Slaughter without stunning is controversial from an animal welfare standpoint. When this subject is being discussed it is essential to consider species differences between cattle and sheep. Welfare issues are greater for cattle because they take longer to become unconscious compared to sheep. When both carotid arteries are severed, sheep will lose sensibility within 2 to 14 seconds (Newhook and Blackmore 1982, Gregory and Wotton 1984). Calves and cattle take a longer period of time to become insensible and they are more likely to have a prolonged period of insensibility. The time to loss of insensibility when good cutting technique is used will range from 17 sec to 85 sec (Blackmore 1984, Blackmore et al 1983l, Gregory and Wotton, 1984, Grandin 2010, Daly et al 1988, Gregory et al 2010). Some cattle may have prolonged periods of sensibility lasting up to 385 seconds (Blackmore, 1984). When good technique is used the average time to collapse is 17 seconds (Grandin 2910). Both scientific research and practical experience indicate that cattle have more problems with prolonged periods of sensibility compared to sheep. Another problem in cattle is occlusion of the carotids which can occur after the act (Gregory 2010). This problem is less likely to occur in sheep and goats. Occlusions caused by false aneuryms do not occur in sheep and goats (N. Gregory, Personal Communication in 2011).
The main reason for the differences between cattle and sheep is due to differences in the anatomy of the blood vessels that supply the brain (Baldwin and Bell, 1963 a,b,c; and Blackman et al, 1986). When slaughter without stunning is done, both carotid arteries are cut. In sheep the carotid arteries that are located in the front of the throat provide the brain with it’s entire supply of blood. In cattle the vertebral arteries which are not severed by the cut also supply the brain with blood. Therefore, when the carotids are severed in cattle the brain still has a blood supply. The differences in the blood supply to the brain of sheep and cattle have been researched in detail (Baldwin and Bell 1963 a,b,c,d).
Grandin T., Department of Animal Science, Colorado State University, Updated Sept. 2012
