Differences in egg lipid and antioxidant composition between wild and captive pheasants and geese
1999
Speake, B.K. | Surai, P.F. | Noble, R.C. | Beer, J.V. | Wood, N.A.R.
The aim of this study was to assess the differences in yolk lipid composition of pheasants and geese between birds maintained in captivity on commercial grain-based diets and their counterparts in the wild which are free to select their diets from the environment. The most striking difference was that the proportion of alpha-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 example, in yolk TAG, the level (wt.% of total fatty acids) of 18:3n-3 was only 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 feral 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 major polyunsaturate in the commercial grain-based feeds whereas geese and pheasants in the wild consume grasses and green shoots in which 18:3n-3 is the 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 lipid-soluble antioxidants compared with embryos of the housed birds.
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