Vitamin blood concentration and vitamin supplementation in bottlenose dolphins (Tursiops truncatus) in European facilities

Abstract

Background: As fish eaters bottlenose dolphins (Tursiops truncatus) in human care need to receive daily vitamin supplementation, because whole thawed fish lacks certain vitamins. However, the exact concentration of supplementation has not been established and is a matter of discussion. To ensure adequate vitamin supplementation in pets, vitamin blood concentrations are measured. This is not a common practice in dolphins. The objective of the present study was to collect information about vitamin supplementation in bottlenose dolphins and on vitamin blood concentrations of healthy animals in European facilities. In addition, these results were compared with blood levels of wild animals. Conclusions on how to provide bottlenose dolphins in human care with an effective vitamin supplementation will then be drawn. Initially, fish-handling techniques and vitamin supplementation were evaluated by questionnaire, which was sent to 25 European facilities that house bottlenose dolphins. Secondly, blood samples from 57 dolphins living in 10 facilities were taken and sent by mail to a reference laboratory. They were analysed for retinol, thiamine pyrophosphate, cobalamin, calcidiol and tocopherol. The blood concentrations were then correlated with vitamin supplementation, fish handling techniques and pre-existing blood concentrations of free-ranging dolphins. Finally, the data was subjected to a standard analysis of variance techniques (ANOVA) and a linear model analysis.

Results: Fish was mainly thawed in a refrigerator. Further, the 95 % confidence interval for retinol blood concentrations was 0.048 to 0.059 mg/l and for tocopherol 17.95 to 20.76 mg/l. These concentrations were 27 and 53 %, respectively, higher than those found in free-ranging animals. In contrast, calcidiol concentrations (143.9-174.7 ng/ml) of the dolphins in human care were lower than in blood found for free-ranging animals. Regarding thiamine pyrophosphate and cobalamin, concentrations ranged between 0.42 and 0.55 mg/l and 175.55 and 275.22 pg/ml respectively. No reference concentrations for free-ranging Tursiops truncatus were found.

Conclusions: These findings suggest an over-supplementation of retinol (vitamin A) and tocopherol (vitamin E) in bottlenose dolphins (Tursiops truncatus) housed in human care. Therefore, vitamin A supplementation should not exceed 50,000 IU per animal per day and vitamin E supplementation should be around 100 IU per kg fed fish per day.

Keywords: Bottlenose dolphin; Calcidiol; Cobalamin; Fish thawing; Retinol; Thiamine; Tocopherol; Tursiops truncatus; Vitamin blood concentration; Vitamin supplementation.

Fig. 1

Brand names, composition and daily supplier’s recommendation of vitamin supplements used for bottlenose dolphins (Tursiops truncatus) in 19 European facilities. Aquavits © produced by Zoovet Products, IZVG LLP, West Yorkshire, United Kingdom. SeaTabs © produced by Pacific Research Laboratories, Inc., California, United States. Mazuri Fish Eater Tablets ® produced by Mazuri Zoo Foods, Essex, United Kingdom

Fig. 2

Thiamine pyrophosphate serum concentrations of bottlenose dolphins (Tursiops truncatus) in relation to thawing techniques. Box plots comparing thawing techniques in relation to the natural logarithm of thiamine pyrophosphate serum concentrations of bottlenose dolphins (Tursiops truncatus). N = 25 for thawing without running water (thawing in refrigerator, at room temperature), N = 29 for thawing with running water (includes any thawing method that uses running water). Box plots show the range of the mean 50 % of the data. Within the boxes, the thick line indicates the arithmetic mean

Fig. 3

Thiamine pyrophosphate serum concentrations of bottlenose dolphins (Tursiops truncatus) in relation to lactation status. Box plots comparing thiamine pyrophosphate serum concentrations in lactating and non-lactating bottlenose dolphins (Tursiops truncatus). N = 7 for lactating females, N = 47 for non-lactating dolphins. Box plots show the range of the mean 50 % of the data. Within the boxes, the thick line indicates the arithmetic mean. Fifty-four is the number of one dolphin, indicating an outside value