Effect Of Dietary PUFA On Lipid Metabolism And Fatty Acid Compositions Of Yolk Lipid Classes In Layers

The two experiments were conducted to evaluate the effect of dietary n-3 polyunsaturated fatty acids and n-6 polyunsaturated fatty acids on performance, lipid metabolism and fatty acid compositions of yolk lipid classes in layers. The aim of present study was provided evidence of theory and practice for producing eggs enriched n-3 polyunsaturated fatty acids. Experiment 1 Effect of dietary PUFA on performance, lipid metabolism and fatty acid compositions of yolk lipid in the layers. One hundred and eighty 26-wk-old Hyline W-36 Brown layers were randomly allotted into four dietary treatments with 5 replications of 9 birds to investigate the effect of dietary added PUFA on performance, lipid metabolism and fatty acid compositions of yolk lipid in the layers. The diet treatments were: The very high n-3 PUFA treatment was wheat-soybean basal diet plus 25% flaxseed, 1% flaxseed oil and 1% fish oil. The high n-3 PUFA one was wheat-soybean basal diet contained 20% flaxseed and 0.5% fish oil. The very high n-6 PUFA one was corn-soybean basal diet plus 20% sunflower seed and 1% sunflower seed oil. Control treatment was corn-soybean basal diet. The laying rate was decreased significantly(P<.05) in the very high n-3 PUFA group, daily feed intake improved in two n-3 group caused feed efficiency decrease greatly(P<.05). As compared with two n-3 PUFA group and control group, the death rate of the very high n-6 PUFA group is high and reached 16.3%(P<.01). The layers given dietaries with PUFA had a lower serum and liver triglyceride than that of control group(P<.05). The layers had decreased yolk triglyceride and cholesterol levels (P<.05) at the very high n-3PUFA diet compared with the very high n-6 PUFA one. The level of yolk lipid oxidation (Malondialdehyde value) in three PUFA groups was significantly higher than that of control group (P<.05). With the increasing of dietary n-3PUFA significantly increased yolk n-3PUFA and decreased yolk n-6PUFA (P<. 05), the ratio of n-6PUFA and n-3PUFA was decreased 1.43:1, and the yolk total n-3PUFA in the very high n-3PUFA group was 585mg compared with 55 and 67mg for eggs from hens fed diet with the very high n-6PUFA and control one, respectively. The present study demonstrated that dietary contained flax seed or sunflower seed increased yolk PUFA significantly but should consider the performance of layers, and n-3PUFA had some different mechanics interfering with lipid metabolism compared with n-6PUFA. Experiment 2 Effect of different PUFA on performance, fatty acid compositions of yolk lipid classes in the layers. Two hundred 46-wk-old Hyline W-36 Brown layers were randomly allocated to five dietary treatments with 4 replications of 10 birds to evaluate the effect of different basal diet, PUFA variety and level on performance, fatty acid compositions of yolk lipid classes in layers. The diets were: each treatment added 25% ground flaxseed, treatment A, B, C and D were wheat-soybean basal diet contained 1%, 2%, 1%, 2% of flaxseed oil, 1%,1%,2%,2% of fish oil and 2%, 0.9%, 1%, 0% of tallow respectively. Treatment E was corn-soybean basal diet added oils same as treatment D. The performance of treatment E (corn-soybean basal diet) is better than other treatments such as laying rate, feed intake and feed/egg ration. The level of yolk lipid oxidation(MDA value) in each treatment added VE and tea polyphenol was still higher than common egg yolk but significantly decreased compared with experiment 1(P<.05). The ratio of n-6PUFA and n-3PUFA was blow 1:1 and the total n-3PUFA was increased 700mg in each yolk of five treatments. The saturated fatty acids of yolk were significantly increased due to added tallow, fed flaxseed oil increased LNA (linolenic acid) and the enrichment of EPA(eicosapentaenoic acid) and DHA(docosahexaenoic acid) was resulted from added fish oil. The yolk fatty acids composition of PC (Phosphatidylcholine), PE (Phosphatidylethanolamine) and TG (Triglycerides) also showed this trend. The enrichment of LNA in eggs was mainly in TG. And the longer chain n-3 fatty acids such as EPA, DPA, DHA, were deposited exclusively in PC and PE, particularly in PE. It was feasible produced eggs that enriched n-3PUFA 700mg per yolk and the ratio of n-6PUFA to n-3PUFA was blow 1:1 through dietary regulation.