Ageing corn results in the pale-coloured egg yolks with decreased polyunsaturated fatty acids

An experiment was conducted to study the effects of ageing corn (AC, stored for 4 years) and the supplementation of soybean oil on the egg quality, egg yolk cholesterol and fatty acid profile, serum parameters and performance of laying hens. Four treatments were used under a 2 x 2 factorial arrangement with two types of corn (regular corn stored for 6 months, and AC), and supplementation with or without soybean oil (2 g/kg) in the diets. Lohmann commercial laying hens were fed the trial diets as corn-soybean meal-based diets for 8 weeks from 51 to 58 weeks of age. Egg production, egg weight, feed conversion ratio and egg quality were not affected by dietary treatment. Dietary AC increased the serum total bile acids content (P < 0.01) of laying hens, and the monounsaturated fatty acids (MUFA, P < 0.01) of egg yolks, while it decreased the serum total cholesterol (TC, P < 0.05) of laying hens, and the egg yolk colour, polyunsaturated fatty acids (PUFA, P < 0.01) and n-6 PUFA contents. Soybean oil supplementation significantly increased the serum TC (P < 0.05) and total triglycerides (P < 0.05) of laying hens, and the n-6 PUFA (P < 0.01), n-3 PUFA (P < 0.01) and unsaturated fatty acids (P < 0.01) of egg yolks, while it decreased the average daily feed intake (P < 0.01) and serum very-low-density lipoprotein cholesterol (P < 0.05) of laying hens, and the saturated fatty acids (P < 0.01) and MUFA (P < 0.01) of egg yolks. In conclusion, the AC in laying hen diets did not significantly affect hen performance but resulted in pale-coloured egg yolk and decreased the PUFA and n-6 PUFA in egg yolk.