A hog farm is an agricultural operation that raises pigs for meat production, typically moving animals through distinct growth stages from birth to a market weight of 180 pounds or more. These farms range from small pasture-based operations with a few hundred animals to industrial-scale facilities housing thousands of pigs in climate-controlled buildings. Most commercial pork in the United States comes from larger, specialized operations known as concentrated animal feeding operations, or CAFOs.
How Hog Farms Are Classified by Size
The EPA classifies hog farms based on the number of animals they hold. A large CAFO houses 2,500 or more pigs weighing over 55 pounds, or 10,000 or more younger pigs under 55 pounds. Medium operations fall between 750 and 2,499 adult-weight pigs, and small farms keep fewer than 750. These classifications matter because larger operations face stricter federal regulations around waste discharge and water quality. A small farm with a few hundred pigs on pasture operates under a very different regulatory framework than a facility finishing thousands of hogs indoors.
The Production Lifecycle
Pigs on a commercial hog farm move through a sequence of stages, each with its own housing and nutritional requirements. The cycle begins with breeding sows, which carry piglets for about 114 days (roughly three months, three weeks, and three days, as farmers often say). After birth, piglets nurse for anywhere from two to five weeks before weaning, depending on the operation. Niche and pasture-raised farms often keep piglets with the sow for five weeks or longer.
After weaning, young pigs move to a nursery phase where they’re fed specialized starter diets and kept in warm, controlled environments. From there, they transition to the finishing phase, where they eat high-energy rations and gain weight rapidly. A pig typically reaches market weight at around 180 days of age, or roughly six months. The entire cycle, from breeding to slaughter, takes about 10 months when you include the sow’s gestation period.
What Pigs Eat
The backbone of a commercial pig diet is corn and soybean meal, which together provide the calories and protein pigs need to grow efficiently. A typical gestating sow diet, for example, is about 83% corn and 13% soybean meal, with the remainder made up of calcium and phosphorus supplements, salt, and vitamin and mineral premixes. Some farms substitute barley, sorghum, or canola meal depending on local availability and price.
Feed is the single largest cost on a hog farm, so producers track feed conversion closely: how many pounds of feed it takes to produce a pound of weight gain. Corn-and-soy diets contain roughly 1,450 to 1,500 kilocalories of usable energy per pound, and modern genetics combined with precise nutrition have steadily improved conversion rates over the decades.
Housing and Animal Welfare
Most commercial hog farms in the U.S. raise pigs indoors in large, ventilated barns with concrete or slatted floors. The most debated aspect of hog farm housing involves breeding sows. Traditionally, pregnant sows were kept in individual stalls (often called gestation crates) roughly two feet wide, which prevent the sow from turning around. These stalls make it easy to manage feeding and prevent sows from injuring each other, but they restrict nearly all natural movement. Research from the USDA shows that stall-confined sows develop weaker bones, reduced heart function, more lameness, and more pressure sores on their skin compared to sows in open pens.
Group housing gives sows room to walk, root, and socialize, and lameness rates drop, especially when bedding like straw is provided. The tradeoff is more aggression-related skin injuries as sows establish social hierarchies. The European Union has banned gestation stalls, and several U.S. states have followed with similar restrictions, pushing the industry toward group pen systems.
Finishing pigs are typically housed in groups in large pens with slatted floors. Manure falls through the slats into a pit or channel below, which keeps the living surface relatively clean and channels waste toward the farm’s manure management system.
Waste Management
A single finishing pig produces several gallons of manure and urine daily, so waste management is one of the defining engineering challenges of a hog farm. Most operations in the southeastern U.S. and many elsewhere use anaerobic lagoons: large, lined earthen basins where manure is stored as a liquid. Bacteria that thrive without oxygen break down the organic material over time. After a year in a lagoon, about 73% of the volatile organic solids are destroyed. After five years, that figure reaches roughly 80%.
The liquid from these lagoons serves double duty. Surface water (called supernatant) is recycled back into the barns to flush manure channels. The rest is pumped out and sprayed onto nearby crop fields or pastures as fertilizer, delivering nitrogen and phosphorus to growing plants. Timing these applications to match crop nutrient needs is critical. Overapplication can lead to nutrient runoff into waterways, which is the primary environmental concern regulators monitor. Accumulated sludge at the bottom of lagoons needs to be agitated and removed every three to five years, then spread on cropland using specialized irrigation equipment.
Air Quality and Odor
The smell of a hog farm is unmistakable, and it comes from a complex stew of 60 to 150 different chemical compounds produced during the breakdown of manure. The most notable gases are ammonia (a sharp, pungent smell) and hydrogen sulfide (the classic rotten-egg odor). Inside barns, recommended maximum concentrations are 15 parts per million for ammonia and just 3 parts per million for hydrogen sulfide, since both can harm pig and worker health at higher levels.
Ammonia tends to rise quickly and disperses in the atmosphere, so it’s less of an issue for distant neighbors than the heavier, slower-moving odor compounds like volatile fatty acids and mercaptans. For surrounding communities, odor is often the most contentious issue associated with hog farming, and it’s one reason zoning laws frequently require buffer distances between large operations and residential areas.
Biosecurity on Hog Farms
Disease prevention drives much of the daily routine on a modern hog farm. Pigs are vulnerable to highly contagious diseases like porcine reproductive and respiratory syndrome (PRRS) and African swine fever, which can devastate a herd in days. To keep pathogens out, farms establish strict boundaries between “clean” and “dirty” zones. Visitors and workers entering a pig area are typically required to step through a disinfectant footbath, change into clean coveralls, and wear farm-provided boots.
After visiting any location with other pigs, farmers are advised to shower, change clothes, clean and disinfect their shoes and vehicles, and wait overnight before returning to work with their own animals. These protocols might seem extreme, but a single disease outbreak can kill hundreds or thousands of pigs and spread to neighboring farms within days.
Key Regulations
Hog farms operate under several layers of federal and state regulation. The Swine Health Protection Act makes it illegal to feed raw food waste (garbage) to pigs unless that waste has been heat-treated at a licensed facility to kill disease organisms. This law exists because untreated food scraps, particularly those containing meat, can carry viruses like foot-and-mouth disease and classical swine fever. Household food scraps fed to pigs on the same property where the household is located are exempt.
On the antibiotic front, the FDA eliminated the use of medically important antibiotics for growth promotion in livestock. Producers can no longer add these drugs to feed or water simply to make pigs grow faster. Any remaining therapeutic use, whether for prevention, control, or treatment of a specific disease, now requires authorization from a licensed veterinarian under the Veterinary Feed Directive. This shift was designed to slow the development of antibiotic-resistant bacteria that can affect human health.
Environmental regulations add another layer. Large and medium CAFOs must manage their waste discharge under Clean Water Act permits, which typically require nutrient management plans specifying how and when lagoon contents can be applied to fields. State-level rules often add air quality standards, setback distances from property lines, and requirements for lagoon construction and maintenance.