Abstract This study aimed to investigate the effects of dietary supplementation with modified-hen-egg-yolk on plasma lipids and lipoprotein profiles in rats. During the four-week-experiment, 64 Wistar rats were divided into four groups of 16 (eight of both sexes), and fed commercial rat food (group C); food containing 70% commercial rat mixture and 30% freshly cooked egg yolk originating from laying hen eggs fed with 3% fish oil (group F); 3% palm olein (group P), or 3% lard (group L). The cooked egg yolk in the rat diet affected the concentrations of plasma total and LDL-cholesterol in males of the P and L groups. Cholesterol and total fat in the diet did not have a hypercholesterolemic effect on their own, but when in combination with fatty acid composition, they could contribute to an increase in plasma total and LDL cholesterol concentrations in rats. HDL-cholesterol was the most resilient plasma lipoprotein of rats to dietary treatments in our experiment. Compared to the control group, the addition of hen egg yolk to the rat diet regardless of its quality, adversely affected the values of HDL-C/TC and HDL-C/LDL-C in both males and females.

The aim of this study was to research the impact of a diet supplemented with egg yolks of modified content, having in mind the type of fat added to the laying hens diet, on the brain lipids and their fatty acid composition in rats. During four weeks of the experiment, 64 Wistar rats, divided into four groups of 16 animals each (eight animals of both sexes), were fed the commercial rat feed (group C), or the feed that contained 70% of the commercial rat feed and 30% of freshly boiled yolks from the eggs originating from laying hens fed with 3% fish oil (group F), 3% palm olein (group P) or 3% lard (group L). Concentration and content of total lipids and total cholesterol, as well as the fatty-acid composition of the total brain lipids were determined in the lipid extracts of the rats brains. Under unfavourable conditions, which in our case could be high dietary intake of the total fat due to egg yolk addition, the amount of total fat in the brain tissue or the mass of the organ itself can be changed. Applied dietary treatments could also influence the level of de novo synthesis of total cholesterol in the rat brain. High dietary fat intake, as well as the fat quality regarding its fatty acid composition, appear to be able to significantly influence the fatty acid profile of the total brain lipids in adult rats, whereas the level and quality of the changes also depend on sex.

The aim of this study was to examine the effects of diets supplemented with egg yolks of modified composition on the fatty-acid composition and lipid content in rat’s liver. During four weeks of the experiment 64 Wistar rats were divided into four groups of 16 individuals each (eight individuals of both sexes) and fed a commercial feed mixture for rats (group C) or diet containing 70% commercial mixture for rats and 30% freshly cooked egg yolks from laying hens fed diets with 3% fish oil (group F), 3% palm olein (group P) or 3% lard (group L). Dietary supplementation with egg yolks significantly increased the hepatic cholesterol pool in rats, regardless of the type of fat in the diet of laying hens from which the eggs originated. The content of α-linolenic acid in the liver of male rats in group P was 4-6 times higher compared to males in the other groups. Liver lipids and their fatty-acid composition differ by both, sex and dietary modified egg yolk composition in rats.