“Factory farming” is any high-output farming system for animals. Factory farms are sometimes called concentrated animal feeding operations (CAFOs) or macro-farms. Most food animals are now intensively farmed, including all kinds of species from cows to fish.

The industry’s defining characteristic is that it prioritizes output above all else, often including product quality, workers’ safety, the environment, human health, and animals themselves.

Conditions may differ slightly depending on the farm, location, and animal species, but by definition a CAFO involves unnatural, cramped conditions. Disease, pharmaceuticals, and animal cruelty are common enough to also be considered typical aspects of factory farming.

The History Of Factory Farming

Factory farming is a relatively recent phenomenon. Its development began with the mechanization of pig slaughter in the 1930s, followed by advanced chicken-rearing techniques, large-scale packing plants, and rapidly growing poultry farms in the 1950s.

CAFOs gained major traction in the 1960s as a potential route to food sovereignty, and high-output farms were rewarded with subsidies and favorable policies. In the 1970s, US Agriculture Secretary Earl Butz famously told the nation’s farmers to “get big or get out.”

By the 1980s, overproduction and various other economic factors meant that a large number of independent American farmers could no longer stay afloat, creating further opportunities for corporate involvement in the sector. In 1990, small to medium-sized farms accounted for nearly 50 percent of US agriculture, but that number has now fallen to less than 25 percent.

As of 2024, approximately 99 percent of farm animals in the US - and 85 percent of all farm animals in the UK - live within CAFOs. Global estimates are tricky, but it's likely around 74 percent of the 100 billion animals killed for food or products every year are factory-farmed. Both the US and UK have seen a recent sharp rise in the number of sprawling “megafarms.”

Proponents of factory farming claim that expansion is necessary to feed a growing global population with a growing hunger for meat and animal products. Critics argue that factory farming is not sustainable or effective, and that expansion is not a solution. Factory farming already has a significant negative impact on the environment, animals, and humans that will only grow with any further expansion.

Factory Farming and the Environment

CAFOs poison the air, the land, the water, and the atmosphere, harming ecosystems far beyond their immediate vicinity. The industry’s environmental footprint is enormous, far-reaching, and devastating for plants, animals, and humans around the world.

Factory farming produces greenhouse gas emissions (GHGs) at every stage, from the CO2 emitted by industry-caused deforestation to the millions of tons of methane emitted by factory-farmed cows, pigs, and other ruminant animals. Factory farms are responsible for 37 percent of global methane emissions, and 65 percent of all toxic nitrous oxide emissions.

The massive quantity of animal waste produced by CAFOs emits this nitrous oxide along with around 400 different harmful gases into the atmosphere. Manure lagoons and waste-laden rain (agricultural run-off) poison the earth’s water, with the UK’s industry alone producing over 50,000 tonnes of untreated excrement every single day. Manure lagoons can kill wildlife and people and will be increasingly likely to spill as the climate crisis worsens.

Agricultural run-off from CAFOs is also responsible for extensive land degradation. A report by Four Paws found that industrialized animal farming in the EU causes 80 percent of soil acidification and 47 percent of nitrogen pollution to coastal waters, which in turn causes algae blooms and other problems in the marine environment.

Overall, the extreme inefficiency of feeding edible crops to animals to produce protein - even when intensively farmed in CAFOs - causes additional harm. One kilogram of beef requires over 14,000 liters of water and 8 kg of feed, and every 100 calories of crops used to farm animals produces just 40 calories of milk, 12 calories of chicken, and three calories of beef.

The Ethics of Factory Farming

The above metrics are useful in highlighting the inefficiency of factory farming in food production, but animals are more than the sum of their kilograms and calories. Recently, changing attitudes to animal sentience - historically eschewed by mainstream science - have led to animal consciousness becoming an accepted and legitimate avenue for study.

In the Compassion in World Farming (CIWF) report Recognizing the Sentience of Farm Animals, the authors write that “most scientists and philosophers, and most of the general public, accept that animals are sentient.” However, they also note that how animals are treated does not always reflect this acceptance, a common form of “cognitive dissonance.”

For example, while animal sentience has now been enshrined in UK law, there have been no moves to clamp down on the cages and crates used in the factory farming of chickens and pigs. Cows demonstrate complex interpersonal relationships and can live for up to 30 years, but are still slaughtered between 18 months old (beef cattle) and five years old (dairy cattle).

Factory farming depends on crowded, high-stress living environments. The animals on CAFOs typically do not have the physical space to practice natural behaviors like nesting, foraging, and play, causing great loss of well-being. Animals are separated from friends and family, and cause injuries to themselves and each other out of fear, frustration, and stress.

Some animals may have their teeth clipped, tails docked, horns removed, beaks trimmed, and suffer other sedative-free surgeries, largely to boost productivity and prevent issues caused by intensive farming itself. Even in Europe, where the routine tail docking of pigs is illegal, CIWF reports that the practice has been carried out on over 90 percent of the farmed population. 

Cruel or unreliable slaughter methods are rife on factory farms, as are instances of abuse and live animal transportation, even on so-called sustainable, high-welfare farms. These realities of factory farming are, arguably, incompatible with recognized animal sentience.

Factory Farming and Human Health

The cramped conditions, concentrated feed, and selective breeding in CAFOs all increase the likelihood of diseases and other health problems amongst factory-farmed animals. About 60 percent of all modern novel epidemics are zoonotic in origin, meaning they were transmitted between humans and animals or vice versa. This includes COVID-19.

A report published in Science Advances describes the “infectious disease trap” of animal agriculture, in which the industry promotes the spread of zoonotic diseases through deforestation, “intensive management,” and poor waste management.

The industry attempts to mitigate disease risk with the routine use of medicines and antibiotics, and some farmers use them to further promote rapid growth. These drugs enter the environment via agricultural runoff, thereby increasing antimicrobial resistance in the wider world and significantly increasing the risk of widespread infection in humans.

The EU has already banned the standard use of such medicines, but factory farms in other countries still medicate as routine. Around 80 percent of all antibiotics sold in the US are used in animal agriculture, and 70 percent of those are deemed “medically important.”

As of 2024, the overuse of antibiotics and other medicines in animal agriculture is a leading cause of antimicrobial resistance (AMR) in humans, causing millions of deaths each year.

Factory Farming and Human Rights

The pollution from factory farms can be truly debilitating for those who live nearby. In a recent photo essay for the Guardian, Selene Magnolia Gatti documented how CAFOs impact local communities through noise pollution, smells, chronic infections, and disease.

The industry is inhospitable to its workers, too, who carry out extremely dangerous, traumatic, and often exploitative work. Most CAFO farmers are “contract growers,” meaning they take on the work and risks of factory farming animals. Meanwhile, farm owners dictate methods and reap the financial rewards, per the Animal Legal Defence Fund (ALDF).

According to the ALDF, many of the workers on American factory farms are refugees, while up to 33 percent are migrants and 25 percent are undocumented, making them particularly vulnerable to exploitation. It is thought that human cases of the ongoing multi-state outbreak of bird flu amongst dairy cows may be going unreported in part due to worker vulnerability.

Finally, factory-farmed meat comes with an inherent risk to consumers. Studies indicate that meat produced on CAFOs is less nutritious than higher welfare animal products, which itself is thought to be less healthy than nutritious plant-based alternatives. Overall, factory-farmed products are also far more likely to contain gastroenteritis-causing pathogens.

What Can Be Done About Factory Farming?

The current global food system is unfit for purpose, and factory farming, in particular, continues to grow despite its failure as a means of food production. As stated by the UN Environment Programme (UNEP), the way the current system “churns out food” drives climate change, biodiversity loss, and pollution, and leaves nearly 700 million people hungry.

For consumers, boycotting factory-farmed products as much as possible will help to reduce demand and decrease humanity’s collective reliance on intensive farming for cheap meat. Historically speaking, meat is a luxury item, and purchasing higher quality, sustainable, high-welfare, and nutritious animal products less often will help support small farms.

Meat-free Mondays or One Meal A Day are simple, structured ways to reduce meat consumption overall, with potentially significant results for health and the planet. Supporting sustainable agriculture in place of CAFOs could also include shopping for produce locally and supporting diversified farms that use regenerative agriculture.

Technology also provides some extremely efficient alternatives to factory farming and traditional agriculture. Recent breakthroughs in precision fermentation and other cutting-edge food tech mean that plant proteins and even cultured meat could be scalable in the near future. Meanwhile, hydroponics and vertical farming can reduce the quantity of land and water required to grow fresh produce, further streamlining the food system.

Correcting the issues of factory farming will likely require effective, comprehensive state intervention. Government subsidies overwhelmingly promote animal agriculture and reward output. Updating these schemes to incentivize sustainability would make a significant difference, as would punitive legislation around environmental damage and animal cruelty.