Slaughter

Pigs are usually slaughtered after 4-7 months. Pigs intended for pork are usually slaughtered 1-2 months younger than pigs for bacon. Almost 9.8 million pigs were slaughtered in the UK in 2011, (9.5 million in 2010)(1).

Pigs are stunned first then killed by being shackled and hoisted before having the blood vessels in their throat slit (sticking). The animal dies by being bled to death. Pigs are usually stunned electrically whereby an electric current is applied by means of two electrodes in the form of tongs. These are placed on either side of the brain, usually either side of the neck behind the ears so that sufficient current is passed through it. The current should induce a state of immediate epilepsy (electroplectic shock) in the brain, during which time the animal is unconscious(8). A survey of pig slaughtering procedures was carried out in the UK by Anil and McKinstry in 1993, Bristol University (9).

The factors affecting slaughter included the placement of tongs on the animal, the average current strength passed through the animal’s brain and also the length of time that the tongs are in place for. The survey showed that a significant percentage of the tong applications observed in the traditional stunning pen did not span the brain. This would result in animals not being stunned adequately and also lead to many pigs regaining consciousness during bleeding out or even before throat-slitting. Some pigs may be re-stunned due to the initial stunning failure and to suppress the spontaneous kicking to aid the hoisting and shackling of the animals. This also reduces the interval of the stunning-to-sticking and helps prevent the incidence of inadequate sticking as it is more difficult to stick a kicking/convulsing animal.

Anil & McKinstry’s Survey found variations in the methods and effectiveness of sticking. Sometimes the first attempt at sticking the stunned pigs on the shackle line did not always result in a rapid and profuse loss of blood with a second sticking attempt required for 2.3% of pigs. Some pigs showed signs of recovery during the bleed out. The results of a study carried out by Anil et al (2000) (10) showed that following head-only electrical stunning, a relatively long sticking wound by a thoracic cut (chest sticking) should result in humane slaughter and provide better welfare in slaughter pigs. Other factors which should be taken into account regarding the welfare of pigs at slaughter includes; operator error as a result of high throughput, tiredness, insufficient instructions, animal position and inadequate knives.

Some pigs may be stunned using carbon dioxide gas. This is less common in the UK but widely used in other countries such as Denmark. Approximately 1/3 of pigs in the UK are killed by this method (11). Pigs are passed through a well containing an atmosphere of carbon dioxide (70-90%) and air. The pigs are rendered unconscious due to the acidification of the cerebrospinal fluid upon inhalation of the carbon dioxide. This method eliminates the human element required in electric stunning but has been strongly criticised by scientists as inhumane, with pigs suffering from breathlessness and hyperventilation (11).

< Previous | Next >  1 | 2 | 3 | 4 | 5