Assessment of the efficiency of captive-bolt stunning in cattle and feasibility of associated behavioural signs
Efficient stunning is essential for the welfare of animals destined for slaughter. Several studies have dictated certain signs as reliable for the assessment of stunning efficiency in cattle. However, there is still a lack of data concerning the viability of these signs. The aim of
the following study was to assess stunning efficiency at a slaughterhouse, studying the relationship between age, sex and breed of cattle and the efficiency of stunning and determining the feasibility of the following signs in assessing stunning efficiency: immediate collapse, muscle spasms,
rhythmic breathing, rotation of the eyeballs, painful response to ear or nose pinch, vocalisation and muscle tone of the ears. Cattle were observed immediately after stunning and hoisting onto the bleed rail. Results showed that stunning efficiency decreased with age, was greater in females
than males (for animals greater than 12 months of age) and was superior in 'dairy' compared to 'beef' cattle at all age ranges. Presence of ear muscle tone, absence of muscular spasms, presence of rhythmic breathing, and vocalisation were the most common signs of inefficient stunning recorded
in the present study. Recognition of the most frequently occurring signs associated with inefficient stunning will point out the need for re-stunning, preventing animals from regaining sensibility.