Pregnancy and birth

Once you have chosen your breeding pair, you will obviously have to choose how and when to put them together in order for pregnancy to result. At this stage your doe should generally be around 6-10 months old (for a first litter) but this is where it pays dividends to know as much as you can about the lines your chosen rats are from, and their specific variety. Some lines seem to mature very early and lose fertility early; does from these lines may be ready for mating by around 4 months, but bear in mind that the later you mate them the more you will select for fertility. Unless the lines are well proven for temperament and you know them intimately, it is wise to at least allow your buck to get past adolescence to ensure that his temperament remains steady and unproblematic. The less you know about your buck's line, the later you should probably leave it before using him. Around the end of his first year is a good time (10-12 months), when his fertility and interest are still assured, but any temperament problems will have shown - though most male hormonal agression shows itself well before this age. Do not assume that every rat you acquire (or keep) for breeding will 'make the grade'.

On the whole the most efficient way to allow two rats to mate is to simply watch the doe until she is on heat (usually in the evening), and then leave her and the chosen buck together, in a plain smallish cage with food and water, overnight. This way you can accurately predict the due date. Count day 1 as the day following the evening when you put them together. The litter will generally be born on day 22 or (more often) 23. Some does are hard to spot 'in heat', in which case you can simply try the pair together for a few minutes each evening. If the doe is not on heat she will be unreceptive to the bucks advances and will tend to karate kick him away using her back legs. You will immediately notice the difference when she is on heat, as she will not only become receptive to his interest but will encourage him, and is likely to begin to dart and jump about the cage, presenting herself for mating. One trick to encourage a doe into heat is to place her in a cage that has been previously occupied by does that she doesn't normally live with. Leave her in there for an hour or two and then add the buck. Often this is sufficient to bring a doe into heat.

The morning after the night of mating you can place both rats back in with their cage-mates. Once mated, never leave the buck in with the doe until the time of birth, as does become receptive again within 24 hours of giving birth and can easily become pregnant again at this time. Now all you have to do is wait, though if you have accurate scales the quickest way to 'diagnose' pregnancy is by weight gain. I don't weigh my does as I have always found them easy to assess - on the whole within a week they feel much denser around the back end, and soon become noticeably heavier to the hand and eye. By the end of the second week, not only will they be gaining a round belly, but they will begin to lose a ring of hair from around their nipples, so that over the third week these begin to look more prominent.

In the final week, weight gain is usually very obvious, as the doe takes on a pear like appearance. She may begin building nests around the cage, and may also become more touchy with her rattie friends. If this grouchiness is excessive she can be removed from her cage mates into a nursery cage. However many does seem to prefer the company and familiarity of their friends until closer to their due date. I normally remove the doe to a freshly cleaned suitable cage of her own on day 21 (unless there has been a need to separate her before this). I use Ecopetbed (shredded card) as cage litter and I also give the doe a handful of Safe Bed (soft shredded paper). Other than that the cage is initially empty, apart from a food dish and a water bottle. I have found that all does are capable of making whatever degree of nest they feel they require to seclude their babies in. You may want to use an igloo but I have found that igloos have several disadvantages; they increase condensation and dampness of the nesting materials which makes a nice breeding ground for bacteria, and may decrease mother and baby comfort; they make access to the nest without disturbing it somewhat more difficult; they give the growing babies somewhere to 'flee' to - which I have repeatedly found makes them less confident and outgoing as they age. Left to their own devices some mums just birth on the flat bedding and then build a nest around their babies (though never hide them away from sight). Other mums build a large, spectacular nest and tunnel entrances.

Do not give the doe a hammock at this stage - the babies will remain in the nest so she needs only to leave the nest to get away from them. I stopped using hammocks after I had one doe who decided to birth in hers. This was very messy and the blood pooled allowing the babies to get wet and cold. Happily I was at home and was able to intervene and clean up the mess. Another issue with hammocks is that sometimes the doe leaves the nest with a baby or two clinging on to her teat. If a baby ends up being 'dropped' in the hammock it could be left there and unable to return to the nest itself.

The onset of labour is heralded by some minor spotting of blood. If you see this and nothing happens (over the next few hours) this may indicates that labour is not progressing. This can be due to low levels of the hormones that maintain labour, and in such cases an injected dose of oxytocin may help. Some labours simply do not progress* and if the doe is not bleeding heavily the best course of action (if oxytocin has failed) is often best to allow nature to take its course. Usually dead babies are passed 2 or 3 days later. A caesarean section (CS) is possible in a rat but almost never yields live babies, so should be seen as a life saving treatment for the doe. Uterine inertia (failure of the uterus to contract properly) is occasionally life threatening, so one has to weigh the risks involved in an anaesthetic. Bear in mind there may be increased risk factors such as blood loss, deranged blood levels of electrolytes (as would be seen in toxaemia of pregnancy) and exhaustion.

*Possible causes of uterine inertia are stress (due to disturbance, presence of predator etc), poor nutrition, low blood sugar, hormone imbalance (commoner in the winter as the raised levels of melatonin produced during the longer hours of darkness inhibits the production of some reproductive hormones), disease (e.g. rat Parvovirus).

Occasionally labour fails to progress because a baby is stuck in the birth canal. In this case a CS might be necessary, and may actually save some of the babies. I have never heard of a mother who was able to lactate and feed her own babies after a CS, so a foster mother would need to be found for any live babies. For fostering to be successful, the mother would need to have young eepers of her own, probably under a week old.

The other major birthing problem is haemorrhage. This is often due to separation of the placentas from the uterine wall before it is appropriate. In this instance the babies cannot be saved. Blood loss itself can be life threatening but surgery following severe blood loss will often hasten death, so it may be best (following veterinary advice) to offer supportive treatments. Fluids can be given subcutaneously, and a vitamin K injection may help to stop bleeding. Warm oral fluids should be offered from a 1ml syringe (adding something like glucose or Dr Squiggles can increase intake) very frequently initially. It is also important to keep the doe warm (a thermostatically controlled heat pad is best for this), quiet and free from further stress.

Happily, most rattie labours happen without event and from the onset of the first spotting babies are normally delivered within a couple of hours. The doe will clean the babies as they arrive (and eat the placentas and birth sacs), but occasionally if the babies are born very quickly a doe can get into a bit of a mess at this stage and may need a little help detaching placentas etc. Be sure that your mentor is aware of your rat's due date. Hopefully you will be able to contact them at any time if you run into problems.