When both carotid arteries are properly severed, sheep will lose sensibility within 2 to 14 seconds (Newhook and Blackmore 1982, Gregory and Wotton 1984, Nangeroni and Kennett 1963, Schulz et al 1978, Blackmore 1984). Most sheep will be insensible within 10 seconds. Calves and cattle take a longer period of time to become insensible and they are more likely to have a prolonged period of sensibility. The time to loss of insensibility when good cutting technique is used will range from 17 sec to 85 sec. Some cattle may have prolonged periods of sensibility lasting up to 385 seconds (Blackmore, 1984). Both scientific research and practical experience indicate that cattle have more problems with prolonged periods of sensibility compared to sheep.
Grandin T., Department of Animal Science, Colorado State University, September 2012