Comparison of n-3 fatty acid sources in laying hen rations for improvement of whole egg nutritional quality: a review.Br J Nutr. 1997 Jul; 78 Suppl 1:S61-9.BJ
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 30 g/kg yielded the greatest yolk n-3 fatty acid content; however, only eggs from birds fed with 15 g MO/kg were considered acceptable by trained flavour panelists. Evaluation of eggs from hens fed with 15 g 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.