Differences in egg lipid and antioxidant composition between wild and captive pheasants and geese

The aim of this study was to assess the differences in yolk lipid compositi on of pheasants and geese between birds maintained in captivity on commerci al grain-based diets and their counterparts in the wild which are free to s elect their diets from the environment. The most striking difference was th at the proportion of a-linolenic acid (18:3n-3) was far greater in all yolk lipid classes [triacylglycerol (TAG), phospholipid (PL), cholesteryl ester (CE)] of the wild birds than in the captive birds of both species. For exa mple, in yolk TAG, the level (wt.% of total fatty acids) of 18:3n-3 was onl y 1.6% in eggs of captive pheasants compared with 27.9% in eggs of the wild birds. The proportions of 18:3n-3 in yolk TAG of housed, free-range and fe ral geese were 0.6, 6.6 and 19.3% respectively. It is suggested that these differences arise from the predominance of linoleic acid (18:2n-6) as the m ajor polyunsaturate in the commercial grain-based feeds whereas geese and p heasants in the wild consume grasses and green shoots in which 18:3n-3 is t he main fatty acid. The concentrations of vitamin E and carotenoids in the yolks of the free-range and feral geese were much greater than in those of the housed geese. Thus the developing embryos of pheasants and geese in the wild will have access to far higher levels of n-3 polyunsaturates and lipi d-soluble antioxidants compared with embryos of the housed birds. (C) 1999 Elsevier Science Inc. All rights reserved.