Abstract
The effects of supplementing the rations of laying hens (Dekalb XL-L) with linseed oil on the lipid composition of egg yolk were investigated. The hens were fed rations containing five different levels (0%, 1%, 2%, 4% and 5.9%) of linseed oil for more than 35 days. Variations in the level of linseed oil had no effect on the contents of total lipid, neutral lipid and polar ligid in egg yolk. However, analysis of the fatty acid composition of the total egg yolk lipid showed that, with increasing levels of dietary linseed oil, the contents of α-linolenic acid (18: 3, ω3) and eicosapentaenoic acid (20: 5, ω3) increased, while the contents of oleic acid and arachidonic acid (20: 4, ω6) decreased. The egg yolk from the 1% linseed oil group contained a higher concentration of docosahexaenoic acid (22: 6, ω3) and a lower concentration of linoleic acid (18: 2, ω6) in comparison with the 0% linseed oil group; a further increase in the level of dietary linseed oil gave the same values as those in the 1% group. Consequently, the ratios of ω3 and ω6 fatty acids in the total egg yolk lipid in the 0%, 1%, 2%, 4% and 5.9% linseed oil groups were 0.11, 0.31, 0.44, 0.69 and 0.92, respectively. The concentrations of α-tocopherol in egg yolk from the 0% and 1% linseed oil groups were similar, but linseed oil suppiementation at levels of more than 2% significantly reduced the α-tocopherol contents. The ω3/ω6 ratio of fatty acids in the feed containing 1% linseed oil was 0.43.
