Epsilon Open Archive

Abstract

This thesis aimed to develop and implement a standardised assessment for stun quality for use in commercial pig and cattle abattoirs to protect animal welfare. A stun quality protocol identified and rated symptoms signifying recovery risk and level of concern for inferior animal welfare. The thesis also aimed to identify problem areas and methods for improving animal welfare standards at slaughter.

Eighteen assessments were conducted on 9520 pigs stunned with CO₂ gas and 2725 cattle stunned with penetrating bolt concussion stunners.

For pigs, insufficient CO₂ exposure times and concentrations contributed to a small percentage of pigs being inadequately stunned in three abattoirs using dip-lift systems; rectifying these elements resulted in 100% adequate stunning during follow-up studies.

In the studies in cattle abattoirs, bulls were found to be significantly more likely to be inadequately stunned than other cattle types (heifers, cows and steers). Risk factors identified as contributing to a higher frequency of inadequate stunning included inappropriately designed loading and stun-box facilities, use of cartridge fired stunners that were too low in power for bulls, poor maintenance of stunners, inappropriate ammunition storage and the lack of neck restraints to prevent inaccurate shooting. Stun quality was optimised by the use of a Jarvis® pneumatic stunner in combination with neck restraints.

Based on the display of different symptoms, the brains of twelve cattle were macroscopically analysed in two of the abattoirs studied, with the level of brain haemorrhage and tissue damage corresponding to the adequacy of the stun.
The use of protocols such as those developed in this study can help standardise stun quality assessments and allow for benchmarking of stun quality at commercial slaughter. This can help to ensure that animal welfare standards are met. The conclusions of this thesis will be of interest and relevance to the commercial abattoirs and relevant authorities globally.