Farming pigs

Breeding females (known as ‘sows’) will be housed indoors indefinitely. They are first impregnated at just 6-8 months old via artificial insemination and will spend most of their lives pregnant: a near-constant cycle of birth and having their babies taken away at just 3-4 weeks of age so that she can be impregnated again. 

Until 1999, sows in the UK were confined to ‘sow stalls’ for their entire lives. These stalls were so small that she could not turn around or interact with others and were completely barren – just a metal frame with bars. These are still legal in lots of other countries, including some from which the UK increasingly imports ‘pork’, with two-thirds of ‘pork’ imports coming from conditions that are illegal in the UK.  

‘Farrowing’ is the process of pigs giving birth. While sow stalls were banned in 1999, pigs can still be confined to ‘farrowing crates’ for the duration of this process – from around 5 days before she is due to give birth until her piglets are weaned at around 28 days old. These crates are typically metal and concrete, completely barren, and so small that the mother cannot turn around or tend to her babies – she is denied every opportunity to perform natural, maternal behaviours like nesting. 60% of sows in the UK are confined to farrowing crates during this sensitive period. 

The natural weaning process for piglets is 2-3 months but on farms this is cut to just 3-4 weeks so that the mother can be impregnated again. This causes emotional trauma for both mothers and babies as well as the physical toll, leading to brittle bones, lameness and weakened immune systems. As highly intelligent animals, pigs suffer greatly when unable to perform natural behaviours and confined to barren environments, leading to behaviours like biting the bars of their crates. These behaviours (similar to the pacing of animals in zoos or the excessive grooming of primates in laboratories) are known as ‘stereotypies’ and indicate complete mental collapse.  

The 40% of sows not confined to farrowing crates will instead farrow outdoors, in individual units typically made of corrugated metal ‘arcs’. While she is free to come and go, her piglets will still be weaned too early (at 3-4 weeks of age) and only 2% of them will remain outdoors until slaughter – the rest will be moved to intensive, indoor ‘finishing’ units and will never see their mother again. 

At least 1 in 6 piglets (16%) will die before they reach the commercial weaning age of 3-4 weeks. Those who survive will be separated from their mother and placed in group pens. Desperate for their mother’s teats, piglets may try to suckle their young penmates or, as they grow older and become increasingly frustrated by their barren surroundings, become aggressive towards each other. Research has found that instances of tail biting and cannibalism is linked to severe boredom, poor diets and bad air quality, and is not a behaviour seen in sanctuaries or in the wild.  

The industry’s solution? To mutilate the piglets by amputating their tails and clipping their teeth, often without anaesthetic. Teeth clipping is also carried out to prevent injury to the sow’s teats, but this avoids the real problem of litter sizes: in natural conditions, a sow would have 4-5 piglets but selective breeding on modern farms has produced standard litters of 10 or more piglets, forcing them to compete and fight for access to teats.

After around 6 weeks, the young pigs are moved to new pens or farms, where they’ll be ‘fattened’ by a high-protein diet aimed at getting them ready for slaughter as soon as possible. Almost all pigs, even if born and weaned outside, will spend their final weeks in indoor finishing units. The main objective of these units is for the pigs to gain weight as rapidly as possible, even when their bodies cannot withstand it. Leg deformities, heart and respiratory problems are all common and worsened by overcrowded, dirty conditions.  

With as little as 1m2 of space for each 100kg pig, crowding can quickly lead to heat stress. In natural conditions, pigs would wallow in mud to lower their temperatures (because they cannot sweat like humans do) but without access to mud or nesting materials, pigs in finishing units are left to wallow in their own excrement.

Government guidelines state that “all pigs must have permanent access to enrichment materials” but these are often token gestures like a chain hanging from the ceiling. As intelligent and emotionally sensitive beings, it’s difficult to overstate the extreme stress that farmed pigs endure. This is heightened further by the long journey to slaughter: some pigs will die en route due to the stress caused by overcrowding, handling, extreme temperatures, and unfamiliar noises. And journeys can also be long. For example, pigs can be transported for 24 hours before making a ‘rest’ stop, followed by another 24 hour stretch.

After 3-4 years of relentless exploitation, the breeding females (as well as breeding boars) are considered ‘spent’ and sent to slaughter. Her babies, meanwhile – if not selected for breeding themselves – will be sent to slaughter at around 5-6 months of age. The natural lifespan of a pig is 12-18 years. 

Of the 10 million pigs killed in UK slaughterhouses every year, the overwhelming majority (88%) are killed using a high concentration of CO2. Small groups of pigs are corralled into revolving metal cages that are then lowered into an atmosphere that is 80-90% CO2. The justification of using CO2 is that it limits stressful handling and the risk of improper stunning, but pigs still suffer tremendously both before entering the gas and during. Pigs have been reported screaming and thrashing around violently as the gas burns their eyes, nostrils and lungs. As far back as 2003, the Farm Animal Welfare Council wanted to see this method phased out but since then, its use has only increased from about one third to almost 90%.  

The remaining 12% of pigs are killed by an electric shock to their heads (an attempt to render them ‘insensible’ to pain) before their throats are cut with a knife. However, electrical stunning is reversible and prone to errors. For example, our investigation into British slaughterhouses found breaches in almost every single one that used this method. Risks include the stunning equipment not being used properly, instead administering an agonising shock instead, or animals being left for too long and regaining consciousness.