Concentrations of retinol, 3,4‐didehydroretinol, and retinyl esters in plasma of free‐ranging birds of prey

Abstract

This study investigated vitamin A compounds in the plasma of healthy free-ranging Central European raptors with different feeding strategies. Plasma samples of nestlings of white-tailed sea eagle [white-tailed sea eagle (WTSE), Haliaeetus albicilla) (n = 32), osprey (Pandion haliaetus) (n = 39), northern goshawk (Accipiter gentilis) (n = 25), common buzzard (Buteo buteo) (n = 31), and honey buzzard (Pernis apivorus) (n = 18) and adults of WTSE (n = 10), osprey (n = 31), and northern goshawk (n = 45) were investigated with reversed-phase-high-performance liquid chromatography (RP-HPLC). In WTSE, northern goshawks and common buzzards retinol were the main plasma component of vitamin A, whilst in ospreys and honey buzzards, 3,4-didehydroretinol predominated. The median of the retinol plasma concentration in the nestlings group ranged from 0.12 to 3.80 μm and in the adult group from 0.15 to 6.13 μm. Median plasma concentrations of 3,4-didehydroretinol in nestlings ranged from 0.06 to 3.55 μm. In adults, northern goshawks had the lowest plasma concentration of 3,4-didehydroretinol followed by WTSE and ospreys. The plasma of all investigated species contained retinyl esters (palmitate, oleate, and stearate). The results show considerable species-specific differences in the vitamin A plasma concentrations that might be caused by different nutrition strategies.

Insects as Food for Insectivores

“…It is unclear if 3-hydroxyretinal can serve as a source of vitamin A because it is unknown if 3-hydroxyretinal can be converted into retinal by insectivores. Honey buzzards (Pernis apivorus (L.)) a primarily insectivorous bird, were shown to contain high levels of 3-4-didehydroretinol in their plasma, suggesting insectivorous birds might be able to use some of the atypical retinoids found in adult insects (Müller et al, 2012). Second, because the retinoid levels in fruit fly eyes was a function of dietary carotenoid content, it may be that diets fed to commercially raised insects do not contain sufficient levels or types of carotenoids to optimize the retinol, retinal, and 3-hydroxyretinal content of insects.…”

Effects of feeding on plasma concentrations of vitamin A in captive African penguins (<i>Spheniscus demersus</i>)

“…Consequently, a relatively high concentration of vitamin A 2 is observed in birds and mammals that eat freshwater fish. Retinol is the major vitamin A in the plasma of free-ranging birds that consume marine fish, whereas the plasma 3,4-didehydroretinol concentration is high in free-ranging osprey ( Pandion haliaetus ), which probably eats freshwater fish [17]. The concentration of vitamin A 2 in the liver and adipose tissue was much higher in free-ranging lacustrine seals ( Phoca hispida saimensis and Phoca hispida ladogensis ) than in free-ranging marine seals ( Phoca hispida botnica and Phoca hispida hispida ) [12].…”

“…Hepatic concentration of vitamin A 2 was remarkably higher in American minks (Neovison vison ) fed with freshwater fish than in those nourished with marine fish [13]. On the other hand, the existence of vitamin A 2 has not been reported in penguins, which usually feed on marine fish [17].…”