Fatty acids of glycerolipids and glycerophospholipids, carotenoids and α-tocopherol in egg yolk throughout the laying period of hens reared in a certified free-range production system

The study investigated the yolk composition of eggs laid during the entire productive period of Hy-Line Brown hens reared under a free-range production system certified by Humane Farm Animal Care (HFAC). The fatty acids of glycerolipids and glycerophospholipids, carotenoids (lutein, zeaxanthin, astaxanthin, canthaxanthin, β-carotene), α-tocopherol and oxidative stability, were determined in both fresh and stored eggs (28 days at +4°C) coming from laying hens at 28, 62 and 84 weeks of age housed in three experimental henhouses with access to pasture complemented with alfalfa-pack silage. Within the results, the most relevant finding was that the saturated fatty acids are lower at 62 and 84 weeks of age compared to 28 weeks. Palmitic acid, an atherogenic fatty acid, followed a similar pattern. Conversely, the monounsaturated fatty acids, mainly oleic acid, showed a rise at 62 and 84 weeks compared to 28 weeks. The polyunsaturated fatty acids showed a progressive slight decrease of their level from 28 to 84 weeks. That decrease was observed for linoleic acid, α-linolenic acid, arachidonic acid, and DHA, while EPA showed an inverted pattern. Lutein, zeaxanthin and particularly α-tocopherol were present at nutritionally relevant levels in the yolk at the three ages of hens. The oxidative status of eggs was higher after storage at 28 but not at 62 and 84 weeks of age. The cold conservation of eggs did not substantially affect the composition of fatty acids nor of carotenoids and α-tocopherol. Overall, the findings show an interesting nutritional value of the yolks produced in a free-range system in spite of the fact that some decrease related to the age of hens or storing were observed. Taking into account the intake recommendations for consumers, the consumption of two eggs, as a basis, ensures a noticeable part of the intake recommendations of fatty acids such as EPA and DHA, as well as lutein, zeaxanthin, and α-tocopherol.