Abstract
Similar to other cetaceans, twins are believed to occur at a rate of less than 1.0% in beluga whales and no reports exist of a twin surviving.4,6 In beluga whales, one case has been reported where an animal aborted naturally conceived twins after approximately 300 days of gestation.3 Twins which occur in typically uniparous species often suffer from retarded intrauterine growth and may not survive due to inadequate organ development.7 The respiratory system is one of the last to mature, and in near term fetuses, the development rate of this system can be increased with antenatal treatment.2 In this report, a 22 year old multiparous female Delphinapterus leucas was artificially inseminated with 524 x 106 progressively motile, frozen thawed semen deposited deep within both uterine horns on 3/27/2008.5 At insemination, the animal had two large follicles with maximum diameters of 1.93 cm and 2.41 cm, respectively, on her right ovary which subsequently ovulated. On day 149 of gestation, twin fetuses were detected via ultrasound examination. Both fetuses were well formed with viable heartbeats. Despite no previous history of successes with twins, it was decided not to interfere (terminate or supplement) with the pregnancy and monitor fetal development and viability. In addition, if gestation reached at least 92% of a normal length or 434 days (based on a normal gestation of 471 ± 10.4 d, 95% CI of 450 to 491 d; n = 8), then antenatal treatment and 24 hour monitoring would be instituted. To address concerns about inadequate fetal lung development, two injections of 12 mg betamethasone (Taylors Pharmacy, Winter Park, Florida) were administered intramuscularly to the cow 24 hours apart starting on day 435 and continuing every 10 days until delivery.2 Labor began 6 days after the first series of injections on day 441, and a live female calf was delivered at 1759 hours on day 442. This calf was 40.9 kg and 139.7 cm in length and was delivered in head-first presentation. A second calf, a 22.7 kg male, was stillborn in fluke-first presentation at 0154 hours on day 443. This calf appeared to have died several days earlier. The first placenta was passed at 0447 hours and the second at 0901 hours. The first placenta was necrotic when passed.
Immediately after birth, the first calf was administered 120 ml of calfactant (Infasurf®, ONY Inc.) intratracheally via a red rubber feeding catheter.1 The total volume was divided into four aliquots. Half of the aliquot was administered with the calf rolled partially to one side and the other half while rolled to the other side. The calf was then released to swim a short while and take several breaths. Then the next aliquot was administered with the pattern repeated. Twenty-two hours post-partum, the calf was administered 65 mg immunoglobulin (Delphinapterus leucas Ig, U.C. Davis, Laboratory for Marine Mammal Immunology) IM, and tubed with 150 ml of beluga formula (SeaWorld cetacean neonate formula) containing 5 mg/kg of enrofloxacin (Baytril®, Bayer HealthCare LLC, Animal Health Division). Antibiotic treatment was continued b.i.d. PO for 10 days. Day 2 post-partum, the calf was given 150 ml of formula by tube at 0830 and 1200 hours and 400 ml at 1530 hours. Day 3, the calf was tubed 5 times with 345 ml of formula (875 ml total) or extracted milk from the cow (850 ml total) every 3 to 4 hours. On day 3, the calf started nursing, so tube feedings were limited to 100 ml formula with antibiotic b.i.d. until day 10. After day 10, the calf continued nursing voluntarily. Bimonthly weight and length measurements demonstrate that after an initial increased growth rate, the calf continues to grow within normal parameters. This calf represents the first known successful surviving twin of any cetacean species and sets an important precedent for treatment modalities that may be available to assist the premature cetacean neonate.
Acknowledgements
The authors would like to thank Brad Andrews, Chris Bellows and all of the SeaWorld San Antonio team members for their support, especially the Animal Care and Training staff, and Brian Kot for the initial ultrasonographic determination of twins.
References
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