Welcome to the The Incredible Edible Egg™ Eggcyclopedia, where you can access the latest egg information from A-Z. The Eggcyclopedia was developed by the American Egg Board (AEB) on behalf of America's egg farmers who are committed to caring for their hens and producing high-quality eggs for you and your families.

Just click on any letter below to bring up a list of egg terms and their related definitions.


Egg production during the year ending November 30, 2011 totaled 91.9 billion eggs, up slightly from 2010. Table egg production, at 79.0 billion eggs, was up 1 percent from the previous year.


Maximum production of top-quality eggs starts with a closely controlled breeding program emphasizing favorable genetic factors. The Single-Comb White Leghorn hen dominates today's egg industry. This breed reaches maturity early, utilizes its feed efficiently, has a relatively small body size, adapts well to different climates and produces a relatively large number of white-shelled eggs, the color preferred by most consumers. Brown-shelled eggs are now available in most markets, but have long been the traditional favorite in the New England region. Commercial brown-egg layers are hens derived from the Rhode Island Red, New Hampshire and Plymouth Rock breeds, which predominated in that area of the country.

– See Color, shell

Resistance to Disease

Selective breeding is reinforced by good sanitation and vaccination.


Light control

Of primary importance during both the growing and laying periods, controlled, low-intensity light can be used in house systems to delay sexual maturity until the bird’s body is big enough to produce larger eggs. Intensity and duration of light can be adjusted to regulate production.


Laying houses maintained between 57º and 79ºF (14º and 26ºC) are desirable.


A relative humidity between 40 and 60% is optimal.

Housing Systems

America's egg farmers are committed to producing a fresh, high-quality product and therefore are committed to the health and well-being of their hens. Housing systems today vary, but all ensure the hens are provided with adequate space, nutritious feed, clean water, light and fresh air. America's egg farmers produce eggs from multiple production systems -- conventional, cage-free, free-range, and enriched colony. All organic systems are free-range.

Conventional: Eggs laid by hens living in cages with access to feed, water, and security. The cages serve as nesting space as well as for production efficiency. In this type of hen house, the birds are more readily protected from the elements, from disease and from natural and unnatural predators.

Cage-free: Eggs laid by hens at indoor floor operations, sometimes called-free-roaming. The hens may roam in a building, room or open area, usually in a barn or poultry house, and have unlimited access to fresh food and water, while some may also forage for food if they are allowed outdoors. Cage-free systems vary and include barn-raised and free-range hens, both of which have shelter that helps protect against predators. Both types are produced under common handling and care practices, which provide floor space, nest space and perches. Depending on the farm, these housing systems may or may not have an automated egg collection system.

Free-range: Eggs produced by hens that have access to outdoors in accordance with weather, environmental or state laws. In addition to consuming a diet of grains, these hens may forage for wild plants and insects and are sometimes called pasture-fed hens. They are provided floor space, nesting space and perches.

Organic: Eggs produced according to national U.S. Department of Agriculture organic standards related to methods, practices and substances used in producing and handling crops, livestock and processed agricultural products. Organic eggs are produced by hens fed rations having ingredients that were grown without most conventional pesticides, fungicides, herbicides or commercial fertilizers.

Enriched Colony: A production system that contains adequate environmental enrichments to provide perch space, dust bathing or a scratch area(s), and nest space to allow the layers to exhibit inherent behavior. Enriched colony systems are American Humane Certified.


Since more is known about the nutritional requirements of the chicken than of any other domestic animal, feed rations are scientifically balanced to assure layer health along with optimum quality eggs at least cost. Automatic feeders, activated by a time clock, move feed through troughs that allow for feeding ad libitum. Birds are also provided water at all times via nipple valves separate from the feed troughs.

Poultry rations are designed to contain all the protein, energy (carbohydrates), vitamins, minerals, and other nutrients required for proper growth, egg production, and health of the layer hen. Feed might be based on sorghum, grains, corn, cottonseed meal or soybean meal, depending on the part of the country in which the ration is produced and which ingredient is most available and cost effective. The hen's ration may contain the same types of additives approved for human food. Antioxidants or mold inhibitors (also used in mayonnaise and bread) are added to maintain the quality of the feed. An additive is not approved for use in poultry feed unless adequate research has been undertaken to determine its pharmacological properties and possible toxicity and to discover any potentially harmful effects on animals.

Federal regulations prohibit the feeding of hormones to any kind of poultry in the U.S.

How much a layer eats depends upon the stage of life, the hen's size, the rate of egg production, temperature in the laying house and the energy level of the feed. In general, about 4 pounds of feed are required to produce a dozen eggs. A Leghorn chicken eats about 1/4 pound of feed per day. Layers of brown-shelled eggs are slightly larger and require more feed.

The type of feed affects egg quality. Shell strength, for example, is determined by the presence and amounts of vitamin D, calcium and other minerals in the feed. Too little vitamin A can result in blood spots. Yolk color is influenced by yellow-orange plant pigments in the feed. Maximum egg size requires an adequate amount of protein and essential fatty acids.

Flock Management

Molting, or loss of feathers, is a natural occurrence common to all birds regardless of species. In the wild, egg quality declines as the hen ages and, at about 18 to 20 months of age, molting occurs and egg production ceases. In conventional egg production, a fairly common practice is to place the flock into a controlled molt. A low-protein diet minimizes stress on the birds as they go through this transition period. After a rest period of 4 to 8 weeks, the birds start producing eggs again. Researchers have found that two periods of controlled molting, one at 14 months and another at 22 months, increases egg production more than one molt at 18 or 20 months, though few egg farmers place flocks into two controlled molts. Controlled molting is not permitted in organic flocks, though natural mottling can occur.

Egg Handling

In most commercial egg production facilities, automated belts gather eggs every day. Gathered eggs are moved into refrigerated holding rooms where temperatures are maintained between 40° and 45°F (4° and 7°C).

– See Cleaning

Egg Processing and Distribution

Some producers sell their eggs nest-run (ungraded) to processing firms which clean, grade, size and carton the eggs and ship them off to retail outlets. Most farms and ranches carry out the entire operation.

– See Egg ProductsEgg Products Inspection ActGradingNest-Run Eggs