Graph showing changes in the plasma cortisol values in the three hours after castrating and tail docking lambs less than a week of age with different methods.
Note how important it is to take regular blood samples during at least the first three hours after treatment, if accurate assessment of the effect of different methods of treatment is to be achieved.
Mean plasma cortisol values in handled control lambs remained below 70 nmol/l throughout the three hour period. Methods involving surgical removal of the testes or crushing the cord without breaking the skin (Burdizzo) produce an early rise in plasma cortisol, peaking within 24 minutes of treatment (surgery peaked at 198 nmol/l, combined Burdizzo rubber ring at 158 nmol/l). This compares with the later peak between 36 and 60 minutes for rubber ring treated lambs (mean peak height about 200 nmol/l). The cortisol values in combined Burdizzo rubber ring treated lambs return to normal by 60 minutes after treatment, compared with 96 to 132 minutes for rubber ring treated lambs. Values in surgically castrated lambs had not returned to normal within the three hour observation period and Lester et al (1991a,b) showed that it can be as long as eight hours before plasma cortisol values return to normal after this method of castration and docking.
