Basic Principles
Egg production in the United States has undergone a remarkable transformation. Before the twentieth century, hens ran loose around the farmyard, largely fending for themselves. Around the late 1800’s, farm flocks came into being, and egg production became a serious part of the farm enterprise. Hens were given their own housing and provided with feeders, waterers, roosts, and nests, as well as a fenced-in yard. The farm flock system allowed for applying important management principles, such as proper feeding, breeding, and egg collection. The next advance took place around the 1960’s with the emergence of farms that specialized in egg production. The farmer-manager could then focus entirely on egg production and use the latest in management and feeding techniques and production stock. Later in the twentieth century, egg producers became vertically integrated, with all aspects of production and marketing under the control of the same firm. The farmer-producer became just one part of the entire system.
Egg production involves genetic research to develop strains of highly productive hens; proper management of growing pullets to maximize their potential as laying hens; the use of advanced technology in buildings, equipment, feeding, and lighting for maximal egg production at minimal cost; and the development of new egg products for the consumer. It can also involve support services such as feed mills and transportation. Modern intensive production practices involving millions of birds have come under criticism as factory farming and have raised questions of animal welfare that must be addressed by the producer.
How It Works
Egg production begins with the selection and development of breeding stock. Many breeds of chickens have developed over time, but for commercial purposes, the laying hen (layer) must be highly productive and efficient in converting feed into eggs. These criteria are met by the white leghorn breed, which is light in body weight, is highly active, and produces a white egg. A very few breeding companies dominate the supply of egg production chicks, and they have their own specialized lines or strains of breeders. The white leghorn has been overwhelmingly adopted by the egg industry, but other breeds are used in markets that prefer a brown egg. Traditionally, this has involved using heavy breeds, such as the New Hampshire or Rhode Island red. The development of specialized lines and crossbreeds has resulted in brown-egg layers that are almost as efficient in feed conversion as the white leghorn. In many countries, including European nations, brown eggs are preferred over white eggs. The breeders must be kept in floor management systems to facilitate the breeders’ mating.
From Egg to Layer. Fertilized eggs are transported to commercial incubators for incubation and hatching. After a few days of incubation, the eggs are candled to test for fertility and for viable embryo development. An infertile egg is clear, and a developing embryo shows blood-vessel development. Typically, the eggs are moved to a separate hatching incubator for the final three days of incubation. After hatching, the chicks are vaccinated and sexed, as only the female chicks are useful for egg production. Debeaking (removal of part of the beak) is performed at this time, or after the chicks are seven to ten days old.
The pullets are raised in confinement either on the floor or in cages; outside range rearing is seldom used by commercial breeders. A lighting program is essential for proper development of the pullets. One-day-old chicks receive twenty-three hours of light per day, and for the rest of the growing period, they receive a minimum of ten hours of light per day. They are transferred to laying houses at around sixteen weeks of age. Hens usually begin to lay eggs when they are five months old and continue to lay for about twelve more months.
Egg Production
Several types of management systems are commonly used by egg producers: cages, floor systems, or free-range systems. Cages are used for more than 98 percent of production operations for a variety of reasons. They allow increased population density in the poultry houses, and they are more labor efficient, as feeding, watering, egg collection, and manure removal can all be mechanized. Floor or noncage systems keep hens on litter floors inside buildings that hold feeders, waterers, roosts, and nests. This was the most common management system before the adoption of cage systems. Free-range systems allow hens access to an outdoor yard when weather permits.
The term “organic eggs” refers not so much to a management system but to the feed the hens receive. The feed must be totally vegetarian, the grains used must be pesticide-free, and the hens must not receive hormones or antibiotics.
Because most laying hens produce eggs in windowless houses, artificial lighting is provided. In fact, in all systems, lighting is essential to stimulate the pituitary gland to secrete hormones that help initiate and sustain egg production. Various lighting programs have been developed, but a typical program increases lighting from ten hours at twenty-four weeks of age to seventeen hours at thirty-two weeks and maintains this lighting period until the end of the laying cycle. The length of the lighting period should never be decreased during the laying cycle. The number of eggs produced per hen during a laying cycle can range from 180 to 200 eggs in tropical climates to 250 to 300 eggs in more temperate climates.
In cage systems, after the eggs are laid, they are transported via a conveyor belt to an egg-processing facility, where they are washed, graded for size, and either packed in flats to be shipped to a retail store or broken for further processing.
Breeding Stock. The Institut de Sélection Animale (ISA) holds a dominant position in the egg production industry as it supplies breeding stock for 50 percent of the world’s egg production industry. The company began as Hendrix in the Netherlands, where it still has its headquarters. ISA expanded by purchasing many well-known and respected laying-hen breeding companies, including Babcock, J. J. Warren, Kimber, Shaver, Dekalb, Hisex, and Bovans. Many of these companies began as family-owned businesses in the early part of the twentieth century. Many strains of white and brown egg layers under the names of the original companies are sold as day-old chicks. The chicks destined as breeders must have a good egg-production capability, but good fertility is essential.
Laying Stock. Laying stock is also sold by ISA and other breeders as day-old chicks. ISA has strains of white and brown egg layers that are companions to its breeding stock. High egg production and excellent feed efficiency are essential characteristics for these strains.
Ducks for Egg Production. Ducks have never been popular for egg production in the United States and, like quail eggs, are only a niche market. However, ducks are commonly used in Asia for egg production. The Khaki Campbell breed is best known for egg production, and Metzer Farms sells a hybrid duck that produces eggs at a rate similar to the best chicken egg strains. Duck eggs are larger, have a more deeply pigmented yolk, and have firmer albumen than chicken eggs. Compared with chicken eggs, duck eggs have a higher cholesterol content, tend to pick up off-flavors more readily, and are more susceptible to contamination.
Shell Eggs. Eggs are most commonly marketed in the form in which they are laid, still in their shell. There is no difference in nutritional value between white and brown eggs, and although white eggs have a slightly thicker shell than brown eggs, brown eggshells have a stronger structure, so there is no difference in tendency to break. As the laying cycle nears its end, eggs tend to get bigger with thinner shells, leading to a greater tendency for breakage. When eggs are laid, they are coated with a protective layer called a cuticle. This cuticle is often removed during washing. The shell contains many pores, which nature intended for gaseous exchange for the developing embryo, but which also provide an entry point for bacteria.
The yolk consists of 32 to 36 percent lipids and around 16 percent protein. The lipids include triglycerides (fats), phospholipids, and cholesterol. Triglycerides contain various types of fatty acids. The fatty acid content of yolk can vary according to the diet fed to the hens. A popular modern egg product contains a high content of omega-3 fatty acids, typically 350 milligrams compared with a normal content of 60 milligrams. The eggs also have a lower content of saturated fat, as well as a somewhat lower content of cholesterol. The hens are fed flaxseed to produce these eggs. These eggs have purported health benefits and command a higher price.
Eggs are graded by weight and quality. Egg-processing machinery separates eggs by weight, which can range from jumbo to peewee. Eggs can be grade AA, A, or B in quality. Quality in eggs is determined by candling or breaking them out and measuring albumin height. Grade AA eggs are freshly laid, have a thick, cloudy albumin, and a small air cell. Most eggs in supermarkets are grade A because some time has passed since their laying. Grade A eggs have a larger air cell, and the albumin is clear but thinner. The yolk is more defined in candling but free of defects. Both AA and A eggs can be sold as shell eggs, while grade B eggs are used for further processing. Grade B eggs have poorer quality albumin and minor discoloration or minor blood or meat spots.
Liquid Egg Products. Grade B eggs or other eggs not needed for the shell egg market go to an eggbreaking plant. After breaking, the liquid products obtained include whole egg, egg white, and egg yolk. These products are destined for the food industry and are unlikely to be found in retail stores.
Dried Egg Products. The incentive for developing the technology for drying eggs in the United States began in the 1930’s with the availability of large quantities of eggs from China at a very low cost. The industry got a boost during World War II when the military needed dried eggs. Dried eggs have several advantages over shell eggs or liquid eggs: They can be stored at low cost, take less space to store, are not susceptible to spoilage caused by bacteria, are easier to handle in a sanitary manner, and have lower transportation costs. Dried eggs are used extensively in many products, including bakery foods and mixes, mayonnaise and salad dressings, ice cream, pastas, and convenience foods. Most dried egg products are obtained by spray drying, but before drying, the sugars are removed from the eggs by fermentation or enzymatic treatments. These processes are necessary to avoid reactions of glucose with proteins or phospholipids in the eggs that can result in poor baking qualities or off flavors. The dried egg products are derived from egg white, egg yolk, whole egg, or blends of whole egg or yolk with carbohydrates such as sucrose or syrups.
Specialty dried egg products include a scrambled egg mix that has good storage capability and low-cholesterol egg products. Most low-cholesterol egg products contain egg white, with nonfat milk, vegetable oil, and pigments substituting for yolk. The final composition is similar to that of a whole egg.