Problems Associated with Pregnancy
Fat sows in late pregnancy are especially susceptible to toxaemia. The animals become lethargic, refuse food and usually die within twenty-four hours.
This disease is nutritional in origin and better-quality food will prevent deaths.
Dystocia (Difficulty Giving Birth)
This is not a common cause of mortality in guinea pigs, though it does occur, particularly with large single fetuses. It has been suggested that it is more common in sows that are first mated at six to eight months of age.
This occurs in varying stages of pregnancy. Examination of fetuses has not revealed a common cause though several bacteria have been incriminated. If abortion becomes a common problem it is best to cull the sow.
The most important cause of mortality in the peri-natal period in many colonies is smothering, common in large litters when the sow fails to clean the newborn, and the baby’s nostrils are blocked by the fetal membranes. Prevention can only be by supervision at the time of birth.
Smothering can occur at any age if sudden loud noises occur and they all rush to the far corner of the cage and huddle up to five deep until the threat has passed.
Losses from Injuries in Suckers
Injuries to suckers (baby guinea pigs) are usually caused by adults disturbed by overcrowding. The injuries most frequently are seen as subcutaneous abscesses, often in the thoracic region. Remove some of the adults from the pen to prevent recurrences.
These are rare except where there is gross inbreeding.
Small weak suckers
Runts are seen on odd occasions in litters of all sizes and are associated with feeding poor-quality green food to the sow some two to three weeks before birth. Control is by paying more attention to the diet of the sow.
Farrowing (giving birth) seems to be one of the more common worries by owners, yet it rarely causes problems. Internal palpation is readily done, as the pelvic size is relatively large. Manual delivery can be successful due to the large size of the pelvis.
A good indicator of viability for the mother is that one or more live babies are already out. Where all previous have been dead, manual delivery does not always save the mother. The membranes of the newborn look like small kidneys when passed.
The average litter is three or four young, but depending upon the strain o guinea pigs Iitters may vary in number between one to ten. The first litter of a young female is usually quite small.
The sow at the prime of her reproductive life—from six months of age to four years—can have as many as four or even five litters per year, but if you want strong young you should not allow the sow to bear more than three litters in the year.
Sows come into heat very soon after giving birth—between ten to twelve hours later. Some commercial breeders leave the boar with the pregnant sows so that they can mate during the post-partum heat, but for the home breeder it is best to remove the pregnant sow to her own cage and prevent this post-partum heat mating. This allows her to rest between litters.
From the time the young begin to nurse until they are weaned, the sow will not have other heat periods. Except for the post-partum heat it is usually safe to leave the suckling sow with the boar.
Only in the rarest instances will the boar bother or injure the young. Males have been known to eat the young.
Young guinea pigs (suckers) are born fully haired, toothed and with their eyes open. They begin walking and running within an hour after they are born. In two or three days they begin to eat solid food in addition to nursing from the mother. The guinea pig is communal in its rearing of the young. The sow will allow any sucker in her pen to suckle. However, groups of more than twelve sows (with thirty-five to forty-five suckers) can suffer from overcrowding, with losses due to fighting and starvation. Smaller groups of four to five sows are best. Where a number of sows are having litters it is best to keep the sows with similarly aged litters together.
Some breeders recommend that each cage be provided with a nesting b7 A small box 30 centimeters square with a door through which the guinea pig can enter the main cage area is suitable. It can be made of wood or cardboard, but the top should be removable for easy cleaning.
Growth After Weaning
Suckers should be weaned at eighteen to twenty-one days of age. If they are left any longer, some of the young sows will he mated b y the adult boar.
At weaning time the young should weigh about 250 grams. Growth continues until about eighteen months of age, when the boars will average 25 centimeters in length and about 1 kilogram in weight. The sows. unless pregnant, average slightly less.
Guinea pigs will generally breed up to their fifth year, but after the third or fourth year breeding becomes irregular and litters are smaller. Very few guinea pigs live beyond seven years of age. Five or six years are considered a very full life.