Histogram showing the incidence of vocalisation in 5-day old lambs in the 90 minutes after different rubber ring castration and tail docking techniques.

Molony et al (2002)

CTD - Bilateral castration and tail docking

C2   - Bilateral castration

C1   - Unilateral castration

C0   - Short scrotum castration

LA   - Short scrotum castration plus local anaesthetic

 H    - Handled control lambs

TD   - Tail docked only

Castrated and tail docked lambs showed significantly more vocalisation than all other treated lambs, except short scrotum treated lambs.  Loud open-mouthed vocalisations and soft groans were recorded equally.  The wide variation in vocalisation between individuals within the same treatment group makes it less useful as a measure for the presence of pain.  Most of the vocalisation occurred during the first 30 minutes after treatment (mean maximum of eight calls per six minute period).   However, lambs in all treatment groups, including control lambs, also showed a higher incidence of vocalisation immediately after handling to treat or collect a blood sample (taken every 12 minutes up to 96 minutes - see graphs below).  This response to handling suggests that it is important to separate different forms of vocalisation used by the lamb.