Seventy- two 26-weakk-old white leghorn layers (w-36) were fed commercial diets containing 0, 2 and 4 fish oil and the diets were iso-caloric and iso-nitrogenous. Hens were randomly assigned to 3 treatment diets, with 3 replicates and 8 layers in each. The experiment was conducted over a period of 12 weeks in order to study the effects of feeding fish oil on fatty acid composition of egg yolks. The yolk of eggs was extracted and cholesterol content was determined in each period. Statistical analysis of results was performed using the general linear procedure (GLM) of the SAS and means were compared using Duncan’s multiple range test. As a result, saturated fatty acid (myristic, palemitic and stearic acid), ω-7 (palemitoleat) and ω -9 (oleat) and arashidonat in egg yolk was not significantly (P>0.05) different among treatments, but the linoleat and ω -6 fatty acid were decreased in all FO treatments (P<0.05). The linolenic acid did not vary in treatments but the other ω -3 fatty acids (eicosapentaenoate and docosahexaenoate) were increased in FO treatments and there was a statistically significant difference between treatments (P<0.05). The ω -6/ ω -3 ratio was decreased from 18 in control to 3.8 and 2.31 at 2 and 4% treatments, respectively(P<0.05).

Keywords: Kilka Fish oil, Layer hen, Egg yolks, Omega-3 fatty acid.

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