The nutritional manipulation of the diets of laying hens to include sources of n–3 fatty acids promotes the deposition of these nutrients into egg yolk. n–3 Fatty acid-rich eggs may provide an exciting alternative food source for enhancing consumer intake of these proposed healthful fatty acids. Care must be taken when designing n–3 fatty acid-rich poultry rations, however, to assure that the resulting egg fatty acid profile is useful for promoting consumer health yet maintaining egg sensory quality. In study 1 laying hens were fed on diets supplemented with graded levels of menhaden oil (MO), rich in both eicosapentaenoic acid (EPA; 20:5n–3) and docosahexaenoic acid (DHA; 22: 6n–3), for 4 weeks to determine maximal yolk fatty acid deposition attainable without sensory compromise. Yolk fatty acids were analysed for an additional 4 weeks, post-MO removal, to investigate yolk n–3 fatty acid tenacity. Dietary MO levels between 15 and 30g/kg yielded the greatest yolk n–3 fatty acid content; however, only eggs from birds fed with 15g MO/kg were considered acceptable by trained flavour panelists. Evaluation of eggs from hens fed with 15g MO/kg during storage verified that the shelf-life of enriched eggs was comparable with that of typical eggs. In study 2, graded levels of whole or ground flaxseed were used for the deposition of linolenic acid (LNA; 18:3n–3) and to determine in vivo production of DHA from dietary LNA for yolk deposition. Flaxseed form influenced yolk n–3 fatty acids only when given at 150 g/kg diet. In vivo production of DHA, while significant, was not enhanced by increasing the level of dietary flaxseed nor by grinding the seed. In the third study, a DHA-rich natural marine alga (MA) was investigated as an n–3 fatty acid supplement. Despite similar DHA profiles, dietary MA was found to be more efficient for yolk DHA deposition than dietary MO. These studies suggest that there are numerous viable n–3 fatty acid supplements for poultry rations. It must be realized, however, that the fatty acid profile of the final product varies substantially depending on which supplement is fed.
The effect of diet composition and length of storing
eggs on changes in the fatty acid profile of egg yolk