Egg Production

Summary

The egg-production field includes farm production of shell eggs for direct consumption and further processing of eggs for use in products of the food industry. Egg production includes the development of highly productive breeds of laying hens, advances in technology in the production and processing of eggs, and business models that permit the efficient production and marketing of eggs.

Definition and Basic Principles

Egg production in the United States has undergone a remarkable transformation. Before the twentieth century, hens ran loose around farmyards, largely fending for themselves. Around the late 1800s, 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 the application of important management principles, such as proper feeding, breeding, and egg collection.

The next major advance took place around the 1960s, 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 for factory farming and have raised questions of animal welfare that must be addressed by the producer.

Background and History

Chickens were probably domesticated from red junglefowl in Southeast Asia. Genetic studies suggest multiple sites of domestication, including China and India. Archaeological studies indicate that chickens were present in the Americas before the time of the Spanish conquistadors.

The modern egg industry is a result of a series of technological advances. In the 1870s, fowl operations began to use incubators to hatch chickens, rapidly increasing the number of commercial hatcheries. Poultry breeders applied scientific principles to develop improved breeds and strains of chickens for egg production. Land-grant colleges engaged in research in poultry nutrition and feeding, which led to improved management practices and more efficient production of eggs. Better understanding and treatment of diseases, together with improved sanitation and ventilation, allowed for the creation of confinement systems.

Improved distribution systems and the development of new egg products led to greatly increased consumption of eggs in the United States, reaching a maximum of 402 eggs per capita in 1945. Health concerns about the cholesterol content of eggs and changes in lifestyle led to a decline in consumption to a low of 230 eggs per capita in 1991. However, after the publication of scientific studies showing that consuming eggs does not raise blood cholesterol, consumption of eggs began to increase again. In 2023, per capita egg consumption in the United States was just over 281.

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. Very few breeding companies dominate the supply of egg-production chicks, and they have their own specialized lines or strains of breeders. The breeders must be kept in floor management systems to facilitate the breeders' mating.

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.

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, or viewed with a light shining into them, to test for fertility and 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 often performed at this time or after the chicks are seven to ten days old. This procedure is meant to prevent chickens from harming one another, but many animal welfare groups oppose the practice.

The pullets are raised in confinement on the floor or in cages; commercial breeders seldom use outside-range rearing. A lighting program is essential for the proper development of the pullets. One-day-old chicks receive twenty-three hours of light per day; 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 90 percent of production operations for various 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 non-cage 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 or free-roaming systems allow hens access to an outdoor yard when weather permits.

In 2015, the fast-food giant McDonald's announced that it would gradually switch from using conventionally farmed eggs to cage-free eggs in their products. Although the company's orginal target date was 2025, they achieved this goal by 2023. Other fast-food chains and food companies soon followed suit, greatly boosting the market for cage-free egg-laying hens in the United States. By the mid-2020s, 40 percent of all table egg layers in the country were cage-free and demand continued to grow. Furthermore, the variety of cage-free labels has grown. According to the American Society for Prevention of Cruelty to Animals (ASPCA), in addition to free-range eggs, labels include “animal welfare approved,” “certified humane,” “gap 5-step program,” and “American humane certified.” Each label denotes different requirements for using cages, minimum indoor space, perches, nest boxes, dust-bathing, and outdoor access.

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. However, eggs labeled “certified organic” or “USDA organic” by the United States Department of Agriculture (USDA) must also be cage-free.

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 in tropical climates and 250 to 300 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.

Applications and Products

Breeding Stock. The Institut de Sélection Animale (ISA) holds a dominant position in the egg-production industry, supplying breeding stock for nearly 50 percent of the industry worldwide. The company began as Hendrix in the Netherlands, where it maintains 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 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. ISA and other breeders also sell laying stock as day-old chicks. ISA has strains of white and brown egg layers that are companions to its breeding stock. These strains have high egg production and excellent feed efficiency.

Ducks for Egg Production.Ducks have never been popular for egg production in the United States, and duck eggs, like quail eggs, are only a niche market. However, duck eggs are commonly consumed in parts of Asia. 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. They also 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 as how 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 the tendency to break. As the laying cycle nears its end, eggs tend to get bigger and have 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 intended for gaseous exchange in the developing embryo but also provides 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 of the hens. A popular modern egg product contains a high content of omega-3 fatty acids, typically 350 milligrams, compared to a normal content of 60 milligrams. The eggs also have a lower content of saturated fat and a somewhat lower cholesterol content. 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 grades AA, A, or B in quality. Egg quality is determined by candling or breaking them out and measuring albumin height. Grade AA eggs are freshly laid and 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, 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 egg-breaking 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 1930s 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; before this, 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 with good storage capability and low-cholesterol egg products. Most low-cholesterol egg products contain egg whites, with nonfat milk, vegetable oil, and pigments substituting for yolks. The final composition is similar to that of a whole egg.

Careers and Course Work

Coursework in poultry science is basic for students interested in pursuing a career in egg production. Because most poultry science departments have been absorbed into animal science departments at land-grant universities, students should carefully search the curriculum, staff, and programs in these departments to determine if they can provide an adequate focus on egg production and technology.

Suitable undergraduate coursework in the field of concentration could include poultry or laying hen production, poultry nutrition, poultry diseases, poultry anatomy and physiology, and reproduction (including breeding, embryonic development, and hatching). Students interested in the egg products industry should consider coursework in food science. Supporting coursework could include farm management, biology, and business courses such as economics and accounting.

Career opportunities for students with a bachelor's degree include poultry farm manager (as owner or employee), feed mill or hatchery manager, and salesperson for feeds, breeding or production stock, or equipment.

Students interested in a research career in poultry breeding or nutrition will need to complete graduate work leading to a doctorate degree. Advanced courses in animal breeding, statistics, endocrinology, genome analysis, genetics, and biochemistry could be taken. Professional poultry scientists can obtain employment in academia or industry.

Social Context and Future Prospects

The modern cage system of egg production is a marvel of efficiency and low cost. However, the nature of the system has been brought to the attention of animal welfare activists. The hens are kept in very crowded conditions (typically sixty-seven square inches per hen) and cannot perform their natural or instinctive behaviors, such as sleeping on roosts, laying eggs in nests, and taking dust baths. Animal activists say this is not humane; egg producers reply that hens kept in cage systems are healthier than those raised in other systems, noting that their productivity is higher. Animal science departments have been aware of these criticisms and have developed the field of farm animal welfare. Animal welfare can be studied scientifically in an objective, reliable, and reproducible manner.

In the meantime, the demand for answers to animal welfare concerns has resulted in legislation banning the use of battery cages for egg production in some jurisdictions, including the European Union. In California, the ballot initiative Proposition 2 was approved by voters in 2008 and went into full effect on January 1, 2015, mandating that all eggs produced in the state come from hens who have sufficient room in their cages to turn around, lie down, and extend their wings fully. In 2010, California further legislated that all eggs sold in the state comply with Proposition 2, even if the eggs were laid elsewhere. By 2023, nine other states had passed similar laws, including Washington, Oregon, Rhode Island, and Michigan.

Egg consumption fell in the late twentieth century because eggs have high cholesterol levels. Still, consistent research showed that egg consumption did not increase blood cholesterol in healthy people. (Persons with heart disease may want to consult their physician, as their bodies may handle cholesterol differently.) The image of eggs suffered, and egg producers worked to convince the public of the egg's nutritive value. As a result, US egg consumption increased again in the early twenty-first century, although by the mid-2020s, it had not reached its 1945 peak. Egg consumption did increase with the popularity of diets that limit carbohydrate intake. 

A problem with eggs is possible salmonella contamination. If the shells are contaminated with salmonella, proper washing can eliminate this hazard, but if hens become infected with salmonella during the growing period, the eggs are internally contaminated. Producers have occasionally been forced to recall eggs due to potential contamination, such as an incident in August 2010 affecting more than five hundred million eggs produced by Wright County Egg and Hillandale Farms of Iowa. Programs are being developed to certify hens in large flocks as being salmonella-free.

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