Commercial chicken production is a tightly controlled process that takes a bird from egg to market weight in as few as 35 days. Whether raised for meat (broilers) or eggs (layers), chickens move through distinct stages: selective breeding, incubation, hatching, feeding through rapid growth phases, and processing. Here’s how each stage works.
Breeding and Genetic Selection
Modern commercial chickens bear little resemblance to their ancestors. Decades of selective breeding have produced specialized strains optimized for either meat or egg production. The two most widely used meat breeds globally are the Cobb 500 and the Ross 308, chosen for their fast growth and efficient feed use. In a side-by-side comparison, Cobb 500 birds reached an average of 3.15 kg (about 6.9 pounds) per bird by six weeks, while Ross 308 birds reached 2.62 kg (5.8 pounds) over the same period.
These aren’t breeds you’d find at a farm supply store. Primary breeding companies maintain closely guarded “grandparent” and “parent” flocks. Parent birds are mated to produce the fertilized eggs that become the broiler chicks raised on farms. This tiered system means the genetics of nearly every commercial chicken trace back to just a handful of corporate breeding programs.
Incubation and Hatching
Fertilized eggs are collected from parent flocks and transported to hatcheries, where they’re placed in large forced-air incubators. The target temperature is a steady 100°F for the entire 21-day incubation period, with relative humidity held between 58 and 60 percent for most of that time. During the final three days, humidity is raised to 65 percent or higher to help chicks break through the shell. Eggs are mechanically turned at regular intervals to prevent the developing embryo from sticking to the shell membrane, but turning stops after day 18 to let the chick settle into hatching position.
Industrial hatcheries can incubate hundreds of thousands of eggs at once. Once chicks hatch, they’re sorted, vaccinated, and shipped to grow-out farms, typically within 24 hours. Newly hatched chicks can survive this transit period because they absorb the remaining yolk sac just before hatching, which provides enough nutrition for roughly 48 to 72 hours.
How Meat Chickens Are Raised
Broiler chicks arrive at grow-out houses as day-old birds and are raised to market weight in about 35 to 42 days, depending on the target size. A typical commercial operation aims for a final weight between 1,500 and 2,200 grams (3.3 to 4.8 pounds) in a 35-day rearing period, though birds grown for larger cuts or whole roasters may be kept a few weeks longer.
Feeding happens in phases. Chicks start on a high-protein “starter” feed designed to support rapid early growth, then transition to a “grower” feed, and finally a “finisher” feed that’s higher in energy and lower in protein. The goal is to maximize the feed conversion ratio, which measures how efficiently a bird turns feed into body weight. Modern broilers convert feed at a ratio of roughly 1.6 to 1.8, meaning it takes about 1.6 to 1.8 pounds of feed to produce one pound of live weight gain. That ratio worsens as birds get older and larger, climbing above 2.0 in the final week before processing.
Birds are raised in enclosed houses that can hold 20,000 or more chickens at a time. Temperature, ventilation, lighting, and water delivery are all automated. Lighting schedules are carefully managed because light exposure affects how much birds eat and how quickly they grow.
How Egg-Laying Hens Are Raised
Layer hens follow a completely different timeline. Pullets (young hens) begin producing eggs between 18 and 22 weeks of age when they receive 14 to 16 hours of light per day. Peak production occurs during the longest daylight periods, and commercial houses use artificial lighting to simulate ideal conditions year-round.
Egg production stays high for the first year or so but gradually declines. Most commercial layer operations keep hens for two to three years before replacing the flock. Backyard hens, by comparison, can live six to eight years and often produce eggs for three to four years, though at lower rates. When commercial hens are retired from production, they’re typically processed into lower-value products like soups, pet food, or rendered meal, since their meat is tougher than that of broilers.
Biosecurity on the Farm
Disease can devastate a flock of thousands in a matter of days, so biosecurity protocols are central to commercial production. The U.S. Department of Agriculture’s “Defend the Flock” program outlines the standard practices most operations follow. Visitors are kept to a minimum, and anyone entering a poultry house is expected to wear disposable boot covers or use disinfectant footbaths, with all manure and debris scrubbed off footwear before stepping into the bath. Workers change clothes before entering and exiting poultry areas, and protective coveralls, boots, and headgear are standard.
Equipment, vehicles, and tools that have contacted birds or droppings must be cleaned and disinfected before leaving the property. Items that can’t be properly sanitized, like cardboard egg flats, are not reused or moved between facilities. These measures are especially critical during outbreaks of avian influenza, which has caused mass flock losses in recent years and prompted stricter enforcement of biosecurity standards.
Antibiotics and Regulation
The FDA no longer permits the use of medically important antibiotics for growth promotion in poultry. Under guidance finalized over the past decade, all antibiotics classified as medically important to human medicine must now be used under veterinary oversight and only for disease prevention, control, or treatment. This means producers can’t simply add antibiotics to feed or water to make birds grow faster, a practice that was common for decades and contributed to concerns about antibiotic-resistant bacteria. Many large poultry companies have gone further, marketing “no antibiotics ever” product lines in response to consumer demand.
Environmental Footprint
Chicken has a significantly smaller carbon footprint than beef or pork, which is one reason global production has grown so rapidly. A lifecycle analysis of chicken meat production found emissions of approximately 4.08 kg of CO2 equivalent per kilogram of chicken. For comparison, beef typically generates 20 to 30 kg CO2-eq per kilogram, and pork falls in the range of 5 to 7 kg.
The biggest contributor to chicken’s carbon footprint isn’t the farm itself. Feed production accounts for nearly 57 percent of total emissions, driven largely by the land, fertilizer, and transportation needed to grow corn and soybean meal. The chicken production phase on the farm is the second-largest contributor, followed by slaughtering and processing, with distribution transport contributing the least.