Designer eggs: Altering mother nature's most perfect food
Modifying egg quality can be accomplished by inducing metabolic changes in the hen that can result in synthesis of compounds that essentially end up in her egg.
Another way is to change the characteristics of membrane transport to facilitate movement of compounds into the egg. One of the more common acceptable ways to modify egg quality is to manipulate the diet of the hen such that the desired compounds eventually find their way into the egg. If a food, such as the egg, is nutritionally modified it is referred to as a designer or functional food (American Dietetic Association, 1995).
Nabor (1979) reviewed the transfer of nutrients into the egg. Pigments are not considered nutrients and this is probably why he did not include them in his review. The type of pigment and its concentration are directly influenced by the dietary concentration of any particular pigment. Numerous natural and synthetic pigment sources have been used successfully to pigment eggs. The high protein blue-green alga Spirulina platensis has also been shown to be an efficient pigment source for poultry and eggs (Ross and Dorminy, 1990; Anderson et al., 1991). Newman (1997) reviewed the nutritional benefits of supplementing various species of Spirulina to the animal's diet.
Nabor's classification of nutrients found in the egg and their responsiveness to dietary influence has remained unchanged (Table 1). Since his review more has been learned about how dietary changes influence the egg's nutrient content. Scientific research costing hundreds of millions of dollars has been conducted throughout the world on nutrition and how it influences human health. Since eggs are a rich source of dietary cholesterol, the egg has been the subject of a considerable amount of this nutritional research because of the known relationship between cholesterol and atherosclerosis.
Poultry researchers have been dedicating a considerable amount of their efforts in recent decades to studies with hens in an attempt to lower egg yolk cholesterol to satisfy concerns of health-conscious consumers (Van Elswyk, 1997). Research has shown that not only cholesterol, but the egg content of several other nutrients can be manipulated to produce today's so-called 'designer' eggs. These eggs are marketed as specialty eggs of added value because of their unique features and usually command a higher price than conventional eggs in the marketplace.
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Article made possible through the contribution of Alltech Inc.