Pigs are intelligent, sociable and inquisitive animals. Historically pigs were farmed as an additional source of income in the dairy and grain industry, but pig farming has since evolved into its own industry with ~2.4 million pigs currently being farmed in Australia . Pigs farmed for meat may be housed in intensive indoor, semi-indoor (outdoor-bred) or outdoor (free-range) systems. Most pigs in Australia are housed in intensive indoor systems.
Pigs farmed for meat are the offspring of specific breeding animals in a pig herd, which include boars (entire male pigs), gilts (female pigs who have not had a litter of piglets before) and sows (female pigs who have had a litter of piglets). Some piggeries (pig farms) operate exclusively as breeder farms only housing breeding animals. The gestation period (length of pregnancy) of a sow is on average 115 days. Intensive indoor systems involve boars housed in individual pens, and gilts and sows are usually housed in group pens. Group sizes for gilts and sows may vary from small groups (<10 sows) to large groups (>100 sows). In intensive indoor systems, pigs may also be confined in boar stalls, sow stalls, farrowing crates and/or mating stalls. In semi-outdoor and outdoor systems gilts and sows are kept in group paddocks, and boars may be kept in a separate paddock or with the gilts and sows.
When confined, pigs are unable to move freely or perform natural and motivated behaviours such as foraging, interacting socially with other pigs or nesting prior to farrowing. The RSPCA opposes housing systems that confine pigs for any extended period, including the use of boar stalls, sow stalls, mating stalls and farrowing crates. To read more about the animal welfare issues associated with sow stalls and farrowing crates, click here.
The Australian pig industry committed to voluntarily phasing out sow stalls after the first five days following mating (where the gilt or sow is confined to a mating stall) in favour of group housing for pregnant sows by 2017. It is estimated that around 80% of gilts and sows in Australia are now housed in groups. Where sow stalls are still in place, it is a legal requirement that they are not used for more than six weeks during gestation.
Mating of pigs on farm occurs either through natural mating using a boar or artificial insemination. Boars are used for the collection of semen as well as to bring the gilt or sow onto heat (the time when the sow is receptive to being mated), to determine if the gilt or sow is on heat, or to mate naturally.
Artificial insemination is the most common method used in intensive indoor systems. It occurs in mating stalls where the gilt or sow is confined for artificial insemination and remains confined for the first few days after mating before being returned to group housing. In semi-outdoor and outdoor systems, gilts and sows are usually brought into larger mating pens for natural mating or artificial insemination and are then released back into their pen or paddock.
In intensive indoor systems, gilts and sows are moved into farrowing crates around a week before they give birth (farrowing). The farrowing crate confines a sow while allowing piglets access to her teats for feeding and a separate warm area for piglets to move into and avoid being accidentally crushed. Sows remain confined in farrowing crates until piglets are weaned at about three to four weeks of age. The RSPCA opposes the use of farrowing crates.
In semi-outdoor and outdoor systems, pregnant gilts and sows are moved to farrowing huts prior to giving birth in smaller outdoor areas or paddocks. A farrowing hut is usually bedded with straw for nest building and sows are able to move around freely and access their piglets.
Piglets and weaning
On average, a sow will give birth 2.4 times per year with around 9-13 piglets each litter. After piglets are born, they may undergo several painful husbandry procedures in the first few days of life, such as ear tagging or notching, teeth clipping and tail docking. To read more about the welfare issues associated with piglet husbandry procedures, click here.
Piglets remain with their mother until weaning, which is when milk is gradually or abruptly removed from the suckling piglets’ diet at around three to four weeks of age. After weaning piglets are then moved to a grow-out shed on the same farm or transported to a specific grow-out farm. Under natural conditions, piglets would continue to suckle from their mother until they are gradually weaned at around four to five months of age.
Pigs after weaning may be reared (grown out) in intensive indoor, semi-outdoor (deep litter) or outdoor (free-range) housing systems.
In intensive indoor systems, pigs are moved into group pens and moved between different sheds depending on the stage of production. In semi-outdoor systems, pigs are moved into large sheds/barns with bedding such as straw or rice hulls, that may also have access to an outdoor pen area. In outdoor free-range systems, pigs are kept outdoors in paddocks with access to shelter with bedding.
Regardless of the housing system pigs must be provided with adequate space while they are growing so that they are able to move around freely, and all lie down in lateral recumbency (on their sides with legs outstretched) at the same time. Having adequate space is also important for pigs to be able to socialise and escape other pigs when they choose, as well as perform natural and motivated behaviours, such as rooting and foraging. To read more about some of the animal welfare issues associated with pig production, click here.
Pigs are typically raised for five to six months when they weigh around 60kgs after which they are transported on trucks to an abattoir for slaughter.
Upon arrival at the abattoir pigs are unloaded from trucks and moved in group pens where they are provided with water. Prior to slaughter pigs are moved from these pens and walked up a raceway individually or in small groups to be stunned (rendered unconscious). Pigs may be stunned using electrical stunning or carbon dioxide controlled atmosphere stunning systems. After stunning pigs are checked to confirm they are unconscious and unable to feel pain before being bled out, which is done to ensure death before further processing.
Carbon dioxide controlled atmosphere stunning is currently the most common stunning method for pigs in Australian abattoirs. This stunning method can provide some welfare benefits compared to electrical stunning, such as minimal restraint and allowing pigs to remain in groups during handling and stunning. However, there are still a number of animal welfare issues associated with its use because carbon dioxide gas at high concentrations is aversive for pigs. At high concentrations carbon dioxide gas causes respiratory distress and a feeling of breathlessness, as well as irritation and a burning sensation to mucosal membranes (e.g., nostrils and gums) due to being acidic [2, 3]. To read more about the animal welfare issues associated with carbon dioxide controlled atmosphere stunning, click here.
The meat from pigs produced in Australia is typically used in fresh pork products as well as processed products including bacon and ham. However, the majority of bacon, ham and other cured pork products in Australia are imported and therefore do not necessarily come from pigs that have been raised to the same welfare standards as pigs in Australia. To learn more about the animal welfare issues associated with imported pork, click here.
When sows and boars reach the end of their productive breeding life they are also transported to an abattoir for slaughter. However, due to the much larger size of sows and boars compared to grower pigs, they are typically stunned using a penetrating captive bolt prior to slaughter. The meat from sows and boars is more commonly used in cured pork products (e.g., salami) or further processed products.
 Lechner I, Leger A, Zimmermann A et al. (2021) Discomfort period of fattening pigs and sows stunned with CO2: Duration and potential influencing factors in a commercial setting. Meat Science 179, 108535.