to breed

Now that you have considered your motives, and decided upon your breeding aims, it is time to choose a pair of rats from whom to breed your first litter.

To some degree your aims will help you in making this choice. There are a number of points to consider in choosing your breeding pair:

• The temperament of the pair and as many of their siblings and close relatives as possible.
• The health of the pair and as many of their ancestors/relatives as possible.
• The longevity of the lines that you pair originate from.
• The general conformation and type of the breeding pair.
• The varieties that you are hoping to breed.

Let's look at these areas in a little more detail.

Temperament

Temperament seems to be significantly affected by inherited factors, behaviour learned from the mother and human influences after birth. The last bit you can influence regardless of which parents you choose for your litter, but you would be wise to consider the temperament of as many rats as possible from amongst the siblings and ancestors of your prospective parents (as well as the pair themselves, of course). Yes, your doe may be as sweet as honey but if a number of her brothers (uncles etc) have been experiencing problems with aggression towards other rats or their humans, you would be wise to reconsider. Ask breeders, ask owners, look for temperamental traits running through lines and ask whether you want your babies to display these traits (some traits are positive). If you plan to place the kittens that you breed into pet homes then you have a responsibility to make excellent temperament one of your aims.

Health

It is certainly true that many illnesses involve a degree of genetic pre-disposition and inherited factors. Whilst care, diet and environment all have a significant effect on health, it is good (as far as is possible) to breed from lines that are not prone to any specific illness and where the rats generally have a robust immune system. I say 'generally' because even within a strong, healthy line it is inevitable to have the odd rat who is more prone to health problems/infections. Breeding for health takes a good deal of patient perseverance - following up litters throughout their lives, acknowledging problems and addressing them. However, you will get off to a head start if you take the time to research the health of the lines your pair come from.

When considering health it would also be wise to discover what health issues (if any) are connected to the variety itself. Topaz and blue, for instance, have both at times been associated with bleeding disorders, megacolon occurs in chinchilla lines and some black eyed whites are deaf. This is by no means a comprehensive list. Find out as much as you can about the variety you are considering, before jumping in.

Longevity

It is extremely difficult to breed for longevity, since one cannot predict the lifespan of the breeding pair and longevity itself is influenced by many factors. It is worth considering though, the average lifespan of the rats in the ancestry of your chosen pair. One survey shows average lifespan for fancy rats in the UK to be 21.6 months. It is hoped that a good proportion of rats in any sound line will reach 2 years (and beyond). It has to be remembered that this sort of survey will be skewed by large numbers of rats from pet shops and rescues where health and longevity may not have been considerations in breeding programs. It would be unfair to blame breeders for everything, however, and care, diet, environmental factors and veterinary treatment available will all influence longevity (and indeed, general health). One method of working towards longevity is to select away from rats that have developed life limiting disease.

Conformation and type

Rats suitable to be bred from should be of a good size, well nourished and physically well developed/mature. Whilst the conformation that makes a rat 'show quality' may not be important to all breeders, it is certainly desirable to produce quality, well-proportioned kittens who are well endowed with the attributes that make a rat a rat. Breeding from small, weedy rats with small eyes and square tails will generally just produce more of the same. It is worthwhile to familiarize yourself with what a rat should physically look like (large muscular (fit) body - racy for a doe, brick-like for a buck, bold round eyes, thick cylindrical tail etc). Few rats are perfect, and your breeding pair won't be, but if you see a weakness in one (smaller eyes or a short tail, for instance) be sure that it is an attribute that the other in the pair is particularly strong in. Do not just select for 'bigness' as this does not equate to type or health.

Rats who are not physically robust may not cope well with the demands of pregnancy and lactation, and may also be more likely to run into health problems later in life.

Which variety to choose

Deciding upon which variety to breed is more than simply acknowledging that you have a soft spot for Silver Fawns. You will need to spend some time researching the variety that you are considering. Find out who else breeds them, what the strengths and weaknesses of the variety are, and (if showing is important to you), whether the male or female of the variety shows better. This may be important if you have a strong preference towards keeping bucks (or does). Consider which varieties will be produced alongside your chosen one, for example, agoutis from topaz lines. Find out which varieties are easier to breed. If you wish primarily to breed strong, healthy and longlived rats you would do well to chose a variety that has as few recessives as possible. New Varieties and some established varieties are really not for the fainthearted, or those who are looking for quick results. You will also need to consider whether your preferred variety has any health issues, related to breeding, specific lines or the variety in general. If temperament is important to you find out how easy it will be to get outcrosses for your lines who have suitable temperaments.

You do not necessarily have to begin with two rats of your chosen variety, indeed it may be preferable not to do so. Sometimes breeding two rats of the same variety (eg blue or topaz) can actually reduce the quality of the offspring. It is better to choose one rat who is the variety and one rat who carries the colour gene (where the variety in recessively inherited). With dominant genes, only one of the rats needs to have the gene concerned. The other advantage of this system is that the litter produced will not all be the same variety, which makes it much easier to place them into pet homes. Considering individual genes is outside of the scope of this article.

Relationship

A good place to start for a first mating is with related rats from the same line, perhaps cousins or uncle to niece. A later article in this series will consider inbreeding, line breeding and out-crossing in more detail. Frequent close inbreeding can potentially lead to problems, just as constant out-crossing can. Starting off with related rats (providing the line holds all of the desirable traits that are important to you) is more likely to help you achieve your aims than mating two unrelated rats (no matter how gorgeous they are as individuals). If they are more loosely related you have more scope to inbreed/line-breed in the next few generations.

Age

Your buck should really be well beyond the adolescent period (probably at least 10 months) unless you are very confident of the temperament of the line he is from. This way you can be sure of his temperament before reproducing it. Your doe should ideally be around 6 to 10 months; old enough to be physically mature, while young enough to cope with the demands of birth and motherhood with less risk of problems occurring. It does seem to be the experience of a number of breeders that both infertility and birthing problems increase with the age of the doe. However, breeding from very young does prior to maturity may help to select for infertility and might not be in the best interests of the line overall. If a line matures so early as to need to be mated by 4 months to be fertile, the chances of it also being very long lived are diminished.