The use of sow stalls for pregnant sows has resulted in lower birth production costs, however, this practice has led to more significant animal welfare concerns. Many of the world’s largest producers of pigs (U.S., Canada, Denmark) use sow stalls, but some nations (e.g., the UK) and some US States (e.g., Florida and Arizona) have banned them.
Pigs are naturally omnivorous and are generally fed a combination of grains and protein sources (soybeans, or meat and bone meal). Larger intensive pig farms may be surrounded by farmland where feed-grain crops are grown. Alternatively, piggeries are reliant on the grains industry. Pig feed may be bought packaged or mixed on-site. The intensive piggery system, where pigs are confined in individual stalls, allows each pig to be allotted a portion of feed. The individual feeding system also facilitates individual medication of pigs through feed. This has more significance to intensive farming methods, as the close proximity to other animals enables diseases to spread more rapidly. To prevent disease spreading and encourage growth, drug programs such as antibiotics, vitamins, hormones and other supplements are preemptively administered.
Indoor systems, especially stalls and pens (i.e., ‘dry,’ not straw-lined systems) allow for the easy collection of waste. In an indoor intensive pig farm, manure can be managed through a lagoon system or other waste-management system. However, waste smell remains a problem which is difficult to manage.
The way animals are housed in intensive systems varies. Breeding sows will spend the bulk of their time in sow stalls (also called gestation crates) during pregnancy or farrowing crates, with litter, until market.
Piglets can be subjected to a range of treatments including castration, tail docking to reduce tail biting, teeth clipped (to reduce injuring their mother's nipples) and their ears notched to assist identification. Treatments are usually made without pain killers. Weak runts may be slain shortly after birth.
Piglets also may be weaned and removed from the sows at between two and five weeks old and placed in sheds. However, grower pigs - which comprise the bulk of the herd - are usually housed in alternative indoor housing, such as batch pens. During pregnancy, the use of a stall may be preferred as it facilitates feed-management and growth control. It also prevents pig aggression (e.g., tail biting, ear biting, vulva biting, food stealing). Group pens generally require higher stockmanship skills. Such pens will usually not contain straw or other material. Alternatively, a straw-lined shed may house a larger group (i.e., not batched) in age groups.
Many countries have introduced laws to regulate treatment of farmed animals. In the USA, the federal Humane Slaughter Act requires pigs to be stunned before slaughter, although compliance and enforcement is questioned. There is concern from animal liberation/welfare groups that the laws have not resulted in a prevention of animal suffering and that there are "repeated violations of the Humane Slaughter Act at dozens of slaughterhouses".
Transition of an indoor production system to an outdoor system presents obstacles. Some breeds of pig commonly used in intensive farming have been selectively bred to suit intensive conditions. Lean pink-pigmented pigs are unsuited for outdoor agriculture, as they suffer sunburn and heat stress. In certain environmental conditions – for example, a temperate climate – outdoor pig farming of these breeds is possible. However, there are many other breeds of pig suited to outdoor rearing, as they have been used in this way for centuries, such as Gloucester Old Spot and Oxford Forest. Following the UK ban of sow stalls, the British Pig Executive indicates that the pig farming industry in the UK has declined.. The increase in production costs has led to British pig-products being more expensive than those from other countries, leading to increased imports and the need to position UK pork as a product deserving a price premium.
A ‘sow stall’ is the name of the confinement system for adult sows. It usually does not allow the pig to turn around, although it can sit or lie down The major reason for their use is that it prevents attacks towards pregnant sows, thus reducing miscarriages and increasing litter survival and the farmer’s productivity.
Only the sows selected for breeding (i.e., pregnant sows) will spend time in a sow stall. In an intensive system, the sow will be placed in a stall prior to service (mating) and will stay there for at least the start of her pregnancy, where the risk of miscarriage is higher. The length of the sow's gestation is 3 months, 3 weeks, and 3 days. In certain cases, sows may spend this time in the crate. However, a variety of farming systems are used and the time in the crate may vary from 4 weeks to the whole pregnancy.
There is also some criticism of 'farrowing crates'. A farrowing crate houses the sow in one section and her piglets in another. It allows the sow to lie down and turn around to feed her piglets, but keeps her piglets in a separate section. This prevents the large sow from sitting on her piglets and killing them, which is quite common where the sow is not separated from the piglets. Some models of farrowing crates may allow more space than others, and allow greater interaction between sow and young, although these increase the chance that the sow will crush her piglets. Some crates may also be designed with cost-effectiveness or efficiency in mind and therefore be smaller.