Numerous studies have been conducted to determine the relative stressfulness of different husbandry and slaughter procedures. Measurements of cortisol (stress hormone) is the most common method of evaluating handling stresses. One must remember that cortisol is a time-dependent measure. It takes approximately 15-20 minutes for it to reach its peak value after an animal is stressed. Evaluations of handling and slaughter stress will be more accurate if behavioural reactions, heart rate and other blood chemistries are also measured. Adrenaline and noradrenaline have limited value in measuring slaughtering stress because both captive bolt and electrical stunning trigger massive releases (Warringtom,1974; Pearson et al.,1977; van der Wal,1978). If the stunning method is applied properly the animal will be unconscious when the hormone release occurs and there will be no discomfort.
Absolute comparisons of cortisol levels between studies must be done with great caution. Cortisol levels can vary greatly between individual animals (Ray et al.,1972).
Cattle that show signs of behavioural excitement usually have higher levels than calm animals. A review of many reports indicates that cortisol levels is cattle fall into three basic categories:
- Resting baseline levels.*
- Levels provoked by being held in a race or restraint in a head gate(bail) for blood testing.
- Excessive levels which are double or triple the farm restraint levels.
*Baseline levels vary from a low of
(2 ng ml)-1 (Alam and Dobson,1986)
(9 ng ml)-1 (Mitchell et al.,1988).
Restraining excessively raised semi-wild cattle for blood testing under farm conditions elicits cortisol readings of:
( In some studies cortisol levels were expressed in (nmol 1)-1. These values were converted into (ng ml)-1 by multiplication by 0.36.
- (25-33 ng ml)-1 in steers (Zavy et al.,1992)
- (63 ng ml)-1 in steers and cows (Mitchell et al.,1988)
- (27 ng ml)-1 in steers (Ray et al.,1972)
- (24-46 ng ml)-1 in weaner calves (Crookshank et al.,1979)
Grandin, T. 1994
Euthanasia and Slaughter of Livestock
Journal of American Veterinary Medical Association
volume 204 : 1354 - 1360
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