Evaluation of captive dolphins diet quality as influenced by different factors

Currently diet for captive dolphins is based on raw fish species such as blue whiting (Micromesistius poutassou), capelin (Mallotus villosus) and herring (Clupea harengus L.). After catching they are normally stored for different time before to be fed animals and hence their quality may undergo different biological processes with a consequence of quality deterioration. The aim of the present work is to check the nutritional characteristics of feed used for adult dolphin kept in captivity, with a particular attention to the lipid status. Proximate composition, peroxide value, TBARS and fatty acid profile were determined on frozen blue whiting, capelin and herring, sampled once a month for seven times. Proximate composition were performed according to AOAC method while peroxide value by titration with sodium thiosulphate and TBARS accordingly with Schemedes and Holmer. Finally fatty acid profile was obtained by gaschromatography analysis. A wide range of variations in proximate composition and lipid quality has been demonstrated between and within species. In comparing proximate composition, the main variations are related to lipid content with the lowest value (1.50g 100g-1) for blue whiting and a very fluctuating value for herring (from 4.1g to 16.5g 100g-1). Even more pronounced is the variability in lipid status indicating the presence of toxic molecules such as free radicals and other secondary products of lipid oxidation (range of peroxide value: 4.12 – 119 meq O2 Kg-1 grasso and MDA: 60 – 6527 nmol g-1). In conclusion it should be noted that along with a different energy content as a consequence of fish species and batch of catches, lipid quality can be strongly affected by storage; this fact should be taken in due consideration in dolphins husbandry.