DHA enriched eggs using microalgae in layer diets

C. Chadha, A. Naylor and A. Tsappis


Functional foods have become a hot topic in the food industry due to the push for healthier food products on supermarket shelves. According to the Academy of Nutrition and Dietetics, a functional food is defined as “A food that provides additional health benefits that may reduce disease risk and/or promote good health.”

Enriched eggs offer a way to increase the levels of health promoting micronutrients, without significantly changing eating habits. Consumers buy, cook and eat eggs in the same way, just simply having to choose an enriched brand.

DHA is an essential omega-3 fatty acid
Omega-3 PUFA (polyunsaturated fatty acids) are commonly known for their health benefits to the consumer. This family of essential fatty acids provides a host of health benefits. There are three types of fatty acids in the omega-3 family: alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
Each of these omega-3 fatty acids is considered essential; however, not all omega-3 fatty acids are created equal. DHA is the most important of these fatty acids and is primarily responsible for the benefits commonly associated with omega-3 foods and supplements. Alpha-linoleic acid (ALA) is a short-chain omega-3 that serves as a source of energy and as a building block for EPA and DHA. ALA is commonly derived from linseed and flaxseed in livestock diets and thus is often promoted as an omega-3 in foods largely due to low cost and the abundant availability. Whilst this serves as an energy source, its relative inability to be converted in the body to DHA means that its health benefits are minimal. EPA is a long-chain omega-3 fatty acid important for overall health. Humans do have limited ability to convert dietary ALA to EPA and crucial DHA, however the efficiency of the conversion is very low – less than one percent – and dietary intake of EPA and especially DHA is necessary to maintain sufficient amounts in the body.
DHA is an essential omega-3 fatty acid, most commonly found in wild fish like salmon and mackerel, which feed on marine algae. The active forms of essential omega (n)-3 fatty acids, particularly DHA, in human diets play important roles during pregnancy and early infant development. In adults, high levels of dietary DHA and EPA have been associated with lower rates of coronary heart disease, arrhythmias, atherosclerosis, inflammation, diabetes, and cancers such as breast, prostate, and colon. However, the typical Australian dietary DHA intake falls short of recommendations of 500 mg/day (National Heart Foundation, 2008). Fish oil is the most commonly known supplement for long chain omega-3 PUFA but it is unsustainable as a result of overfishing which is causing depletion in fish stocks in the sea thus there is an ever increasing need in the animal production sector to find new feed resources. These need to be environmentally friendly and use natural resources efficiently. Consumer safety has also been highlighted in the media when levels of polychlorinated biphenyls (PCB’s), which have been linked to cancer, have been found in some supplements.

Algae as a source of PUFA
Algae are gaining attention for their application in the feed and food industries as a highly sustainable source of protein and DHA omega-3. Moreover, the omega-3 content in fish originates from their consuming either the algae directly or other creatures that feed on algae. Algae are a diverse group of simple organisms, ranging from unicellular to multicellular forms such as giant kelp.
The use of algae as a source of PUFA is increasingly globally recognized and further research holds great potential for benefits in human pharmacology and nutrition. Microalgae refer to the numerous microscopic algae that grow in marine or freshwater environments, converting water and carbon dioxide to biomass and oxygen in the presence of sunlight.
Most commercial production of microalgae is done self-trophically in open outdoor circulating raceways or ponds. Under autotrophic growing conditions, microalgae use light energy to fix carbon dioxide, their carbon source, into hydrocarbons with oxygen discharged as waste product. However, open systems are subject to several disadvantages such as airborne contamination and downstream processing. The growth of zooplankton and other species are also drawbacks of an open system. The other commercial production method in growing algae is the heterotrophic system. Heterotrophic species get their energy from organic carbon compounds. By eliminating light from the production process, any fermenter, such as those used for production of medicines, beverages and food additives can be used for heterotrophic algal growth. The heterotrophic method maintains a closed controlled system that provides a more consistent, traceable and pure algal product. By manipulating the physical and chemical properties of the cultural medium, several species of microalgae can produce and accumulate higher levels of specific fatty acids. Specific strains of hetero-trophically grown microalgae thus contain large quantities of high quality eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

Production of DHA omega-3 eggs
A number of global studies have examined the improvements to the egg fatty acid composition from feeding layer hens a diet containing Schizochytrium microalgae (All-G-Rich™, Alltech Inc). These studies were carried out to demonstrate the value of improving the DHA-content in the eggs to the animal, farmer, retailer, consumer and environment. Adding a DHA source into animal diets can naturally increase the DHA levels in food products, providing consumers a way to increase daily intake of DHA to support general health and wellness.
Dietary supplementation with All-G Rich™ can affect the DHA omega-3 content of the whole egg, allowing for an egg with almost 2.5 times the DHA content of a conventional egg. Two research studies were conducted at the University of Kentucky. Study one used 288 Hy-Line week 36 layers with 12 replicates and six birds per unit. Eggs were sampled after four weeks and performance was monitored for 16 weeks. The treatment included a corn-soy based commercial diet with 0, 0.5, 1.0, or 2.0% All-G-Rich™. DHA content measured in study one linearly increased with dietary supplementation of All-G-Rich™. In study two, the trial was performed using 120 Hy-Line week-36 Layers with six replicates and five birds per unit. Eggs were sampled at four weeks. Treatments included a corn-soy commercial diet plus 0, 1.0, 2.0 or 3.0% of ALL-G-Rich™. Performance of the layers as measured in study two was unaffected by treatment.
Changes to the fatty acid composition of the DHA enriched eggs did not affect the sensory and storage qualities of the eggs. The eggs looked, cooked and tasted the same as conventional eggs and flavour was significantly preferred in sensory evaluations. There was no reduction in the efficiency of the egg production of DHA enriched eggs when compared to conventional eggs. The DHA enriched eggs can be promoted as a dietary alternative source to fish. The ability to enrich eggs with DHA provides the egg industry with a unique opportunity to produce an innovative, quality and value-added premium product. The Korean concept of YaShikDongWon correlates food and medicine to the same origin. This notion has never been more important and highlights the importance of functional foods for preventative and therapeutic purposes relating to health. Concepts of health and wellbeing across the world are accelerating from global convergence from increased import and export of ingredients. Functional foods have been a part to this and advancements in modern food backed by scientific evidence have gained public approval.

Consumer demand for superior health quality food products has increased interest in enriching the eggs with DHA omega-3 polyunsaturated fatty acids. This has proven to be a viable method of adding value to eggs for the health-conscious consumers. Algae are gaining attention for their application in the feed and food industries as a highly sustainable source of protein and DHA omega-3.

References are available on request
From the Proceedings of the Australian Poultry Science Symposium