Udk 619:636.5.084.524 Egg Yolk Lipid Modifications by Fat Supplemented Diets of Laying Hens

The aim of this study was to investigate the possibility to modificate the total lipid and cholesterol level, as well as fatty acid composition of egg yolks, by supplementing diets of laying hens with different fats. The trial was conducted in two six week experiments. Experiment I was conducted on 180 Isa Brown hens assigned to two age categories: 36 months old (O), and 27 weeks of age young (Y) hens. Both age categories were divided into three groups: control groups fed a diet I with no supplemented fat (OC and YC); experimental groups fed a diet II supplemented with 3.2% of palm oil (OP and YP) and experimental groups fed a diet III supplemented with 2.5% of lard (OL and YL). In Experiment II 45 Lohman Brown hens of 56 weeks of age were randomly assigned into three groups of 15 birds each and were fed with three experimental diets supplemented with either 3% fish oil (group FO), 3% palm olein (group PO) or with 3% lard (group L). The results of our trial support the thesis of constant cholesterol content in egg yolk, that was accepted by the majority of researchers, although it was possible to affect the levels only in some conditions, as for example by the age of hens in Experiment I, or by feeding Lohman Brown hens with 3% of supplemented lard in Experiment II. However, the experiment proved the possibility of altering egg yolk fatty acid composition, this being a trend in actual investigations of egg yolk cholesterogenic modification.