Incorporation of different polyunsaturated fatty acids into eggs

An experiment was carried out to examine thoroughly the relationships among different n-3 and n-6 polyunsaturated fatty acids (PUFA) in the diet, thei r deposition into the eggs' fat, and their effect on hens' laying performan ce. A diet enriched with 4% fish oil (FO) was fed to the birds throughout t he 14-wk laying period (Treatment 1; T1); this was the same oil source that was replaced in proportions of 25, 50, 75, or 100% with four different fat sources, resulting in 17 isocaloric dietary treatments: linseed oil (LO; T 2 to T5), rapeseed oil (RO; T6 to T9), sunflower oil (SO; TIO to T13), and tallow (T; T14 to T17). Performance parameters were recorded weekly and ana lyzed on the basis of the replacing fat source. At the end of the 14-wk exp erimental period, eggs were collected, and their fatty acid (FA) profile wa s determined. Performance parameters were not significantly different among grouped treat ments. Smaller proportions of FO in diets resulted in lower values of satur ated and higher values of n-6 FA contents, regardless of the fat source use d when replacing FO. The n-6 content increased mostly because of the rise i n linoleic acid (LA), although the level of arachidonic acid (AA) was alway s higher when FO was completely suppressed. The amount of the different n-3 long-chain PUFA was lower (P < 0.001) when FO was present in lesser propor tions in the diet. However, the slope of the decline of these FA changed ac cording to the included fat. Replacing FO with LO resulted in the lowest de cline of its derivatives by elongation and desaturation and an increase in the total n-3 FA in the form of linolenic acid (LNA).