| Two experiments were undertaken with attempt to produce the eggs rich in n-3 polyunsaturated fatty acids but having low level of cholesterol (CHO) content. Experiment I was conducted to evaluate the effects of linseed oil and Cu supplementation into diets for layers on the egg yolk polyunsaturated fatty acids (PUFA) profiles and the contents of CHO. Experiment II was conducted to study the effects of dietary different oil sources on the performance and content of PUFA in egg yolk.One hundreds and sixty-two 50-week-old healthy layers ( Hy-line ) were used in experiment I. The layers were assigned randomly to 9 groups of 18 layers each. A completely randomized design was used in a 3 x 3 factorial arrangement of treatments with 3 linseed oil level: 0%, 2% and 4%; and 3 Cu levels: Oppm, 125ppm and 250ppm. The results showed as follow:l)Dietary linseed oil and Cu significantly (P<0.05) influenced the egg production and feed-egg ratio. The laying rate increased but the feed-egg ratio decreased with the increasing of dietary linseed oil. Compared with the control (0% linseed oil and 0 ppm Cu), the diet containing 4% linseed oil significantly (P<0.05) increased the laying rate by 12.2%. The laying rate of birds fed diets without linseed oil numerically decreased with the increasing of Cu supplementing level. However, the detrimental effect of high level of Cu supplementation on the laying rate could be reduced significantly (PO.05) by the use of linseed oil in the diet.2)Dietary Linseed oil significantly (P<0.05) increased the weight of single egg and egg white but had no effect (P>0.05) on the egg shape index, weight of egg shell and egg yolk, Haugh unit and egg shell thickness. The egg quality was also not affected by Cu supplementation (P>0.05).3)The linolenic acid concentration of egg yolk increased significantly (P<0.05) with the increasing of dietary linseed oil. The n-6PUFA/n-3PUFA ratio was significantly decreased (P<0.05) as the dietary level of linseed oil increased. The diets with 2% and4% linseed oil but without Cu supplementation significantly increased the linolenic acid concentration in the yolk by 11 and 16 times, respectively, which indicated that linolenic acid content of egg yolk was strongly correlated with the fatty acid profile of the diet. Increasing of dietary linseed oil level resulted in significantly (P<0.05) increase of eicosapentaenoic (EPA) and docosahexaenoic (DHA) in the egg yolk , which indicated that linseed oil in the diet could be changed into EPA and DHA by layer. The concentration of linolenic acid in egg yolk was not significantly (P>0.05) affected by Cu supplementation.4)Compared with the control, supplementation of 125 ppm and 250 ppm Cu to the diets significantly (P<0.05) decreased CHO content in the egg yolk by 16.5% and 18.2%, respectively. However. CHO in egg yolk was not affected by the dietary linseed oil.5)The serum total CHO. LDL-C, TG concentrations significantly (PO.05) decreased, while HDL-C significantly (P<0.05) increased with the increasing of dietary Cu level. However, all these parameters in serum were not affect by the linseed oil.Ninety 50-week-old healthy layers( Hy-line ) were used in experiment II. The layers were randomly assigned into 5 groups of 6 replicates each. Each replicate contained 3 layers. The layers were subjected to diets with 2% palm oil (control), 2% linseed oil, 4% linseed oil, 4% fish oil. and 4% Huoma oil. The results indicated as follow:1 )The highest laying rate was observed in layers fed diet with 4% linseed oil. The laying rate of birds fed diet with 4% linseed oil was higher than that of layers fed control diet by 12.28%. No significant differences on laying rate was observed among birds fed diets with 4% fish oil. 2% linseed oil or 2% palm oil. However, compared with the control diet, inclusion of 4% Huoma of diet significantly deceased laying rate by 19.29 %.2)Different oils sources had not significant (P>0.05) effect on the serum total CHO, LDL-C, HDL-C and TG concentrations, but oil from linseed, fish...
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