Rabbit breeds of medium to large size are sexually mature at 4 to 4.5 months, giant breeds at 6 to 9 months, and small breeds (such as the Polish Dwarf and Dutch) at 3.5 to 4 months of age. The release of eggs in female rabbits is triggered by sexual intercourse, not by a cycle of hormones as in humans. The rabbit has a cycle of mating receptivity; rabbits are receptive to mating about 14 of every 16 days. A doe is most receptive when the vagina is red and moist. Does that are not receptive have a whitish pink vaginal color with little or no moisture. A veterinarian may be able to feel fetuses in a pregnant doe's abdomen 12 days after breeding. False pregnancy, during which the rabbit shows signs of pregnancy but is not actually pregnant, is common in rabbits.
Pregnancy lasts about 31 to 33 days. Does with a small litter (usually 4 or fewer kits) seem to have longer pregnancies than those that produce larger litters. If a doe has not given birth by day 32 of her pregnancy, your veterinarian may induce labor; otherwise, a dead litter may be delivered sometime after day 34. Occasionally, pregnant does abort or reabsorb the fetuses because of nutritional deficiencies or disease.
Nest boxes should be added to the cage 28 to 29 days after breeding. If boxes are added too soon, they become contaminated with urine and feces. A day or so before giving birth, the doe pulls fur from her body and builds a nest in the nest box.
Rabbit kits are born naked, blind, and deaf. They begin to show hair a few days after birth, and their eyes and ears are open by day 10. Newborn rabbits are unable to regulate their own body temperature until about day 7. The doe can become pregnant again 24 hours after giving birth. Most people raising rabbits for show or as pets rebreed does 35 to 42 days after the birth of a litter.
Most medium- to large-sized female rabbits have 8 to 10 nipples, and many give birth to 12 or more young. If a doe is unable to nurse all the kits effectively, kits may be fostered by removing them from the nest box during the first 3 days and giving them to a doe of about the same age with a smaller litter. If the fostered kits are mixed with the doe’s own kits and covered with hair of the doe, they are generally accepted. Moving the larger kits instead of the smaller kits to the new litter increases the chance of success. Does nurse only once or twice daily, and kits nurse for less than 3 minutes at a time. Kits are weaned around 4 to 5 weeks of age.
Kits can be reared by hand, but the death rate is high. They should be kept warm, dry, and quiet. If a lactating doe is not available to foster the kits, they can be given kitten milk replacer twice a day. Feedings vary from ½ teaspoon to 1 tablespoon, depending on the age and breed of the kits. Domestic rabbit kits are weaned at about 6 weeks old.
Young does may kill and eat their young for a number of reasons, including nervousness, neglect (failure to nurse), and severe cold. Dogs or predators entering a rabbitry often cause nervous does to kill and eat the young. Cannibalism of the dead young occurs as a natural nest-cleaning instinct. If all management practices are proper and the doe kills 2 litters in a row, she should not be used for breeding.