Histogram showing peak plasma cortisol values in lambs less than a week of age after different methods of castration and tail docking.

Note that lambs tail docked with rubber rings had lower increases in cortisol values (65 nmol/l) than ring castrated lambs (about 170 nmol/l).  Lambs bilaterally castrated with and without tail docking using a combined Burdizzo rubber ring method (Kent et al 1995, 1998) had significantly lower increases in acute plasma cortisol peak values (95 and 60 nmol/l respectively) than the equivalent treatments without the crushing action of the Burdizzo to destroy the nerves and so preventing the transmission of nerve impulses to the brain from the tissue below the ring. These results suggest that the combined Burdizzo rubber ring method of castration and tail docking may be less acutely painful than rubber ring castration and tail docking.

Although plasma cortisol is not a good parameter for assessing differences in severity between treatments that result in severe pain, it appears better for comparing treatments that result in moderate or mild pain.