Introduction

On 30 September 1991, a female killer whale (Orcinus orca) was born at the Vancouver Public Aquarium. Despite excellent nursing behavior, the calf displayed no discernible weight gain over the first two weeks of life. Because Bjossa, the sixteen-year-old mother, had exhibited insufficient milk production with a previous calf, Domperidone (motilium) was administered for ten days in an attempt to enhance lactogenesis. By day twenty-one, however, it was apparent that the calf was losing weight. On day twenty-five, the calf was separated from its mother and a hand-rearing program was initiated.

Logistics of the Hand-Rearing Program

Although the decision to separate the calf was difficult, once made, there ensued a rapid mobilization of resources and support personnel to undertake hand rearing. Formula components and equipment were obtained, stringent formula preparation and sanitation protocols were established, volunteer observers were trained and scheduled for around-the-clock observations, and highly-experienced marine mammal care personnel were flown in from Sea World parks in Florida and San Diego to assist in the hand-rearing effort. In retrospect, it seems that the separation between the calf and her mother occurred at the best possible moment: every opportunity was given for successful nursing and maternal care, but the calf was not allowed to slide so far into deficit as to be unrecoverable.

Due to the logistics of feeding-the low water temperatures, the physical difficulties involved with the capture and restraint of a four hundred and forty pound (two hundred kilogram) animal, the need to coordinate large numbers of staff to accomplish each feeding-and in order to provide the formula volumes necessary for maintenance and growth, it was decided that six feedings per day would be appropriate-frequent enough to deliver required fluids and calories to the calf comfortably and without excessive handling. This schedule proved to be functional for staff and seemed to meet the needs of the calf.

The feeding station was the gate channel between a medical pool and a larger holding pool, where personnel could stand to restrain and support the calf while additional staff delivered the formula from the deck area. Blood samples were obtained by inverting the calf in the gate channel, elevating her tail stalk clear of the water, and drawing blood from the ventral side of her left or right fluke. Weights were obtained by swimming the calf into a stretcher and suspending her from a digital scale using a chain hoist.

Everyone hoped the calf would quickly take to a bottle or some other suckling device, and much thought and effort went into fabricating such a device and encouraging the calf to nurse. The calf never responded successfully to these methods, but this was not considered detrimental; in fact, she so readily accepted the feeding tube that most attempts at bottle feeding were discontinued after a few weeks. Staff did encourage calm sessions when the calf could suckle on a diver's hand, and this proved useful as an outlet for the calf's strong suckling response.

Feedings were accomplished using a ten-foot long, 0.75-inch bore, clear, flexible, polypropylene feeding tube. The tube was lightly covered with lubricating jelly and handed to one of the divers, who then passed it down the calf s esophagus into her stomach. A staff person on deck would suck gently on the end of the tube to form a slight vacuum that usually aided the flow of formula. A funnel was then attached to the tube and the formula was delivered via gravity flow. With this technique, flow rate could be adjusted by lifting or lowering the funnel. An entire feeding-from tube insertion until tube withdrawal-usually lasted less than two minutes.

Immunological Concerns

Serum protein electrophoresis performed on initial blood samples showed extremely low levels of gamma globulin. As a consequence, the entire hand-rearing effort was overshadowed to some degree by concerns about the immune competence of the calf. Although a hyperimmune serum had been prepared in the event hand rearing became necessary, further consultation with immunologists led to the decision not to attempt infusion because of the questionable benefits that might be conferred by the small amount of serum available, and because of the risk of anaphylaxis. Given the uncertain status of the calf s immune system-and following considerable debate-it was decided that it would be prudent to administer prophylactic antibiotics. Baytril (enrofloxacin) was prescribed at a dosage of 5 mg/kg b.i.d. Ile plan was to continue enrofloxacin prophylaxis until the gamma globulin reached protective levels. Although no yeasts or fungi were detected from initial blowhole and rectal cultures, 1,500,000 I.U. of Nilstat (Nystatin) was administered q.i.d. to guard against candidiasis. Systemic antifungal medications were not used due to their potential for toxicity, especially in neonates.

Formula Composition and Analysis

The initial formula was drawn from a highly successful pinniped formula that had been used at Sea World of California. The base for the formula was Multi-Milk^TM (Pet-Ag, Inc.), with cod liver oil serving as a supplementary fat source. This formula was subjected to sophisticated laboratory analysis and was refined and altered to more closely approximate killer whale milk. Formula alterations and additions were made only when clearly definable deficiencies or imbalances were determined. For instance, the amino acid taurine, which is essential in preventing cardiomyopathy in cats, is found in high concentrations in killer whale milk. Taurine was therefore added to the formula. Vitamin supplementation was included when calf blood results were indicating a possible vitamin C deficiency. And, in response to concerns over the potential for vitamin A and D toxicity through the use of cod liver oil, a change to salmon oil was made to provide a more appropriate source of dietary fat.

Fish was not included in the formula until the calf was seventy-one days old, in an attempt to avoid introducing indigestible food material and enteropathogenic microorganisms.

Two problems surfaced that seemed related to the diet: an initial elevation in blood urea nitrogen, and a persistent elevation in serum cholesterol. Laboratory analysis of milk samples taken from a lactating killer whale at Sea World of California showed a rather specific ratio between calories derived from fat and calories derived from protein. The percentage of calories from protein in the killer whale milk samples was in the 12%-13% range. In the initial formula, the ratio of protein calories was about 17%. Clearly, the rise in BUN was directly attributable to excessive levels of dietary protein. Routine biochemistry tests also showed a concomitant rise in creatinine, total protein, and glucose, but there were no other apparent problems and the calf was gaining weight. The quantity of Multi-Milk^TM was therefore reduced and the salmon oil level increased to adjust caloric proportions. A dramatic reduction in the blood urea nitrogen 38 mmol/L to 18 mmol/L-was observed within three days of these component modifications; within seven days, BUN, creatinine, total protein, and glucose levels were within normal parameters.

The cholesterol problem was more mysterious and quite difficult to control. For reasons as yet undetermined, the calf s plasma lipid levels were high initially and climbed continually over the first month on the formula. Plate chromatography of the salmon oil-which had been kept unrefrigerated in an oxygen atmosphere-found significant amounts of free and partial glycerides suggesting probable oxidative degradation that could likely contribute to the hypercholesterolemia. Additionally, a comparative analysis of the sera of the calf and the two adult killer whales at the Vancouver Aquarium showed distinct differences in circulating fatty acids: the profile for the calf was quite uncharacteristic of the species. On 26 November 1991, the calf s total cholesterol had reached 22.4 mmol/L and triglycerides were up to 4.6 mmol/L. Although not of immediate concern, hyperlipidernias in other species can adversely affect organ and cell function, and immune system development.

To resolve this situation, the salmon oil was refined-filtered and cleaned-to remove free fatty acids and oxidants, and was stored in small containers, overlaid with nitrogen, and sealed. Supplementation was made to the formula with nutrients essential for the metabolism of fat and for general nutrition. Carnitor (levocarnitine), which has, in some cases, been effective in reversing complications associated with impaired fat utilization in human infants, was included in the formula. It was thought that this product would prove beneficial to the calf, which was deriving a high percentage of its energy from fat and which may have been experiencing an impaired ability to metabolize fat properly. Although Multi- Milk^TM is fairly high in choline, lecithin was added to help further reduce plasma lipid levels.

After these measures were implemented, modest reductions in plasma cholesterol levels were noted over a six-week period, and were declining consistently until the calf s death. Plasma cholesterol and triglyceride levels from the calf s next to last blood sample, taken on 2 January 1992, had decreased to 11.8 mmol/L and 2.89 mmol/L, respectively.

The final formula, prior to the incorporation of fish, is listed below:

Four batches of this mixture made a twenty-four hour supply of formula.

Upon analysis, this formula broke down to 18.3% fat, 6.4% protein, 73.5% moisture, 0.8% carbohydrates, and 1.0% ash, and yielded 199.8 kcal/100g, or about 2 kcal/g of formula. (Whenever the formula was altered or supplemented, an effort was made to maintain this caloric value of approximately 2 kcal/g).

On an average daily intake of close to twelve and a half liters of formula-with an additional three liters of water provided each day to achieve proper formula consistency and to maintain hydration-the calf was taking in slightly over 25,000 kilocalories per day. The calf gained one hundred and forty-four pounds over a sixty-three day period while on the formula-approximately two and a quarter pounds, or about a kilogram, per day-so it can be determined that 25.1 kilocalories were required to produce a one gram weight gain. (An interesting note: California sea lion pups raised on a Multi-Milk-based formula at Sea World of California, growing at a normal rate, required 24.3 kilocalories to produce a one gram weight gain). Signs of formula intolerance or digestive problems were not observed at any time.

One hundred grams of ground whole herring was introduced into the formula on 10 December 1991; this quantity was then doubled weekly. On 27 December 1991, two small whole herring were placed in the calf s mouth and pushed gently down her throat. The calf tolerated this procedure well and after a few days was readily swallowing the fish on her own. Just prior to death, the calf was receiving 3.2 kg of herring blended into the formula and 500 g of whole herring. A carefully planned weaning schedule was laid out that would have had the calf completely weaned onto fish by the middle of February 1992. Accommodation was made in the schedule to abbreviate the weaning process in the event the calf adapted to the fish feedings more rapidly than expected or in case she began rejecting the tube feedings.

Calf Physical and Social Development

Every stage in the behavioral development of this calf was predictable-based upon observations of killer whale calves in other marine life parks, and through experience gained from previous hand rearing situations-and plans for providing positive interactions and companionship were developed to assist in the physical and social development of the calf.

Past situations have shown that significant advantage can be derived from providing a range of surrogate relationships to an animal that has been removed from the care of its mother. To that end, the calf was placed with an adult female Pacific white sided dolphin (Lagenorhynchus obliquidens). Despite some brief displays of aggression toward the calf, the white sided dolphin generally provided adequate social and physical stimulation.

Early on, efforts were directed at developing some sort of useful bond between the calf and her caretakers. At first, divers were assigned to float passively around the small medical pool, and later, to initiate contact in hope that the calf would respond favorably to the interaction. These attempts were fruitless, but the implementation of more active capture methods eventually conditioned the calf to accept, and eventually to solicit, human contact at feeding time. This mutually beneficial bond evolved productively over several weeks, until divers were spending nearly an hour in the water with the calf after each feeding session.

The entire hand-rearing process was geared toward returning a weaned, healthy calf back to Bjossa, so that she could continue the rearing process and teach the calf appropriate killer whale behavior.

Death and Postmortem Findings

By all outward appearances, and even through diagnostic test results, the calf appeared to be thriving. However, on the morning of 4 January 1992, she suddenly developed nervous symptoms and seemed to be experiencing pain. These symptoms worsened markedly by late afternoon when the calf became disoriented and began colliding with the pool walls. Dexagen-5 (dexamethasone) and Banamine (flunixin meglumine) were administered, and other supportive efforts were made, but the calf's condition continued to deteriorate rapidly. She died at 10:30 p.m.

The only significant postmortem finding in the calf was confined to the brain. Upon removal of the calvarium, a large quantity of whitish-yellow pus readily escaped and caused notable collapse of the brain. There was a very severe acute to subacute suppurative meningitis and multifocal necrotizing encephalitis with multiple bilateral cerebral abscesses. Aspergillus fumigatus was cultured from the purulent material. The diagnosis listed meningitis, meningoencephalitis, and ventriculitis secondary to Aspergillus infection. The route of infection was most likely hematogenous. No site of infection was identified in any of the other organs. Additional organ, tissue, and blubber samples were harvested and wait additional testing.

Acknowledgments

The Vancouver Aquarium offers its gratitude to all staff and volunteers who participated in this effort. Special thanks are extended to Mr. Brad Andrews and Dr. Jim McBain for contributing the full resources of Sea World to the care of the calf, and sincere appreciation goes to Mr. Robin Friday of Sea World of Florida for his remarkable dedication and skill.