by Gareth Wild

Created on: July 01, 2010

The gestation period for a guinea pig varies depending on the litter size. It can range from 59 to 72 days. But on average it is referred to as being of 63 days.

In order to get the female guinea pig pregnant she needs to be fertilised during her oestrus cycle which is between 15 to 17 days. During this time she is only receptive for a very short amount of time around 6 to 11 hours. The female spontaneously ovulates.

To obtain the best breeding success the animals should be aged 3 to 4 months for the male and 2 to 3 months for the female. They will be weighing approximately 400g for the female while the male is larger and heavier at 650 grams. The male, the boar, can be housed with up to ten females. Guinea pigs do better when housed with others as the young will be raised by several females when they are housed in a harem system. That is one male with multiple females.

During the gestation period the female will require additional vitamin c as she will increase her need from the usual 5mg/kg daily up to around 30mg, kg once pregnant. This need can be satisfied by offering food with additional vitamin c such as oranges, kale or cabbage.

As the gestation nears the last week the female guinea pig begins to prepare her body for the birth. This is done by her body producing a hormone called relaxin. Relaxin causes the pelvic cavity of the female to expand. The relaxin causes the ligaments in the pelvis to relax allowing the bones to separate at the pubic symphysis. During birth the gap can increase to about 2.5cm. About 24 hours after birth, parturition, the bones return to normal. The main reason you should breed the animals at the 2 to 3 months for the females is due to the fact that the pubic symphysis fuses as the virgin female gets older and the ligaments don’t respond to the relaxin as well, this means that birthing can become more difficult. The latest they should have their first litter is before they reach 7 or 8 months of age, any later than this and the symphysis is unable to separate.  Any later than this and difficulty in giving birth or dystocia will occur. Foetal death is also likely to happen.

The guinea pigs get very large when pregnant and extra care should be taken in handling as incorrect handling can lead to miscarriage. So ensure the hind quarters are fully supported.

The animals can be bred up to about 20 months old after this litter size will begin to decrease and birthing difficulties will  occur at a higher incidence.

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