Nutritional Status in Captive Bottlenose Dolphins (Tursiops truncatus)
American Association of Zoo Veterinarians Conference 2001
Kerri Slifka1, MS; Susan Crissey1, PhD; Stephen Kahn2, PhD, DABCC; Ann Moser3; Tai C. Chen4, PhD; Jeffrey Mathieu4, MS; Michael F. Holick4, PhD, MD
1Daniel F. and Ada L. Rice Center for Conservation Research, Chicago Zoological Society, Brookfield, IL, USA; 2Loyola University Medical Center, Maywood, IL, USA; 3Kennedy-Krieger Institute, Baltimore, MD, USA; 4School of Medicine, Boston University, Boston, MA, USA


Nutritional status of captive dolphins (Tursiops truncatus) was examined using biochemical analysis. Voluntary blood samples (obtained from four healthy, captive bottlenose dolphins at Brookfield Zoo) were analyzed for vitamin D metabolites [25(OH)D and 1,25(OH)2D], lipids (total cholesterol, triacylglycerides, HDL-cholesterol, and LDL-cholesterol), and fatty acids. Fish fed to these dolphins were analyzed for dry matter, crude protein, fat, energy, vitamin D, cholesterol, and fatty acids. Plasma values for 25(OH)D were higher than those published for a variety of cetacean species, but similar to published bottlenose dolphin data. Total cholesterol was lower than that reported for captive beluga, but similar to wild beluga. Palmitic, oleic, eicosapentaenoic, and docosahexaenoic acids were high in both dolphin plasma and the fish sampled. Vitamin D in herring was similar to that found in other species of fish and was reflected in the high circulating levels of 25(OH)D. Capelin was found to be considerably lower in vitamin D than other species of fish. Total cholesterol in fish samples was higher than that of fillets of other fish species.


Determinations of circulating levels of vitamins, lipids, and fatty acids can provide a base for examining nutritional status of captive cetaceans.9 Limited information exists regarding circulating concentrations of these nutrients in cetaceans. This study examines vitamin D metabolites, lipids, and fatty acids in captive bottlenose dolphins and relates those values to the fish they consumed.



Voluntary blood samples were collected from two male (17 and 19 years) and two female (18 and seven years) bottlenose dolphins at Brookfield Zoo. Both females were gestating at the time blood samples were obtained. Animals were housed in their usual exhibit and fed their usual fish diet with supplemental thiamin, vitamin E, and a multivitamin. Venous blood was drawn by animal management staff into tubes containing either heparin or EDTA and chemically analyzed. Plasma was separated by centrifugation and frozen for less than two months at -80°C until thawed for analysis. Samples from all four animals were analyzed for fatty acids. Samples for vitamin D metabolites and lipids were not obtained from the seven-year-old female.

Samples were analyzed for the vitamin D metabolites 25(OH)D and 1,25(OH)2D at Boston University School of Medicine (Boston, MA). The 25(OH)D was extracted from 0.05 ml plasma with 100% ethanol, followed by a protein-binding assay using rat serum vitamin D-binding protein which has a high affinity for 25(OH)D and using a high specific activity [3H]25(OH)D3 as a tracer.6 To determine 1,25(OH)2D, 1.0 ml of plasma was extracted with acetonitrile. The extracts were then applied to C-18-OH reversed-phase cartridge to separate 1,25(OH)2D from 25(OH)D and tri-hydroxylated vitamin D metabolites. The quantitation of 1,25(OH)2D was accomplished by a radio-receptor binding assay using calf thymus receptor and high specific activity [3H]1,25(OH)2D.3,7

Total cholesterol1,4 triacylglycerides, high-density lipoprotein cholesterol (HDL-cholesterol), and low-density lipoprotein cholesterol (LDL-cholesterol)4 concentrations were measured at Loyola University Medical Center (Maywood, IL) using the Synchron Delta CX7 Analyzer (Beckman-Coulter, Inc., Brea, CA).

Fatty acid analyses were conducted at the Kennedy Krieger Institute (Baltimore, MD). Fatty acids were determined by capillary gas chromatography of fatty acid methyl esters as described by Moser et al.14


Proximate analysis of whole capelin (Mallotus villosus) and herring (Clupea sp.) was conducted at the Brookfield Zoo Nutrition Laboratory. Fish were pureed with liquid nitrogen until they formed a fine powder, then dried at 60°C using a forced-draft oven. Crude protein was determined using the Kjeldahl method ×6.25.2 Crude fat was determined by Soxhlet ether extraction and energy by bomb calorimetry (Parr Instruments, Moline, IL). Vitamin D, cholesterol, and fatty acid analyses of fish were performed by Covance Laboratories (Madison, WI). Vitamin D was determined by HPLC using AOAC method 45.1.22, modified 2. Total cholesterol was analyzed according to AOAC method 994.102. Fatty acids were determined by gas chromatography according to the American Oil Chemists Society.3

Results and Discussion


Vitamin D metabolite, lipid, and fatty acid concentrations in bottlenose dolphin samples are listed in Table 1. There was little variation among dolphins in the concentrations of vitamin D metabolites. Plasma concentrations of 25(OH)D in Brookfield Zoo dolphins were similar to those published for wild bottlenose dolphins.11 Values were higher than published values for wild beluga whales (Delphinapterus leucas), wild pilot whales (Globicephala malaena), and wild white-sided dolphins (Lagenorhynchus acutus).11 Concentrations of 1,25(OH)2D have not been reported in cetaceans. Total cholesterol and HDL cholesterol showed less individual variation than did triacylglycerides and LDL cholesterol. Total cholesterol was lower than previously noted for captive beluga8 but within the ranges obtained for wild beluga.8 No data published for other cetaceans were found.

Table 1. Circulating concentrations of vitamin D metabolites, lipids, and selected fatty acidsa in the plasma total lipids of captive bottlenose dolphins

Vitamin D metabolites and lipids

 Mass percentage of fatty acids

Vitamin D metabolites 

Saturated fatty acids



25(OH)D, ng/ml



Myristic 14:0


1,25 (OH)2D, pg/ml


Palmitic 16:0
Stearic 18:0
Arachidic 20:0



Monounsaturated fatty acids





Total cholesterol, mg/dL








Oleic 18:1ω9


Triacylglycerides, mg/dL


Gondoic 20:1ω9


HDL-cholesterol, mg/dL




LDL-cholesterol, mg/dL


Nervonic 24:1ω9



Palmitoleic 16:1ω7


Vaccenic 18:1ω7


Fatty acid totals, % 

Polyunsaturated fatty acids 






Total saturated fat









Linoleic 18:2ω6


Total ω9


Arachidonic 20:4ω6


Total ω7


Alpha linolenic 18:3ω3


Total ω6


Eicosapentaenoic 20:5ω3


Total ω3




Total fatty acids (µg/ml)


Docosahexaenoic 22:6ω3



Palmitoleic 16:1T


aFatty acids that exceeded 1% were listed.

Monounsaturated and polyunsaturated fatty acid percentages in dolphin plasma were similar at 36% and 38%, respectively, with saturated fatty acids accounting for roughly 20% of the total. Fatty acid composition of dolphin plasma was similar to that previously published for captive bottlenose dolphins15 with oleic, eicosapentaenoic, and palmitic as the three highest fatty acids for both groups. Omega 3 and omega 9 fatty acids made up more than 50% of the fatty acids measured.


Composition of fish is known to vary with species, gender, age, season, and the location where they are caught.5 Nutrient composition of the capelin and herring fed to Brookfield Zoo dolphins on a dry matter basis (DMB) is presented in Table 2. Protein content was similar between the fish types; however, fat content was higher in herring. Vitamin D content of the herring was higher than that for capelin. Fish liver oils are known to be a good source of vitamin D, yet few studies have examined vitamin D content of whole fish. Published values for Baltic herring fillets with skin had higher levels of vitamin D than the herring sampled in this report (3828 IU/100 g and 1257 IU/100 g, respectively DMB). Fresh water perch fillets without skin had lower levels of vitamin D (326–1527 IU/100 g DMB) than the Baltic herring, with an upper range similar to the sampled herring.13

Table 2. Selecteda nutrient composition of fish fed to Brookfield Zoo dolphins on a dry matter basis




Dry matter, %



Crude protein, %



Crude fat, %



Energy, kcal/g



Vitamin D, IU/100 g



Cholesterol, mg/100 g



Saturated fatty acids, g/100 g








Capric 10:0



Myristic 14:0



Pentadecanoic 15:0



Palmitic 16:0



Stearic 18:0



Monounsaturated fatty acids, g/100 g




Palmitoleic 16:1



Oleic 18:1



Eicosenoic 20:1



Polyunsaturated fatty acids, g/100 g







Linoleic 18:2



Linolenic 18:3



Octadecatetraenoic 18:4



Eicosapentaenoic 20:5



Docosapentaenoic 22:5



Docosahexaenoic 22:6



Saturated fat, g/100 g



Polyunsaturated fat, g/100 g



aFatty acids that exceeded 0.05 g/100 g were listed.

Total cholesterol in capelin was higher than the herring. Lie et al.12 examined the fatty acid and cholesterol content of a variety of fish species but analyzed fillets, not whole fish. Cholesterol of the sampled fish was twice that of the fish fillets examined by Lie, which was to be expected.

Myristic, palmitic, palmitoleic, oleic, eicosenoic, eicosapentaenoic, and docosahexaenoic acids were the highest in both herring and capelin. Eicosenoic was highest in capelin, while palmitic was highest in herring. Overall, herring had higher levels of both saturated and polyunsaturated fatty acids. Palmitic and oleic acids were high in many fish species examined by Lie et al.,12 as it was in the sampled fish. However, herring and capelin were considerably higher in eicosenoic acid compared to most species reported.

Plasma concentrations of vitamin D metabolites, lipids, and fatty acids in captive bottlenose dolphins appear to be reflective of the fish diet consumed. The supplemental multivitamins contributed to the vitamin D concentrations in plasma but were consumed at such low levels that the impact should not have been substantial. Diet was noted as the primary factor for difference found in the fatty acid composition of the liver of freshwater and marine ringed seals.10

Literature Cited

1.  Allain CC, Poon LS, Chan CSG, Richmond W, Fu PC. Enzymatic determination of total serum cholesterol. Clin Chem. 1974;20:470–475.

2.  AOAC. Official Methods of Analysis of AOAC International. 16th edition. Arlington, VA: AOAC International; 1995.

3.  American Oil Chemist’ Society. Ce 1–62 fatty acid composition by gas chromatography. In: Official Methods and Recommended Practices of the AOCS. 5th ed. Champaign, IL: American Oil Chemists’ Society; 1997.

4.  Beckman-Coulter, Inc. Synchron Delta CX7 Technical Procedure Manual. Brea, CA: 1997.

5.  Bernard J, Allen ME. Feeding piscivorous animals: nutritional aspects of fish as food. In: Baer DJ, Crissey SD, Ullrey DE, Baer, eds. Nutrition Advisory Group Handbook Fact Sheet 5. American Zoo and Aquarium Association. 1997.

6.  Chen TC, Turner AK, Holick MF. Methods for determination of the circulating concentration of 25-hydroxyvitamin-D. J Nutr Biochem. 1990;1:315–319.

7.  Chen TC, Turner AK, Holick MF. A method for the determination of the circulating concentration of 1,25-hydroxyvitamin-D. J Nutr Biochem. 1990;1:320–327

8.  Cook RA, Stoskopf MK, Dierenfeld ES. Circulating levels of vitamin E, cholesterol, and selected minerals in captive and wild beluga whales (Delphinapterus leucas). J Zoo Wildl Med. 1990;21(1):65–69.

9.  Crissey SD, Maslanka M, Ullrey DE. Assessment of nutritional status of captive and free-ranging animals. In: Baer DJ, Baer CK, eds. Nutrition Advisory Group Handbook Fact Sheet 8. American Zoo and Aquarium Association. 1999.

10.  Kakela R, Hyvarinen H. Composition of polyunsaturated fatty acids in the liver of freshwater and marine ringed seals (Phoca hispida spp.) differs largely due to the diet of the seals. Comp Biochem Physiol Part B. 1998;120:231–237.

11.  Keiver KM, Ronald K, Draper HH. Plasma levels of vitamin D and some metabolites in marine mammals. Can J Zool. 1988;66:1297–1300.

12.  Lie O, Lied E, Maage A, Njaa LR, Sandnes K. Nutrient content in fish and shellfish. Fisk Dir Skr Ser Ernaering. 1994;6(2):83–105.

13.  Mattila P, Piironen V, Haapala R, Hirvi T, Uusi-Rauva E. Possible factors responsible for the high variation in the cholecalciferol contents of fish. J Agric Food Chem. 1997;45(10):3891–3896.

14.  Moser AB, Jones DS, Raymond GV, Moser HW. Plasma and red blood cell fatty acids in peroxisomal disorders. Neurochem Res. 1999;24:187–197.

15.  Nelson GJ. The lipid composition of the blood of marine mammals-III. The fatty acid composition of plasma and erythrocytes of Atlantic bottlenose dolphin, Tursiops truncatus. Comp Biochem Physiol. 1973;46B:257–268.


Speaker Information
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Kerri Slifka, MS
Daniel F. and Ada L. Rice Center for Conservation Research
Chicago Zoological Society
Brookfield, IL, USA

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