Pf. Surai et al., Effects of piscivory on the fatty acid profiles and antioxidants of avian yolk: studies on eggs of the gannet, skua, pelican and cormorant, J ZOOL, 255, 2001, pp. 305-312
Piscivorous birds consume diets which are rich in highly-polyunsaturated n-
3 fatty acids; these play vital roles in embryonic development but are very
susceptible to oxidative damage. The effects of such diets on the fatty ac
id composition and antioxidant content of the yolk were investigated in the
northern gannet Morus bassanus, the great skua Catharacta skua, the Americ
an white pelican Pelecanus erythrorhynchos and the double-crested cormorant
Phalacrocorax auritus. The phospholipid fraction of the eggs of these four
species contained high proportions of the n-3 fatty acid, docosahexaenoic
acid, which formed 7.5-11.3% (w/w) of the fatty acids of this fraction. The
presence of eicosapentaenoic and docosapentaenoic acids also contributed t
o the total n-3 content of the phospholipid. The n-6 polyunsaturate, arachi
donic acid, formed between 8% and 19% (w/w) of the phospholipid fatty acids
. For the pelican and cormorant, this is consistent with the consumption of
freshwater fishes in which arachidonic acid may be a significant acyl cons
tituent. This finding is, however, more difficult to explain for the gannet
and skua which largely consume marine fish with a low arachidonic acid con
tent. The yolks of all four species contained relatively high concentration
s of vitamin E (90.2-302.3 mug g(-1) wet yolk) which was mainly present as
alpha -tocopherol. The eggs of the pelican and cormorant were especially en
riched in carotenoids (150.9 and 115.7 mug g(-1) wet yolk, respectively).