Enriching Eggs of Laying Hens with Multiple Bioactive Nutrients for Improving Human Health

141 pagesThe USA faces an epidemic of obesity and other non-communicable disorders. Major causes of death including cardiovascular disease (CVD) and diabetes are correlated with poor nutrition and dietary habits, which can be modulated through improving the nutritional quality of largely consumed foods such as eggs. Animal products, particularly eggs, have a lot of potential for improvement in terms of nutritional composition. Previous studies by our group have demonstrated that laying hens are capable of enriching into their eggs health promoting compounds including a potent antioxidant astaxanthin (AST), the long chain omega-3 fatty acid docosahexaenoic acid (DHA), and the pre-activated form of vitamin D3 calcifediol. When these compounds are transported into yolks, their molecular forms are changed to be incorporated into phospholipids in the case of DHA, bound to proteins, or hydroxylated such as calcitriol. In order to evaluate how the metabolism of the laying hens changes the bioavailability and potency of these three compounds, murine models were used to simulate dietary consumption of these eggs by humans. Overall, the objectives of this thesis research were: to determine if it’s possible to produce eggs which contain AST, DHA, and calcifediol at concentrations which can meet a person’s daily requirement, understand how these compounds influence the metabolism and endogenous pathways of laying hens to further manipulate them, produce a practical combination of these compounds for producers, and evaluate the health promoting effects of these eggs for human consumption. The first series of experiments were to produce eggs enriched with the aforementioned health promoting agents which involved three laying hen trials: 1) Enrich the eggs and tissues of hens with AST from the microalgae Haematococcus pluvialis (Heliae Development, Arizona), 2) Enrich eggs and tissues with microalgal DHA from Aurantiochytrium (Heliae Development, Arizona), and 3) Enrich eggs and tissues with calcifediol from the vitamin D supplement Rovimix (DSM Industries, Netherlands) alongside both DHA and AST from the previous two studies. All three studies had similar experimental designs with 10 hens per treatment groups and incremental or combined dietary doses of the testing ingredients for 6 weeks after which hens were euthanized and blood and tissues were collected. Major findings included an accumulation of AST in the eggs of tissues which improved overall oxidative status of hens and eggs, an enrichment of DHA in eggs and tissues but with a sharp decrease in enrichment efficiency past 2% of the microalgae and a suppression of overall lipid metabolism. Calcifediol was capable of being enriched at levels up to 9 ug/100 g of yolk when included in the diets of hens at 200 ug/kg of diet. When added in combination, DHA, calcifediol, and AST did not impair each other’s enrichment. The second phase of experiments involved feeding the enriched egg yolks from the first three layer studies to mice to evaluate if these yolks could improve their health. Two feeding trials were conducted with the first involving either DHA or AST enriched egg yolks, and the second involving DHA, AST, and calcifediol enriched egg yolks. Mice were fed yeast-sucrose mash diets which were supplemented with freeze-dried egg yolk products enriched with DHA, AST, and(or) calcifediol. Studies were either 6 or 8 weeks long. At the end, mice were euthanized and tissues collected. Parameters of lipid metabolism and general health were measured in various tissues including the liver, adipose, gastrocnemius muscle, and cardiac muscle. Major findings included a very sharp decrease in heart triglyceride content by yolk enriched with AST. The yolk enriched with DHA down-regulated lipid anabolism and storage in the tissues at both the biochemical and molecular levels