Part 1: Assessment of upright restraint of broilers for head-only electrical stunning

Abstract

The welfare issues associated with water-bath stunning, particularly inversion and shackling, are widely recognised. This study aimed to develop, optimise and evaluate a prototype upright restraint system for broilers that avoids inversion and shackling of conscious birds. The device consisted of a horizontal conveyor with paired vertical side-belts fitted with rubber fingers to conform to the bird’s body, restraining the bird and preventing flapping. Fifty slaughter-weight broilers (1.7–3.6 kg) underwent up to five restraint runs each while behavioural indicators of distress, discomfort, trauma and positioning outcomes were assessed. Iterative design changes improved presentation, moving the side-belts closer, increased the odds of normal-like rhythmic breathing and removing the top finger row reduced head withdrawal. There were no overt signs of severe distress or trauma; however, vocalisations increased with run number. Repeated exposure may have influenced responses through habituation or sensitisation. However, in commercial use, birds would enter the device only once to be stunned and bled, so multi-run observations should not be over-generalised to slaughter conditions. These findings support the proof of concept for upright restraint as an improved welfare alternative compared to inversion-based systems for broilers.