Assessing pig welfare at stunning in Swedish commercial abattoirs using CO₂group-stun methods

Abstract

While regular monitoring of stun quality in abattoirs is now required by EU law, guidelines specific to species and stun method have not been adequately developed. Carbon dioxide (CO 2) gas stunning of pigs in groups is widely used because of efficiency and reduced pre-slaughter stress. However, some pigs may recover from the stun process if it is not correctly managed. In light of these concerns, this study aimed to develop and implement a standardised assessment for stun quality for use in commercial pig abattoirs. Eight abattoirs and 9,520 slaughter pigs were assessed for stun group size, stick time and stun quality. The stun system, CO 2 concentrations and exposure times were also investigated. A stun-quality protocol (SQP) identified and risk-rated symptoms signifying recovery of consciousness. In abattoirs using paternoster stun-boxes, pigs consistently showed no stun-quality problems despite 65% with stick times between 70 and 100 s. Stun-quality problems were detected in 1.7 to 3.3% of pigs in abattoirs using dip-lift stun-boxes and 75% of stick times were below 60 s. In 36 of 38 cases of inadequately stunned pigs, a combination of symptoms from the SQP was seen. Regular gasping preceded other symptoms in 31 cases and was a valid indicator of inadequate stunning. In response to the stun-quality assessments, two abattoirs serviced the stun machines (increasing CO 2 concentrations and exposure times). All pigs were adequately stunned in follow-up studies. Implementation of stun-quality assessments, such as developed in this study, can assure monitoring of animal welfare at slaughter, beneficial not only to the industry and relevant authorities but also the concerned consumer.

Hot-water spraying is a sensitive test for signs of life before dressing and scalding in pig abattoirs with carbon dioxide (CO2) stunning

“…However, dwell times and CO 2 concentrations were relatively low in this abattoir, whereas stun-to-stick intervals were rather long. These variables are known to be of crucial importance in preventing SOL (Atkinson et al, 2012;Von Wenzlawowicz et al, 2012;Llonch et al, 2013). In addition, the stick-to-hot water interval was relatively short in this abattoir, possibly increasing the likelihood of SOL at the time of HWS.…”

“…Although these findings are based on pigs from a sole abattoir, recent studies have also found MO to be the predominant indicator for impaired welfare of pigs during bleeding (Atkinson et al, 2012). To our understanding, this underscores the importance of skilled employees who not only monitor the stunning but also the bleeding effectiveness.…”

Animal (De)liberation: Should the Consumption of Animal Products Be Banned?

“…This can happen by various means: an electric current can be applied to the head to cause a grand mal seizure; a bolt can be fired through the skull by means of a captive bolt pistol; or they can be gassed using CO 2 . The use of this last method appears to be increasing, as other methods are deemed to pose greater welfare concerns (Atkinson et al 2012). The pigs are then shackled and hoisted up before being stuck in the neck with a sharp knife that aims to cause the pigs to bleed to death.…”

Assessing unconsciousness in livestock at slaughter

“…Gasping results from a suppression of respiratory-modulated neuronal activities of the pons and a recruitment of medullary mechanisms for gasping (St John, 2009). Atkinson et al (2012) observed that regular gasping (more than 3 times gasping in a 10 s interval) was in some cases the only symptom observed after CO 2 stunning in pigs and animals were considered unconscious in those cases. In other cases, gasping was related to other symptoms indicative for inadequate stunning (e.g.…”

“…This animal was reshot, and this supported the study by , which indicated that when nystagmus was observed, there was a one in three chance that the quality of the stun was insufficient. Nystagmus may occur as a result of electrical stunning (Grandin, 2002), but in CO 2 stunned pigs, nystagmus was not observed once (Atkinson et al, 2012). It is stated that under no circumstances should a stunned animal vocalise, as vocalisation after stunning indicates consciousness and probably distress and pain (Grandin and Smith, 2004;Gouveia et al, 2009).…”