The effects of different dietary lipids on the fatty acid profiles of eggs produced by 20 and 54 wk old Dekalb laying hens were investigated. Laying hens were subjected to three defined treatments according to the source of lipid added to their diets: soybean oil, beef tallow, and a control diet (without the addition of oil). The experimental design was in a 3x2 factorial arrangement (three treatments and two different ages). The fatty acid composition of the yolks in the eggs produced by the laying hens was analyzed. The eggs produced by laying hens on the soybean oil diet had a large amount of polyunsaturated fatty acids (PUFA) omega-6 (n-6) and omega-3 (n-3) in their yolks (23.55, 2.30% respectively), whereas egg yolks from hens who were given beef tallow had higher percentages of monounsaturated fatty acids (47.53%) compared to soybean oil (47.53%) and the control diet (38.72%). The percentages of trans fats present in the egg yolks in all treatments were considered very low (0.91; 0,11; 0.05%). Young layers are more efficient at depositing n-3 fatty acids (1.40%), specially C22:6 (0.76%) with the best ratio n6:n-3 (13.97) compared to old layers (1.35; 0.72; 14.81% respectively). Based on these results, it was concluded that the amount of fatty acids present in the egg yolks can be modified by the sources of lipids included in the diet and that independent of the sources of lipid in the diet and the age of the chicken, egg yolks have insignificant amounts of trans fatty acids.
Egg yolks; laying hens; beef tallow; soybean oil; fatty acids
