How long does it take for a rabbit to finish giving birth?

Abstract

A 4-year-old female dwarf lop rabbit was presented with dystocia after mis-mating. Abdominal palpation, vaginal examination, and radiography confirmed that the doe was carrying 3 kits. Treatment for the dystocia consisted of gentle manual extraction of the fetuses and fetal membranes, and administration of oxytocin and calcium borogluconate.

Résumé

Dystocie chez un lapin (Oryctolagus cuniculus). Une lapine Bélier nain âgée de 4 ans a été présentée avec une dystocie après un mauvais accouplement. Une palpation abdominale, un examen vaginal et une radiographie ont confirmé que la lapine portait 3 petits. Le traitement de la dystocie a consisté en une extraction manuelle prudente des fœtus et des membranes fœtales et l’administration d’oxytocine et de borogluconate de calcium.

(Traduit par Isabelle Vallières)

A 4-year-old female dwarf lop rabbit with dystocia was presented as an after-hours emergency. The owner had called the emergency line and provided the following history: 2 d earlier, the rabbit had begun nest-building and a bloody vaginal discharge had begun the following day. The owner was unaware that the rabbit was pregnant, but reported the possibility of an accidental breeding with a larger mixed-breed rabbit approximately 1 mo ago. The day the owner called the veterinary clinic emergency line the doe was noted to be calm, but inappetant, with a swollen vulva and persistent bloody discharge. The owner had administered a portion of a 50-mg tablet of dimenhydrinate (Gravol; Church & Dwight Co., Montreal, Quebec), equating to roughly 3.1 mg of dimenhydrinate on the assumption that it would help relieve some of the doe’s discomfort. The owner was advised to bring the rabbit to the clinic.

Case description

On presentation the doe was calm, alert, and responsive but straining, and had an edematous vulva, and bloody vaginal discharge. Strong femoral pulses were palpated; mucous membranes were pink and moist with a capillary refill time of < 2 s. On abdominal palpation, a fetus was palpated and manipulated into the pelvic canal to aid in manual extraction. Flunixin meglamine (Flunazine; Vétoquinol, Lavaltrie, Quebec), was administered subcutaneously at a dose of 1.1 mg/kg body weight (BW) for its anti-inflammatory and analgesic effects. Digital examination of the vagina was conducted using copious amounts of sterile lubricant (Lubricating Jelly; Health Care Plus, Toronto, Ontario). The fetus was determined to be in an anterior longitudinal presentation, dorsal position; and in an abnormal posture with ventral flexion of the head. On the first attempt at manual removal of the fetus, small friable pieces of its jaw and skull were extracted and the fetus was determined to be partially macerated. With continued manipulation of the fetus transabdominally, a lubricated Carmalt forceps was used to carefully grasp the vertebral column of the fetus, and the remaining intact body of a large lightly haired fetus was slowly extracted using gentle posterior-ventral traction. Based on the history, clinical signs, and large size of the fetus, the primary differentials for dystocia were fetal oversize and secondary uterine inertia. At this time the doe was sniffing and her heart rate was within normal limits (280 beats/min; normal range: 130 to 325 beats/min) (1).

Upon further abdominal palpation, another fetus was discovered and medical treatment for dystocia and uterine inertia was instituted, consisting of 4.4 mL of calcium (calcium borogluconate 23%; Vétoquinol), 2.0 mL of Glycol-P (propylene glycol oral solution; Vétoquinol) and sterile water to make a 10 mL solution administered orally with a syringe and teat cannula (J-12 Teat Infusion Cannula; Jorgensen Laboratories, Loveland, Colorado, USA). The doe was placed in her own cage in a quiet examination room and offered apple slices, which she ate freely. Thirty minutes later, 2 units of oxytocin (Oxytocin; Vétoquinol) were administered in the right lumbar muscle. The doe was able to pass the placenta from the previous fetus as well as 1 smaller dead fetus and attached placenta on her own. Ten minutes later nothing more had passed. A ventrodorsal full body radiograph was taken and a third large fetus was visualized in posterior presentation with an extended posture (Figure 1). Gentle palpation and manual extraction of the fetus followed as above. The placenta was not removed at this time. To aid in expulsion of the placenta, a half-dose of the initial calcium borogluconate, Glycol-P and sterile water solution was repeated and 1 unit of oxytocin was administered. The doe was discharged with 15 mg of enrofloxacin (Baytril; Bayer, Toronto, Ontario) 1 tablet q12h, PO for 10 d. Post-operative instructions were to clean the vulvar area and bedding daily. Future breeding was discouraged and an ovariohysterectomy was recommended at a later date. The current diet consisted of leafy greens, carrots, and free choice pellets (Nutriblend Rabbit Ration; Floradale Feed Mill Limited, Floradale, Ontario). A diet change was recommended to decrease the amount of pellets and begin feeding timothy hay to provide more fiber. Discussion with the owner 3 d after presentation revealed that the doe had recovered well and structures resembling placenta had passed.

Ventrodorsal radiograph of the doe revealing 1 remaining fetus (arrow).

A Caesarean section was offered on a referral basis but was declined by the owner at initial presentation.

A postmortem examination was conducted on the 3 fetuses. The body weights of kits 1, 2, and 3 were 83, 33, and 70 g, respectively. The external gross morphological findings revealed the larger fetuses (nos. 1 and 3) had black markings on the fur over the head and dorsum. Fetus no. 1 also had meconium staining on its perineum and hindlimbs. The smaller kit (no. 2) did not have any visible hair and had gray skin. Internal findings revealed marked postmortem decomposition in all 3 kits. On gross and microscopic evaluation there was no evidence of fetal malformation or an infectious process. No specific histologic diagnosis was made; however, the time of death was estimated to be at least 24 h prior to delivery. Bacterial culture on the small kit and attached placenta yielded Staphylococcus pseudintermedius 1+ and 2+, respectively. The isolation of S. pseudintermedius in low numbers is not considered significant and was likely the result of environmental contamination.

Discussion

Unlike dogs and cats, the female rabbit has a unique reproductive tract in that it lacks a uterine body and each of the uterine horns has its own cervix that opens directly into the vagina (2,3). There is abundant adipose tissue in the mesometrium and surrounding the ovaries, making identification and ligation of uterine vessels challenging for an ovariohysterectomy or Caesarean section (2,3). Similar to cats and ferrets, rabbits are induced ovulators; however, ovulation occurs 10 h post-coitus in rabbits versus 30 h after copulation in cats and ferrets (2). Gestation ranges from 29 to 35 d, averaging between 30 to 32 d (1–3). Typical litter sizes for smaller breeds and primiparous does are 4 to 5 kits and larger breeds may produce 8 to 12 kits (2). Birth weight also varies with the breed and ranges from between 30 to 80 g (4).

Several days to hours prior to parturition (kindling), the doe will pull fur from her dewlap, abdomen, and flanks to make a nest (2,4). This is considered normal behavior and aids in exposing the nipples for nursing. While the mammary glands rapidly develop in the last week of gestation, milk letdown is usually delayed until after kindling (5). Parturition, as in other species, is staged. The first stage is mainly characterized by inapparent uterine contractions and dilation of the cervix and ends with the rupture of the chorioallantoic membrane (6). The second and third stages involve the expulsion of the fetus(es) and placenta(e). The first and second stages of labor in rabbits occur almost simultaneously as parturition typically lasts 30 min (7). Kits are typically born in the early morning and are considered altricial as they are usually born hairless and helpless with both their eyes and ears closed (2,4).

Dystocia is the inability to expel fetus(es) from the uterus during parturition and may be due to maternal or fetal conditions preventing a normal delivery. Maternal factors may include pelvic, vaginal, or uterine abnormalities, such as small pelvic size and uterine inertia, or may be due to malnutrition, parasitism, obesity, and/or hereditary causes (6,8). Fetal causes include malpresentation, malposition, or malposture, oversize, fetal death, or malformations, such as fetal monsters (6,8). In many species, uterine inertia is the most common maternal cause of dystocia, and may be considered either primary or secondary (6,8). Primary uterine inertia can be defined as gestation beyond its expected length with no progression into stage 2 labor (6). It may be associated with hypocalcemia, obesity, overstretching of the myometrium from large litters, and conversely, inadequate uterine stimulation from small litters (6). Primary uterine inertia occurs less commonly than secondary uterine inertia (9). Secondary uterine inertia, or uterine fatigue, occurs due to exhaustion and lack of myometrial contraction after prolonged attempts to expel an obstructed fetus, which persists following the relief of the obstruction (6,8). Dystocia is not common in rabbits as normal delivery is typically completed within 30 min after onset (2,7,10). Common causes of dystocia in rabbits include obesity, oversized kits, a narrow pelvic canal, or uterine inertia (2,3,10). Indications of dystocia in rabbits include persistent contractions, straining, and bloody or greenish-brown vaginal discharge (2). However, as obstetrical problems are rare in rabbits and parturition is very quick with minimal physical exertion, any indication of labor can be interpreted as a sign of dystocia.

Assistance of a doe presenting with dystocia usually requires gentle manual extraction of the fetuses and their fetal membranes (2). It is important to ascertain the position of the fetuses to aid in the correction of any malpresentation, malposition, or malposture. Abdominal palpation, digital vaginal examination, radiographs and/or ultrasound are useful tools in this measure. Presentation is the association between the long axis of the fetus and the maternal birth canal (9). Anterior and posterior presentations are normal for rabbits (2). Position is the alignment of the dorsal part of the fetus with the maternal birth canal (9); a dorsal-sacral or dorsal position is considered normal and dorsal-pubic or dorsal-ilial positions are abnormal. Posture describes the disposition of the head, neck, and limbs (9). Any flexion of joints or deviations of the head and neck are considered abnormal. Attempts to correct malpostures involve repelling the fetus back into the uterus and working to extend the affected extremity.

Ecbolic agents, such as oxytocin and calcium may be used in the medical management of dystocia. Medical management should not be considered if any cause of birth canal obstruction is present, as uterine rupture is a potential serious complication (6). Oxytocin promotes the influx of calcium into the myometrial cells, increasing the frequency and strength of uterine contractions (6,8). Postpartum, oxytocin is also used to promote uterine involution, control uterine hemorrhage, and assist in expulsion of retained placentas (8). In rabbits, doses of 1 to 3 units of oxytocin can be administered intramuscularly to assist in uterine contraction (2). Calcium gluconate may also be used as an uterotonic agent in combination with oxytocin (6,8). The current recommended treatment for uterine inertia in a doe is oral administration of 5 to 10 mL of 10% calcium gluconate given 30 min prior to intramuscular injection of oxytocin (2). The doe should then be allowed to rest alone in a quiet area or her cage for an additional 30 to 60 min (2). Surgical management, such as Caesarean section or en bloc ovariohysterectomy, is indicated if medical management is unsuccessful or if a fetal or maternal obstruction cannot be corrected (8,11). The prognosis for a doe presenting with dystocia and non-responsive to oxytocin is guarded (2).

In rabbits, prenatal mortality before 3 wk gestation will likely result in resorption of the fetus, whereas fetal death after 3 wk results in abortion (1,2). Stillbirth occurs during the last part of gestation when the fetus is independently viable. Prolonged gestation often results in small litters, usually stillborn, and may contain 1 or 2 abnormally large or abnormal fetuses (1,7). Other possible explanations for mismatch in fetal size include heredity, breed, and delayed implantation or development of a small fetus in utero (9) (Turner PV. OVC, personal communication, 2010). Litters retained longer than 35 d will die in utero resulting in mummification or maceration (7). Fetal loss can occur at gestation days 13 or 23, times at which the placentation changes and when the fetuses can be dislodged, respectively (1). Possible causes of fetal loss include excessively large or small litters, stress, genetic predisposition, dietary imbalances, heat, trauma, drug use, infection (listeriosis, pasteurellosis, salmonellosis, aspergillosis, chlamydial, and staphylococcal infection), and systemic disease (1,2). Infection with Listeria monocytogenes is an important differential diagnosis in rabbits with late-term abortion as the gravid uterus is a predilection site for replication of the organism and pregnant does are more susceptible to the disease (2,5). Isolation of the organism may be difficult and special enrichment or selective procedures are required (5).

In this case, the owner administered dimenhydrinate to the doe prior to presentation. Dimenhydrinate is primarily used as an antiemetic in dogs and cats, as well as humans; however, as rabbits do not vomit its use was not indicated. Also dimenhydrinate was unlikely to result in fetal loss in this case as the doe was showing signs of dystocia prior to its administration. The 3 kits in this litter were considered to be stillborn based on evidence of fetal distress (meconium staining) and histologic findings. Since the exact breeding date was not known and the litter contained 2 abnormally large lightly haired kits, the most likely cause of the stillborn litter is prolonged gestation (7) (Turner PV. OVC, personal communication, 2010). If this doe had been admitted promptly at the first indication of dystocia (bloody vaginal discharge) perhaps the prognosis for the 3 kits would have been better.

Rabbits are popular pets and will be seen by the small animal practitioner. Special considerations must be made for this species, such as nutritional needs and choice of medications, especially antibiotics. Fiber plays an important role in stimulating normal peristalsis and helps maintain proper dental occlusion (2). A rabbit diet should consist of good quality grass hay, such as timothy hay, and a small amount of a high-fiber (18% to 24%) commercial diet with protein levels around 15% (2,4). Discharge instructions for this doe included a recommendation to add hay to the current feeding regimen. Gastrointestinal dysbiosis may occur following oral administration of gram-positive and anaerobic spectrum antibiotics resulting in overgrowth of enterotoxic Clostridium spp. (2,12). Fluoroquinolones, trimethoprim-sulphonamide combinations, and aminoglycosides are considered safe; however, penicillins, cephalosporins, lincosamides such as clindamycin and lincomycin, and macrolides such as erythromycin, should be avoided in rabbits.

Acknowledgments

The author thanks Drs. Jennifer McConnell and Patricia Turner for their guidance and editorial assistance, Dr. Emily Martin for her consultation on this case, and Dr. Bob Friendship for the final editorial contribution to this manuscript. CVJ

Footnotes

Ms. Dickie will receive 50 copies of her article free of charge courtesy of The Canadian Veterinary Journal.

Use of this article is limited to a single copy for personal study. Anyone interested in obtaining reprints should contact the CVMA office (gro.vmca-amvc@nothguorbh) for additional copies or permission to use this material elsewhere.

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