Most chickens raised in factory farms spend their entire lives indoors in crowded sheds or cages, bred to grow so fast their bodies struggle to keep up. The conditions vary depending on whether a bird is raised for meat (broilers) or eggs (layers), but both systems prioritize production speed and efficiency over the animals’ comfort or natural behavior.
How Fast Broilers Grow
Modern broiler chickens have been selectively bred for decades to put on weight at extraordinary speed. A comparison between a modern broiler line and a heritage line unselected since the 1950s, published in Poultry Science, found that the modern bird’s breast muscle made up 18% of its total body mass at five weeks old, double the 9% seen in the heritage line at the same age. That kind of growth means today’s broilers reach slaughter weight in roughly six to seven weeks, about half the time it took birds in the mid-20th century.
This rapid growth comes at a cost. The birds’ hearts, lungs, and legs often can’t keep pace with their ballooning bodies. A condition called pulmonary hypertension syndrome, where fluid accumulates in the abdomen, occurs more frequently in fast-growing birds. Research on genetic selection shows a clear link: breeding for heavier body weight simultaneously increases a bird’s susceptibility to this heart-lung disorder. Many broilers also develop leg problems that limit their ability to walk, stand, or reach food and water.
Life Inside a Broiler Shed
Broiler chickens are raised in large, windowless sheds that can hold tens of thousands of birds at a time. The global industry standard packs birds at densities of 30 to 38 kilograms of body weight per square meter, which translates to roughly 20 adult birds per square meter at slaughter age. To put that in perspective, each bird gets about the area of a standard sheet of paper. Research published in PLOS One found that even 15 birds per square meter compromised feed intake and weight gain, suggesting the standard commercial density is well above what the birds can comfortably tolerate.
The floors of these sheds are covered in litter, typically wood shavings, that absorbs droppings over the flock’s entire lifespan. As the litter degrades, it releases ammonia. Concentrations above 25 parts per million irritate the birds’ eyes and respiratory systems, reduce feed intake, slow growth, increase vulnerability to infectious disease, and can cause death. The same air quality affects farm workers. Despite these known thresholds, ventilation in large-scale sheds doesn’t always keep ammonia below safe levels, particularly in warmer weather or toward the end of a grow-out cycle when the birds are largest and producing the most waste.
Wet, ammonia-rich litter also causes direct injuries. Footpad dermatitis, essentially chemical burns on the bottom of the feet, affects up to 65% of fast-growing broiler flocks by slaughter age. Hock burns, similar lesions on the joint where the leg rests against the ground, reach severe levels in as many as 41% of birds in some flocks. Because these heavy, fast-growing birds spend much of their time sitting, their skin stays in prolonged contact with deteriorating litter.
Lighting That Controls Behavior
Factory farms manipulate lighting to regulate how much chickens eat, sleep, and move. Some operations have historically kept lights on nearly around the clock to encourage continuous feeding. A common intensive schedule uses repeating cycles of three hours of light followed by one hour of darkness. Research in Poultry Science found that a 16-hour light, 8-hour dark cycle improved welfare by allowing birds uninterrupted rest during the dark phase. That schedule is now recommended as a baseline for broiler production, though actual practices vary by operation and country. Birds raised under near-constant light show higher stress and weaker immune function.
How Egg-Laying Hens Are Housed
Egg-laying hens face a different set of conditions. In conventional cage systems, which still house the majority of the world’s laying hens, birds are kept in small wire enclosures called battery cages. Each hen typically gets between 430 and 560 square centimeters of floor space, less area than a single letter-sized piece of paper. The wire flooring prevents hens from dustbathing, scratching, perching, or nesting, all behaviors that are instinctive and important to their welfare. Many hens lose feathers from rubbing against the cage wire and from stress-related pecking by cagemates.
To reduce the damage birds inflict on each other in these tight quarters, most egg-laying hens have their beaks trimmed. According to a USDA fact sheet, the most common method in the United States uses a heated blade at 650 to 750 degrees Celsius, applied when chicks are 5 to 10 days old. The blade cuts and cauterizes the beak tissue simultaneously. A newer method uses infrared treatment at the hatchery on day-old chicks. Beak trimming reduces injurious pecking but removes sensitive tissue and can cause chronic pain, particularly when performed with the hot-blade method.
What Happens to Male Chicks
In the egg industry, male chicks have no commercial value. They don’t lay eggs, and because layer breeds grow too slowly to be raised profitably for meat, male chicks are killed on their first day of life at the hatchery. The standard methods are maceration (a high-speed grinder) and gassing. Billions of male chicks are culled globally each year. Some countries, including Germany and France, have moved to ban the practice by requiring producers to determine the sex of embryos before they hatch, but these technologies are still being scaled and are not yet standard worldwide. Other proposed alternatives include breeding dual-purpose chickens that can be used for both eggs and meat, though these birds are less productive in both categories than specialized breeds.
Slaughter Process
At slaughter, broilers are typically shackled upside down by their legs on a moving line and passed through an electrified water bath intended to stun them unconscious before their throats are cut. Research on optimizing these systems found that a minimum stunning time of four seconds per bird is needed, with four birds submerged in the water simultaneously. The electrical parameters matter: at lower currents (around 30 milliamps per bird), stunning may be ineffective, leaving birds conscious when they reach the neck-cutting blade. Higher currents of around 200 milliamps per bird at 750 hertz were found to reliably render birds unconscious without damaging meat quality.
Line speeds in commercial plants can process well over 100 birds per minute. At that pace, errors are inevitable. Some birds miss the stunner, arriving at the blade fully conscious. Others miss the blade entirely and enter the scalding tank, used to loosen feathers, while still alive. Controlled atmosphere stunning, which uses gas mixtures instead of electrical water baths, is considered more humane and is gaining adoption in some regions, but electric water-bath stunning remains the dominant method globally.
The Scale of the System
What makes factory farming distinct from smaller operations isn’t any single practice but how all of these conditions interact at massive scale. A single shed may hold 20,000 to 30,000 broilers. A single laying operation may cage hundreds of thousands of hens. The economics of producing cheap chicken meat and eggs drive every design choice: the genetics that maximize breast meat yield, the stocking densities that fill every square meter, the lighting schedules that push feed conversion, and the slaughter speeds that process birds as fast as possible. Each bird’s experience is shaped by a system built around volume and cost, with welfare considerations running secondary to production targets in most commercial operations worldwide.