| Omega-3 enriched eggs In the case of fats and fatty acids, this digestion and breakdown process is not as complete. Some fatty acids are absorbed intact and transferred to the egg yolk. Thus if dietary changes are made, some corresponding changes in yolk composition may occur. This knowledge has been used to modify the egg yolk fats to include more omega-3 fatty acids to meet consumer needs. It is believed that many consumers eat less than the optimal amount of omega-3 atty acids for their health, and thus omega-3 enriched eggs can make up some of this deficiency. The dietary changes usually involve replacing some of the fat and protein supplied from soybean meal with other ingredients. Flax seed is the most common, but this supplies mainly the short chain linolenic acid (LNA). The hen converts some of the LNA to the more desirable long-chain omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). However, quantities of these can be increased to a greater extent by feeding them directly in the form of fish meals or fish oils. The amount of these ingredients that can be incorporated into the diets of laying hens is limited by the fact that at high levels, undesirable flavours may be introduced into the egg yolk. Another possibility is to utilize processed algae as a nutritional supplement; it is the original source of the omega-3 fatty acids found in fish oils. The omega-3 enriched egg was the first such product to be commercially successful. The original product was produced in Alberta, Canada in 1990 and was marketed as “Dr. Sim's Designer Egg”. Since then, a very wide range of similar products has been successfully marketed around the world. The Columbus Egg, sold and franchised by BELOVO in Belgium, takes the concept one stage further, claiming that its unique combination of omega-3 and omega-6 fatty acids mimics the ratio found in the diet of our hunter-gatherer ancestors some 4 million years ago. Lutein enriched eggs Lutien is considered to be an important nutrient in the human diet, as it may help to prevent age-related macular degeneration (AMD) and partial or complete blindness associated with this condition. Research at the University of Guelph has shown that increasing the amount of lutein in the diet of laying hens led to an increase in lutein in egg yolks. Lutein is supplied as a synthetic supplement, and efficiency of transfer to the yolk, while somewhat limited, may be enhanced by inclusion of dietary ingredients such as corn gluten meal and/or alfalfa. However, even with the latter feed ingredients, the researchers were unable to increase egg yolk lutein content above about 1.7mg/60 g of egg contents. This is 5-8 times the level found in eggs from normally fed layers. However, the estimated daily requirement of humans for lutein is about 8 mg/day. Research continues in an effort to further increase the level of lutein in enriched egg yolks. Folic Acid or Folate enriched eggs There is general agreement among nutritionists that the human diet is marginal or deficient in folic acid. Folate in the blood stream reduces birth defects and also influences the level of homocysteine in the blood, a factor in prevention of heart disease. Scientists at the University of Manitoba studied the incorporation of dietary folic acid into eggs, where it appears as 5-methyltetrahydrofolate. Levels of up to 50μg per egg were achieved, and this represents approximately 25% of the supposed human daily requirement. Eggs from hens on unsupplemented diets contain about 17μg of folate. Selenium enriched eggs Selenium is not uniformly distributed in the world's soils, and thus not in crops produced from them, nor in the animals fed those crops. Early research on selenium in nutrition concentrated on toxicity: in some states in the US (e.g. South Dakota) animals were poisoned when they ate certain plants. However, later research demonstrated that selenium is an essential element, although the requirement and toxicity levels are not far apart. Recommended daily intakes vary in different countries but range from 55mg/day in the US to 75mg/day for men (60mg for women) in the UK. It has been stated that the average daily intake of selenium in the UK in 1990 was only 30mg/person. Feeding organic selenium to layers can increase egg selenium 7-fold when compared with unsupplemented hens. This knowledge has been commercially applied and as of 2008, according to Surai (in Proceedings of the Symposium, Return of the Good Egg) almost 50 brands of selenium enriched eggs were available in 24 countries. Egg selenium may also be increased by feeding inorganic selenium, but the process is not as efficient as when organic sources are used. Other Egg Enhancements A variety of other possible enhancements to eggs have been studied, but not necessarily applied commercially. CLA Conjugated linoleic acid is the name given to a mixture of isomers of linoleic acid that occur in the fats of ruminant animals and in dairy products. Their health effects were originally thought to be as anti-carcinogens, but subsequently, they have also been associated with lipid metabolism and with the immune system. As nutritional advice tended to reduce consumption of red meat and dairy products in order to avoid saturated fats, so consumption of CLA also tended to decrease. CLA occurs naturally in eggs, but at very low levels. The level of CLA in eggs can be raised by feeding it in the hens' diets, to the point at which one egg might provide 15-40% of the presumed daily requirement of the human. So far, (early 2009) this has not been practiced commercially. Isoflavones Isoflavones are chemicals that occur naturally in soybeans and in foods made from them (e.g. tofu, soy milk, etc.) They are chemically similar to oestrogen. They are thought to have health benefits in terms of relief of menopause symptoms, and also by reducing risk of some cancers. Some preliminary research has been conducted to incorporate them into eggs, but no commercially applicable data are available. Vitamins Many of the Vitamins are naturally present in eggs in significant amounts (see the section on Egg Composition). Attempts to increase Vitamin levels in eggs have met with mixed results because the hen naturally deposits only the amount necessary to support embryonic growth and development. Levels of the following Vitamins and micro-nutrients have been successfully increased by raising the levels in the hens' diets: Vitamin A, Vitamin D3, Vitamin E, Vitamin B12 folic acid, riboflavin, biotin and pantothenic acid. However, the rate at which these nutrients are incorporated into eggs varies enormously. In many cases, the cost of increasing the Vitamin level cannot be recovered by an acceptable increase in the price of the eggs. Antibodies While not strictly in the category of nutrients, antibodies are extremely important components of eggs. They occur in the yolk and are called yolk immunoglobulins or IgY's. Antibodies are naturally deposited into eggs by the hen to provide protection for the newly hatched chick against pathogens. In natural conditions, antibodies will be deposited to protect against pathogens that the hen has herself encountered. However, it has been found that hens may be artificially induced to raise antibodies against many "foreign" antigens, and deposit them into egg yolks in relatively large quantities. These can be antibodies against human diseases. Subsequently, the antibodies may be extracted from the yolk, or the yolks or eggs used directly by humans to provide passive immunity or even to treat an existing disease condition. The antibodies may also be used in a variety of diagnostic tests. Among the antibodies that have been produced from eggs are: • E. coli • Bovine Serum Albumin • Human Serum Albumin • Salmonella (various serotypes) • Proteoglycan • α-subunit of insulin receptor • lipopolysaccharide • Bovine rotavirus • Human rotatirus • Yersinia ruckeri • Staphylococcus aureus • Streptococcus agalactiae (and other serotypes) • Pseudomonas aeruginosa • Helicobacter pylori • Infectious prion proteins
This list is by no means complete. It is likely that hens will deposit into the egg yolk, antibodies to almost any antigen to which they are exposed. A variety of methods has been developed for extracting and/or purifying the IgY's for use in medical diagnostics, disease treatment or prevention .
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