The ingredients of animal feed formulation, especially the fatty sources, play a significant role in the production of high-quality food of animal origin. Industrial fat by-products are a major source of feeding fats in Europe. The main objectives of the project were firstly to assess feed fats and oils for their composition and content of sterols (cholesterol and phytosterols) and oxysterols, and secondly to assess the levels of cholesterol and oxycholesterols of chicken and rabbit tissues after feeding with especially formulated feeds containing trans fatty acids and oxidized lipids. The lack of standardized analytical procedure prompted the evaluation of an in-house purification method by comparing it with a number of commonly used methods for the analysis of oxysterols. The saponification and transesterification steps showed rather comparable results. A two-dimensional capillary GC column with different stationary phases (a 35% phenyl column coupled to an apolar 5% phenyl column) was used for better resolution of a large number of oxysterols. This new system improved the separation efficiency and reduced the analytical time for a wide range of oxysterols. The satisfactory purification method and the reliable separation of oxysterols facilitated the qualitative and quantitative assessment of sterols and oxysterols in samples of by-products from chemical and physical refining. A large variation in the levels of sterols and oxysterols was observed in the fat by-products from chemical and physical refining processes for edible fats and oils. The observed variations in the contents and composition of sterols and oxysterols were mainly due to the origins, production facility and different processing conditions of the by-product samples. The highly oxidized lipid and trans fatty acid feeds significantly increased the contents of cholesterol and oxycholesterols in edible parts, e.g. the muscles and livers of chickens and rabbits (0.01< p ≤0.05). Hence, the consumption of products from animals fed with higher levels of trans fatty acids and oxidized lipid feeds may contribute to higher ingestion of cholesterol and oxycholesterols by humans
