The Scale and Consequences of Industrial Animal Agriculture

Recent decades have seen rapid urbanization and social change worldwide and drastic changes to the traditional relationships between humans and animals. Globally, many communities still rely on traditional methods of raising animals for food, clothing, and labor. Yet the reach of industrialized, intensive animal agriculture is expanding worldwide. Increasing numbers of animals are bred and slaughtered in extreme confinement each year by the agribusiness industry. Industrial animal agriculture drives some of the greatest animal welfare, human rights, and environmental concerns of this epoch.


Animal agriculture is the practice of breeding and raising animals for food, fiber, labor, and other products. Before the twentieth century, animals on US farms routinely had access to the outdoors and sufficient land for grazing and foraging, and they reproduced in seasonal cycles. Most farms were small-scale, family-owned, and raised more than one animal species.

Over the last century, animal agriculture in the US has shifted almost exclusively to large-scale, specialized industrial operations that confine and feed thousands of animals in indoor spaces.[1] These operations are colloquially referred to as factory farms, and more technically as concentrated animal feeding operations (CAFOs).

In the 1930s, the poultry industry developed a chicken confinement system that enabled the processing of many more birds and continuous rather than seasonal production. The meat and feed industries, with help from USDA, built societal demand by aggressively marketing chicken to US consumers. As they grew, chicken producers pioneered indoor confinement methods and selectively bred chickens to grow larger, faster. Vertical integration of supply chains from feed production to meat retail allowed producer brands to grow into agribusiness giants.

Vertical integration, coupled with intensive production methods, paved the way for the industrialization of US animal agriculture.[2] The beef, dairy, and pig industries followed the example of poultry producers, separating animals from natural landscapes and breeding cycles. Antibiotics and other technological advances, like mechanization and artificial insemination, normalized the reproduction of animals year-round in high-density conditions.


The US is the world’s leading producer of chicken. Overall nearly 9 billion chickens are killed annually in the US, and there are distinct production chains for meat and eggs.

Young chickens bred for meat production, called broilers, account for nearly all US chicken consumption.[3] They are born in hatcheries from artificially inseminated birds, then moved to grow-out operations until they reach slaughter weight. Grow-out operations are large, artificially ventilated sheds with litter-covered floors, which are not usually cleaned until one group of birds is slaughtered and the next cohort arrives. The average stocking density of broiler sheds allows only 0.5–1 square foot of space per bird.

Laying hens are born in hatcheries and separated by sex. Male chicks are killed soon after hatching,[4] while female chicks are moved into production housing at twenty weeks old and confined to wire cages holding seven to eight birds. Their laying cycle continues until their laying slows at around seventy-two weeks, after which they are sent to slaughter. In 2020, 325 million commercial laying hens produced over 96 billion eggs for consumption.


Cattle farming includes both dairy and beef production systems. The US is the world’s second-largest milk producer and the leading beef producer.

The US dairy industry includes over 9 million cows producing milk for human consumption. Over the past two decades, the dairy industry has followed a consistent trend of increasing overall milk production, larger herds per farm, and fewer and fewer farms.[5] The population of dairy cows has decreased by almost 3 million since 1970, but milk production per cow doubled over that same time, meaning modern cows are now producing vastly more milk annually than their ancestors.

Dairy cows are impregnated using artificial insemination at around fifteen months old and have their first calf at twenty-four months. The calf is removed from its mother within hours of birth, and the mother’s milk is repurposed for human consumption. Female calves are raised on milk replacer and grown until they are old enough to breed, while male calves are often sent to live auctions to supply the beef and veal industries.[6]

Dairy cows average three pregnancy and lactation cycles and remain with the herd for around five years, after which they are sent to slaughter. They may be sent to slaughter earlier if they experience udder infections, decreased milk production, lameness, or infertility. Most dairy cows are housed indoors without pasture access, fed and watered using automatic processes, and milked by mechanized milking carousels. Tie stalls are commonly used on 39% of dairy farms, impeding the movement of dairy cattle and preventing social interaction.[7]

Over 31 million cows are raised for beef and other meat products in cow-calf operations that often allow cows to graze on pasture. Calves are weaned at three to seven months and sold to feedlots—barren fenced outdoor areas that intensively confine up to 32,000 cattle at a time. These cattle are fed until they reach market weight and are then transported to slaughter.


The US is the world’s third-largest pork producer. Nearly 75 million pigs are raised on US farms, and the vast majority spend their entire lives inside CAFOs. Breeding sows are often kept in cramped gestation crates during their pregnancies. After birth, sows are typically confined in farrowing crates that hold the sow in place for nursing, a control measure implemented by farmers to prevent newborn piglets from being crushed by the sow. These barred metal crates are barely larger than the sow and prevent her from turning around or interacting with her piglets.

Piglets are weaned at twenty-one days and moved to a wean-to-finish facility, where they grow to around 50 pounds before being transferred to indoor finishing operations until they reach 280 pounds. Approximately 100 million pigs are slaughtered annually in the US. When they are killed at six to seven months old, these pigs have usually been transported from one intensively confined barn to another without ever stepping outdoors.


The US ranks second in turkey consumption globally and is the largest exporter of turkeys. As in the chicken meat and egg industries, turkey production is dominated by vertical integration and intensive CAFO housing. Turkeys face many of the same welfare issues as broiler chickens due to being bred for rapid growth and raised in continuous confinement.

Although rabbits are not necessarily considered agricultural animals, rabbit consumption was popular in the US up until the 1960s and has seen a recent resurgence. There are more than 4,000 rabbit farms selling 500,000 rabbits annually for meat consumption, breeding, and angora wool.

Aquaculture is another form of animal agriculture in the US that replicates underwater many of the welfare and environmental concerns of terrestrial CAFOs. Fish like catfish, trout, and salmon are intensively farmed in concentrated aquatic animal production (CAAP) facilities. The US ranks 17th in global aquaculture production, and fish farmers produced 680 million pounds of saltwater and freshwater fish in 2018.


Certain forms of high-welfare animal agriculture can support human nutrition in balance with local environments and traditional land management customs. Traditional subsistence farming may include small levels of locally adapted animal production in low-density outdoor environments that limit environmental impacts and allow for animals to exhibit natural behaviors, though ethical considerations related to eating animals remain. Such forms of animal agriculture can play a role in sustainable practices integrated into local ecologies and landscapes.

However, large-scale commercial industrialized animal agriculture—the antithesis of traditional animal husbandry—has become increasingly dominant in the global food system and raises significant welfare, economic and environmental concerns. Industrial animal production is designed to maximize profit from endemic animal cruelty, negatively impacts human health and food justice, and is responsible for significant environmental pollution, including a large share of human greenhouse gas emissions.


In industrial agriculture, animals are units of production maximized for profit, resulting in inherently cruel practices that fail to recognize the need for species-specific, natural behaviors. In addition to intensive indoor production conditions, inhumane slaughter practices routinely cause additional animal suffering.


The abnormally fast growth of broiler chickens stresses their musculoskeletal systems, and they suffer from myopathies, deformities, degenerative joint diseases, ruptured tendons, gout, and leg fractures. These disorders cause high levels of pain and suffering, and decreased mobility inside crowded CAFO enclosures can result in death by dehydration or starvation.[8]

Despite recent gains in cage-free commitments, over 70% of laying chickens are still housed in conventional wire cages, sometimes called battery cages, that deprive chickens of the ability to perch, dust bathe, forage, escape from aggression, and flap their wings. Crowded birds are unable to express natural behaviors like preening, scratching, and resting, which leads to frustration and aggression. Poor air quality due to ammonia build-up from soiled litter causes respiratory and eye ailments, and contact with wet litter results in skin irritation.[9]

Laying hens produce eggs at unnaturally high rates, depleting their bodies of needed minerals and nutrients.[10] Coupled with constant confinement and lack of exercise, nutrient deficiencies cause rickets, osteoporosis,[11] and caged layer fatigue—a metabolic disease leading to leg paresis and immobility. Feather pecking is a frequent welfare problem noted in intensive housing of laying hens and can lead to cannibalism, debilitating injuries, and mortality. In an attempt to reduce feather picking and aggression, the tips of hens’ beaks are routinely removed with hot blades, a procedure that causes acute and chronic pain.[12] The methods used for culling male chicks in the egg industry also raise concerns about pain and suffering.


Dairy cows are subjected to repeated cycles of pregnancy and lactation. The high demands placed on their bodies lead to diseases like hypocalcemia, metritis, mastitis, and ketosis.[13] Continuous indoor housing prevents normal behaviors like grazing and cud-chewing, and hard concrete floors contribute to lameness and foot disease.[14]

The abrupt removal of calves from their mothers causes emotional distress for both, and calves show negative emotional states and cognitive defects after early weaning.[15] Both dairy and beef calves are subjected to painful management practices without analgesia, including castration and dehorning, that result in negative emotional states.[16]

Beef cows experience rapid diet changes as they move through stages of the production chain, leading to illnesses like bovine laminitis, and sudden mixing with other cows at feedlots increases the risk of sickness and death from respiratory diseases. Beef cows also experience painful branding, extremes of cold and heat, wet conditions, and prolonged transport times.[17] 


Common intensive management procedures like castration, tail amputation, tooth clipping, and ear notching that are practiced to support high-density indoor housing cause significant pain and create infection risks.[18] Diarrheal diseases often contribute to the death of piglets,[19] and older pigs experience lameness, foot and claw disorders, and joint weakness from confinement.[20]

Farrowing crates severely restrict movement. Sows are unable to express normal maternal behaviors, and they also experience shoulder injuries and pressure sores, lameness, and udder wounds.[21] All pigs in CAFOs are deprived of necessary outdoor behaviors for welfare, such as wallowing and rooting.


All forms of large-scale animal agriculture impact the global climate, though some animal species and some forms of production contribute exceptionally high amounts of greenhouse gas (GHG) emissions.

Cattle raised for beef and dairy emit around 65% of the animal agriculture sector’s total greenhouse gas output, arising from the production and processing of animal feed and emissions from the animals’ digestion. Animal agriculture is responsible for a minimum of 16.5% of all greenhouse gas emissions worldwide.[22] Emissions from animal agriculture operations in the US have increased by over 20% in the past three decades.

While cattle produce the most agricultural greenhouse gas emissions overall, pigs and layer chickens are the second and third highest emitters, respectively. CAFOs produce massive amounts of concentrated animal manure, typically collected and stored in large lagoons and pits that emit high levels of methane, an especially potent greenhouse gas. Cows in dairy and beef operations also emit methane from their digestive processes, accounting for as much as two-thirds of total global methane emissions. Methane is of particular concern for climate change mitigation. Although it lasts for a shorter lifetime in the atmosphere than carbon dioxide, methane absorbs and radiates twenty-one times more heat energy per molecule than carbon dioxide, making it a serious contributor to climate change and a critical target for overall emissions reduction.[23]


Climate change is one of the most urgent concerns facing contemporary society, and a 2021 United Nations report identified the need to reduce GHG emissions by 2030 to limit global climate change. Crucial to this strategy is reducing emissions from industrial agriculture, which may be up to 90% higher than commonly estimated.[24]

Climate change contributes to 255,000 premature deaths in humans annually, as well as 775,000 asthma-related health complications and 73 billion hours of labor lost due to extreme heat. Worldwide, climate change destroys 26 million tons of crops every year and causes extreme weather events like wildfires, floods, hurricanes, and droughts.


In the US, industrial agriculture is the primary source of pollution in rivers and streams. Manure lagoons overflow and leak, damaging aquatic ecosystems by contaminating local waterways, killing fish, and contributing to harmful bacteria and algae growth. Industrial farms and CAFOs also contaminate local drinking water supplies.[25]

Much global deforestation is to clear land for commercial livestock and their feed crops. Much of the forested land that is key to biodiversity in places like the Amazon rainforest has been appropriated for animal grazing and feed crop production.


Industrial animal agriculture has acute and chronic adverse effects on human health. Residents close to CAFOs suffer from noxious odors and air pollution that causes headaches, respiratory problems, and eye irritation. Particulate matter in the air contributes to asthma, bronchitis, and cardiac arrest.[26]

Workers in CAFOs have a high incidence of debilitating injuries, respiratory ailments, and toxic dust syndrome. CAFOs exude high levels of ammonia and hydrogen sulfide, which cause inflammation of the body’s mucous membranes, chemical burns in the respiratory tract, chronic lung disease, and, in some cases, death.[27]

CAFOs routinely administer antibiotics to animals as a preventive measure that supports weight gain. High levels of subclinical antibiotic use in animals breed antibiotic-resistant strains of bacteria, which present a severe threat to global human health.[28]

Industrial animal agriculture produces meat and other animal products that support high average rates of animal product consumption in the Global North and among wealthy consumers in the Global South. An average person in the US consumes 264 pounds of meat per year. High levels of meat consumption are linked to chronic illnesses like type 2 diabetes, cardiovascular disease, and certain cancers. These diseases are prevalent and severe among the US population, further stressing already overburdened healthcare systems.[29]


Industrial animal agriculture operations are commonly located in rural communities with low socioeconomic status. BIPOC[i] populations are often most severely affected by the presence of CAFOs, leading to lower property values and increased rates of illness. Some studies have shown that property values decline by as much as 88% when CAFOs move into an area.[30]

The cheap, abundant meat produced by industrial animal agriculture provides US society with highly unequal access to meat-based foods. Wealthy consumers and affluent populations can often access healthier, more varied, and higher quality diets, while economically disadvantaged communities face food access disparities and an overabundance of unhealthy, processed animal products. BIPOC communities also experience disproportionately high levels of food insecurity. In 2020, 38 million people went hungry in the US; up to 24% of Black people and up to 20% of Latinx[ii] people in the US faced some degree of food insecurity.


In the US, 41% of all land is used to raise and feed animals, with 127 million acres devoted just to growing animal feed. In addition, more than one-third of agricultural land is used for grazing livestock. By comparison, only 77 million acres of land are used to grow vegetable and fruit crops for direct human consumption. Worldwide, agriculture uses 38% of ice-free land, two-thirds of which is used for grazing.


On an individual basis, reducing consumption of meat, dairy, and eggs can help to mitigate the negative effects of industrial animal agriculture. Routinely choosing plant-based foods can decrease demand for industrially farmed animal products.

At a societal level, reducing global reliance on animal agriculture also necessitates policy changes in the US and elsewhere that focus on food system reform and align with health recommendations for increasing fruit and vegetable consumption. Conventional meat, dairy, and egg production are heavily subsidized by the US government, while farmers who grow fruits and vegetables receive comparatively little support.

Reallocating public agricultural funding and reducing animal product consumption patterns are essential strategies for reforming the US food system to benefit people, animals, and the environment.

[i] Stray Dog Institute uses the term BIPOC to recognize the lived histories of oppression and resistance experienced by Black, Indigenous, and People of Color. This term is not universally embraced, particularly because it can erase the experiences of individual groups by lumping them together. Additionally, the language of this term reflects the specific historical social context of the United States and may not accurately reflect current or past racial and ethnic descriptions elsewhere. We recognize these drawbacks and use the term BIPOC only when a statement is truly applicable to Black, Indigenous, Latinx, Middle Eastern, North African, East Asian, South Asian, Southeast Asian, and Pacific Islander communities in the US. When an experience or condition is applicable only to a specific group, we use specific rather than general language.

[ii] Stray Dog Institute uses Latinx as a gender-neutral alternative to “Latino” or “Latina” to refer to persons of Latin American heritage living in the US. We use this term although we recognize that it simplifies and homogenizes important cultural variations, and individuals may have their own preferred terminology. We honor the importance of the diverse lived experiences of oppression and unique cultural histories of Latin American countries, regions, and peoples.

[1] James M. MacDonald and William D. McBride, “The Transformation of U.S. Livestock Agriculture: Scale, Efficiency, and Risks” (USDA Economic Research Service, January 2009),

[2] Jay P. Graham and Keeve E. Nachman, “Managing Waste from Confined Animal Feeding Operations in the United States: The Need for Sanitary Reform,” Journal of Water Health 8, no. 4 (December 2010): 646–670,

[3] Craig W. Tallentire, Ilkka Leinonen, and Ilias Kyriazakis, “Breeding for Efficiency in the Broiler Chicken: A Review,” Agronomy for Sustainable Development 36 (November 2016),

[4] M-E. Krautwald-Junghanns et al., “Current Approaches to Avoid the Culling of Day-Old Male Chicks in the Layer Industry, with Special Reference to Spectroscopic Methods,” Poultry Science 97, no. 3 (March 2018): 749–757,

[5] James M. MacDonald, Jonathan Law, and Roberto Mosheim, “Consolidation in U.S. Dairy Farming” (USDA Economic Research Service, July 2020),

[6] Devon J. Wilson et al., “Short Communication: Condition of Male Dairy Calves at Auction Markets,” Journal of Dairy Science 103, no, 9 (September 2020): 8530–8534,

[7] Annabelle Beaver, Kathryn L. Proudfoot, and Marina A. G. von Keyserlingk, “Symposium Review: Considerations for the Future of Dairy Cattle Housing: An Animal Welfare Perspective,” Journal of Dairy Science 103, no. 6 (June 2020): 5746–5758,

[8] Hilal Çapar Akyüz and Esin Ebru Onbaşılar, “Non-Infectious Skeletal Disorders in Broilers,” World’s Poultry Science Journal 76, no. 3 (2020): 611–623,

[9] Adele Meluzzi and Federico Sirri, “Welfare of Broiler Chickens,” Journal of Animal Science 8. supp. 1 (2009): 161–173,

[10] Michael J. Toscano et al., “Explanations for Keel Bone Fractures in Laying Hens: Are There Explanations in Addition to Elevated Egg Production?,” Poultry Science 99, no. 9 (September 2020): 4183–4194,

[11] C. C. Whitehead and R. H. Fleming, “Osteoporosis in Cage Layers,” Poultry Science 7, no. 1 (July 2000): 1033–1041,

[12] C. H. Oka et al., “Performance of Commercial Laying Hens Submitted to Different Debeaking Methods,” Brazilian Journal of Poultry Science 19, no. 4 (October–December 2017),

[13] I. Dittrich, M. Gertz, and J. Krieter, “Alterations in Sick Dairy Cows’ Daily Behavioural Patterns,” Heliyon 5, no. 11 (November 2019),

[14] J. F. Mee and L. A. Boyle, “Assessing Whether Dairy Cow Welfare Is “Better” in Pasture-Based than in Confinement-Based Management Systems,” New Zealand Veterinary Journal 68, no. 3 (May 2020): 168–177, https://10.1080/00480169.2020.1721034.

[15] Charlotte Gaillard et al., “Social Housing Improves Dairy Calves’ Performance in Two Cognitive Tests,” PLOS One (February 2014),

[16] Heather W. Neave et al., “Pain and Pessimism: Dairy Calves Exhibit Negative Judgement Bias Following Hot-Iron Disbudding,” PLOS One (December, 2013),

[17] Cassandra B. Tucker et al., “Beef Cattle Welfare in the USA: Identification of Priorities for Future Research,” Animal Health Research Reviews 16, no. 2 (October 2015): 107–124,

[18] Liat Morgan et al., “Physiological and Economic Benefits of Abandoning Invasive Surgical Procedures and Enhancing Animal Welfare in Swine Production,” Scientific Reports  9, no. 1 (November 2019),

[19] Mohamed Rhouma et al., “Post Weaning Diarrhea in Pigs: Risk Factors and Non-Colistin-Based Control Strategies,” Acta Veterinaria Scandinavica 59 (May 2017),

[20] B. Jørgensen, “Influence of Floor Type and Stocking Density on Leg Weakness, Osteochondrosis, and Claw Disorders in Slaughter Pigs,” Animal Science 77, no. 3 (December 2003): 439–449,

[21] Emma M. Baxter, Inger Lise Andersen, and Sandra A. Edwards, “Sow Welfare in the Farrowing Crate and Alternatives,” in Advances in Pig Welfare, ed. Marek Špinka(Cambridge: Woodhead, 2018), 27–72,

[22] Richard Twine, “Emissions from Animal Agriculture—16.5% Is the New Minimum Figure,” Sustainability 13, no. 11 (June 2021),

[23] Elizabeth Bristow and Amy J. Fitzgerald, “Global Climate Change and the Industrial Animal Agriculture Link: The Construction of Risk,” Society and Animals 19, (2011): 205–224,

[24] Matthew N. Hayek and Scot M. Miller, “Underestimates of Methane from Intensively Raised Animals Could Undermine Goals of Sustainable Development,” Environmental Research Letters 16, no. 6 (June 2021),

[25] Javier Mateo-Sagasta et al., “Water Pollution from Agriculture: A Global Review” (Food and Agriculture Organization and International Water Management Institute, 2017),

[26] Carrie Hribar, “Understanding Concentrated Animal Feeding Operations and Their Impact on Communities” (National Association of Local Boards of Health, 2010),

[27] See endnote 26.

[28] See endnote 26.

[29] A. Wolk, “Potential Health Hazards of Eating Red Meat,” Journal of Internal Medicine 281, no. 2 (February 2017): 106–122,

[30] See endnote 26.

About the author

Stray Dog Institute

To cultivate dignity, justice, and sustainability in the food system, Stray Dog Institute provides nonprofit allies with funding, strategic research, and opportunities for collaboration. Together, we hope to build a more compassionate world for people, animals, and the environment.

About the Author

To cultivate dignity, justice, and sustainability in the food system, Stray Dog Institute provides nonprofit allies with funding, strategic research, and opportunities for collaboration. Together, we hope to build a more compassionate world for people, animals, and the environment.

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